Measurement of σ(e+e−→π+π−) from threshold to 0.85 GeV2 using initial state radiation with the KLOE detector

2011

Measurement of σ(e+e−→π+π−) from threshold to 0.85 GeV2 using initial state radiation with the KLOE detector

Updated measurement of the τ lepton lifetime

1997

A new measurement of the mean lifetime of the tau lepton is presented. Three different analysis methods are applied to a sample of 90000 tau pairs, collected in 1993 and 1994 with the ALEPH detector at LEP. The average of this measurement and those previously published by ALEPH is tau_tau = 290.1 +- 1.5 +- 1.1 fs.

Measurement of the absolute branching fraction for Λc+→Λμ+νμ

2017

Abstract We report the first measurement of the absolute branching fraction for Λ c + → Λ μ + ν μ . This measurement is based on a sample of e + e − annihilation data produced at a center-of-mass energy s = 4.6  GeV , collected with the BESIII detector at the BEPCII storage rings. The sample corresponds to an integrated luminosity of 567  pb − 1 . The branching fraction is determined to be B ( Λ c + → Λ μ + ν μ ) = ( 3.49 ± 0.46 ( stat ) ± 0.27 ( syst ) ) % . In addition, we calculate the ratio B ( Λ c + → Λ μ + ν μ ) / B ( Λ c + → Λ e + ν e ) to be 0.96 ± 0.16 ( stat ) ± 0.04 ( syst ) .

Studies of Quantum Chromodynamics with the ALEPH Detector

1998

Previously published and as vet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant. tests of its flavour independence, tests of the SU(3) gauge structure of QCD, study of coherence effects, and measurements of single-particle inclusive distributions and two-particle correlations for many identified baryons and mesons. (C) 1998 Elsevier Science B.V.

Search for the charged lepton flavor violating decay J/ψ→eτ

2021

A search for the charged lepton flavor violating decay J/ψ→e±τ∓ with τ∓→π∓π0ντ is performed with about 10×109 J/ψ events collected with the BESIII detector at the BEPCII. No significant signal is observed, and an upper limit is set on the branching fraction B(J/ψ→e±τ∓)<7.5×10−8 at the 90% confidence level. This improves the previously published limit by two orders of magnitude.

Four-jet final state production in e+e- collisions at centre-of-mass energies of 130 and 136 GeV

1996

The four-jet final state is analyzed to search for hadronic decays of pair-produced heavy particles. The analysis uses the ALEPH data collected at LEP in November 1995 at centre-of-mass energies of 130 and 136 GeV, corresponding to a total integrated luminosity of 5.7 pb(-1). An excess of four-jet events is observed with respect to the standard model predictions. In addition, these events exhibit an enhancement in the sum of the two di-jet masses around 105 GeV/c(2). The properties of these events are studied and compared to the expectations from standard processes and to pair production hypotheses. RI ANTONELLI, ANTONELLA/C-6238-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-…

Measurement of the branching ratio and search for a CP violating asymmetry in the η→π+π−e+e−(γ) decay at KLOE

2009

Abstract We have studied the η → π + π − e + e − ( γ ) decay using about 1.7 fb − 1 collected by the KLOE experiment at the DAΦNE ϕ -factory. This corresponds to about 72 millions η mesons produced in ϕ radiative decays. We have measured the branching ratio, inclusive of radiative effects, with 4% accuracy: BR ( η → π + π − e + e − ( γ ) ) = ( 26.8 ± 0.9 Stat . ± 0.7 Syst . ) × 10 − 5 . We have obtained the first measurement of the CP-odd ππ – ee decay planes angular asymmetry, A ϕ = ( − 0.6 ± 2.5 Stat . ± 1.8 Syst . ) × 10 − 2 .

Observation of e+e−→ϕχc1 and ϕχc2 at s=4.600  GeV

2018

Using a data sample collected with the BESIII detector operating at the BEPCII storage ring at a center-of-mass energy of root s = 4.600 GeV, we search for the production of e(+)e(-) -> phi chi( ...

Determination of Strong-Phase Parameters in D→KS,L0π+π−

2020

We report the most precise measurements to date of the strong-phase parameters between D^{0} and D[over ¯]^{0} decays to K_{S,L}^{0}π^{+}π^{-} using a sample of 2.93  fb^{-1} of e^{+}e^{-} annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider. Our results provide the key inputs for a binned model-independent determination of the Cabibbo-Kobayashi-Maskawa angle γ/ϕ_{3} with B decays. Using our results, the decay model sensitivity to the γ/ϕ_{3} measurement is expected to be between 0.7° and 1.2°, approximately a factor of three smaller than that achievable with previous measurements, based on the studies of the simulated data. The…

A measurement of the inclusive b → sγ branching ratio

1998

The flavour changing neutral current decay b --> s gamma has been detected in hadronic Z decays collected by ALEPH at LEP. The signal is isolated in lifetime-tagged b (b) over bar events by the presence of a hard photon associated with a system of high momentum and high rapidity hadrons. The background processes are normalised from the data themselves. The inclusive branching ratio is measured to be (3.11 +/- 0.80(stat) +/- 0.72(syst)) x 10(-4), consistent with the Standard Model expectation via penguin processes. (C) 1998 Published by Elsevier Science B.V. All rights reserved. The flavour changing neutral current decay b → sγ has been detected in hadronic Z decays collected by ALEPH at …

Search for the Bc meson in hadronic Z decays

1997

A search for the B-c meson decaying into the channels J/psi pi(+) and J/psi l(+)nu(l) (l = e or mu) is performed in a sample of 3.9 million hadronic Z decays collected by the ALEPH detector. This search results in the observation of 0 and 2 candidates in each of these channels, respectively, while 0.44 and 0.81 background events are expected. The following 90% confidence level upper limits are derived: Br(Z --> BcX)/Br(Z --> q (q) over bar BR(B-c(+) --> J/psi pi(+)) BcX)/Br(Z-->q (q) over bar)Br(B-c(+) --> J/psi l(+)nu) J/psi(e(+)e(-))mu(+)nu(mu) candidate with very low background probability, found in an independent analysis, is also described in detail. (C) 1997 Published by Elsevier Scie…

Search for new hadronic decays of hc and observation of hc→K+K−π+π−π0

2020

Ten hadronic final states of the h(c) decays are investigated via the process psi(3686) -> pi(0)h(c), using a data sample of (448.1 +/- 2.9) x 10(6) psi(3686) events collected with the BESIII de ...

The magnet of the scattering and neutrino detector for the SHiP experiment at CERN

2019

The Search for Hidden Particles (SHiP) experiment proposal at CERN demands a dedicated dipole magnet for its scattering and neutrino detector. This requires a very large volume to be uniformly magnetized at B > 1.2 T, with constraints regarding the inner instrumented volume as well as the external region, where no massive structures are allowed and only an extremely low stray field is admitted. In this paper we report the main technical challenges and the relevant design options providing a comprehensive design for the magnet of the SHiP Scattering and Neutrino Detector.

Measurement of the W mass in e(+)e(-) collisions at production threshold

1997

In June 1996, the LEP centre-of-mass energy was raised to 161 GeV. Pair production of W bosons in e(+)e(-) collisions was observed for the first time by the LEP experiments. An integrated luminosity of 11 pb(-1) was recorded in the ALEPH detector, in which WW candidate events were observed. In 6 events both Ws decay leptonically. In 16 events, one W decays leptonically, the other into hadrons. In the channel where both Ws decay into hadrons, a signal was separated from the large background by means of several multi-variate analyses. The W pair cross-section is measured to be sigma(ww) = 4.23 +/- 0.73(stat.) +/- 0.19(syst.) pb. From this cross-section, the W mass is derived within the framew…

Search for contact interactions in the reactionse + e −→l + l − ande + e −→γγ

1993

Contact interactions are searched for using the differential cross sections for the reactions e + e -→ e + e -, e + e -→ µ + µ -, e + e -→ τ + τ - and e + e -→γγ measured at 12 energies around the Z peak and corresponding to about 20 pb-1 of cumulated luminosity. Four-fermion contact term models assuming various chiralities of lepton currents are fitted to the lepton data and lower limits on the energy scale Λ of such terms are set at 95% c.l. The limits vary in the range 0.9 4.7 TeV, depending on the model and on the lepton flavour. The eeγγ contact terms are searched for assuming various chiralities. Limits on the energy scale Λ between 79 and 130 GeV are extracted from the data. The resu…

Transverse momentum correlations in hadronic Z decays

1997

Using data obtained with the ALEPH detector at the Z resonance, a measure based on transverse momentum is shown to exhibit a correlation between the two halves of a hadronic event which cannot be explained by energy-momentum conservation, flavour conservation, the imposition of an event axis or imperfect event reconstruction. Two possible interpretations based on existing Monte Carlo models are examined: a) ARIADNE, with the correlation forming early in the parton shower and with the transition from partons to hadrons playing only a minor part; b) JETSET, with the correlation forming at the fragmentation stage. A correlation technique based on a jet cluster analysis is used to make a compar…

Scalar quark searches in $e^+ e^-$ collisions at $\sqrt{s}$ = 181-184 GeV

1998

Searches for scalar top, scalar bottom and degenerate scalar quarks have been performed with data collected with the ALEPH detector at LEP. The data sample consists of 57 pb^-1 taken at sqrt{s} = 181-184 GeV. No evidence for scalar top, scalar bottom or degenerate scalar quarks was found in the channels tilde{t} --> c chi, tilde{t} --> b l snu, tilde{b} --> b chi, and tilde{q} --> q chi. From the channel tilde{t} --> c chi a limit of 74 GeV/c^2 has been set on the scalar top quark mass, independent of the mixing angle. This limit assumes a mass difference between the stop and the chi in the range 10-40 GeV/c^2. From the channel tilde{t} --> b l snu the mixing-angle-indepen…

Observation of D0→K1(1270)−e+νe

2021

Using 2.93 fb^{-1} of e^{+}e^{-} collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D^{0}→K_{1}(1270)^{-}e^{+}ν_{e} semileptonic decay is presented. The statistical significance of the decay D^{0}→K_{1}(1270)^{-}e^{+}ν_{e} is greater than 10σ. The branching fraction of D^{0}→K_{1}(1270)^{-}e^{+}ν_{e} is measured to be (1.09±0.13_{-0.16}^{+0.09}±0.12)×10^{-3}. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K_{1}(1270)^{-}→K^{-}π^{+}π^{-}. The fraction of longitudinal polarization in D^{0}→K_{1}(1270)^{-}e^{+}ν_{e} is determined for the first time t…

Measurement of cross sections of the interactions e+e−→ ϕϕω and e+e−→ ϕϕϕ at center-of-mass energies from 4.008 to 4.600 GeV

2017

Abstract Using data samples collected with the BESIII detector at the BEPCII collider at six center-of-mass energies between 4.008 and 4.600 GeV, we observe the processes e + e − → ϕ ϕ ω and e + e − → ϕ ϕ ϕ . The Born cross sections are measured and the ratio of the cross sections σ ( e + e − → ϕ ϕ ω ) / σ ( e + e − → ϕ ϕ ϕ ) is estimated to be 1.75 ± 0.22 ± 0.19 averaged over six energy points, where the first uncertainty is statistical and the second is systematic. The results represent first measurements of these interactions.

Observation of a Near-Threshold Structure in the K+ Recoil-Mass Spectra in e+e−→K+(Ds−D*0+Ds*−D0)

2021

We report a study of the processes of e^{+}e^{-}→K^{+}D_{s}^{-}D^{*0} and K^{+}D_{s}^{*-}D^{0} based on e^{+}e^{-} annihilation samples collected with the BESIII detector operating at BEPCII at five center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7  fb^{-1}. An excess of events over the known contributions of the conventional charmed mesons is observed near the D_{s}^{-}D^{*0} and D_{s}^{*-}D^{0} mass thresholds in the K^{+} recoil-mass spectrum for events collected at sqrt[s]=4.681  GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5_{-2.6}^{+1.8}±2.1)  MeV/c^{2} and (…

Search for neutral Higgs bosons from supersymmetry in Z decays

1990

The light scalar Higgs boson h and the pseudoscalar Higgs boson A of the minimal supersymmetric standard model have been searched for in the processes e+e−→hff and e+e−→hA using data collected by ALEPH at the LEP e+e− collider, with center of mass energies at and near the Z peak. Using a variety of signatures adapted to various mass ranges for h and A, we have excluded a large domain in the parameter space. For large values of ν2ν1, the ratio of the vacuum expectation values of the two Higgs fields, the whole range from 0 to 38.8 GeV is excluded for Mh and MA at 95% CL.

Study ofD+→K−π+e+νe

2016

We present an analysis of the decay D+ -> K-pi(+)e(+)nu(e) based on data collected by the BESIII experiment at the psi(3770) resonance. Using a nearly background-free sample of 18262 events, we measure the branching fraction B(D+ -> K-pi+e+nu e) = (3.77 +/- 0.03 +/- 0.08)%. For 0.8 K-pi+e+nu e)([0.8,1.0]) = (3.39 +/- 0.03 +/- 0.08)%. A partial wave analysis shows that the dominant (K) over bar* (892)degrees component is accompanied by an S-wave contribution accounting for (6.05 +/- 0.22 +/- 0.18)% of the total rate and that other components are negligible. The parameters of the (K) over bar* (892)degrees resonance and of the form factors based on the spectroscopic pole dominance predictions…

Measurements of Absolute Branching Fractions of Fourteen Exclusive Hadronic D Decays to η

2020

Using 2.93 fb(-1) of e(+)e(-) collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the absolute branching fractions of 14 hadro ...

Measurement of the Branching Fraction For the Semileptonic Decay D0(+)→π−(0)μ+νμ and Test of Lepton Flavor Universality

2018

Using a data sample corresponding to an integrated luminosity of 2.93 fb(-1) taken at a center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we perform an analysis of the semileptonic decays D0(+) -> pi(-(0))mu(+)nu(mu ). The branching fractions of D-0 -> pi(-)mu(+)nu(mu), and D+ -> pi(0)mu(+)nu(mu ) are measured to be (0.272 +/- 0.008(start) +/- 0.006(syst))% and (0.350 +/- 0.011(star) +/- 0.010(syst))%, respectively, where the former is of much improved precision compared to previous results and the latter is determined for the first time. Using these results along with previous BESIII measurements of D0(+) -> pi(-(0))e(+)nu(e), we calculate the bra…

Search for new decay modes of the ψ2(3823) and the process e+e−→π0π0ψ2(3823)

2021

The decays ψ2(3823)→γχc0,1,2, π+π−J/ψ, π0π0J/ψ, ηJ/ψ, and π0J/ψ are searched for using the reaction e+e−→π+π−ψ2(3823) in a 19  fb−1 data sample collected at center-of-mass energies between 4.1 and ...

Search for charginos and neutralinos with R-parity violation at =130 136

1996

Searches for charginos and neutralinos produced in e+e− collisions at centre-of-mass energies of 130 and 136 GeV have been performed under the assumptions that R-parity is not conserved, that the dominant R-parity violating coupling involves only leptonic fields, and that the lifetime of the lightest supersymmetric particle can be neglected. In the 5.7 pb−1 data sample collected by ALEPH, no candidate events were found. As a result, chargino and neutralino masses and couplings are constrained and the domains previously excluded at LEP1 are extended.

Measurement of the b → τ-ν̄τX branching ratio

1993

The definitions of “anthropology” found in various dictionaries cover a whole range of terms and in this section we provide an overview of all its connotations. In this way a variety of reflections about the essence of man become possible, for instance as : summit of creation; source of his own values; specific biological reality; intelligence (but what is this, really?); knowing subject or object of knowledge; social being and product of a culture. Following these lines of thought one realises that all these preoccupations have already been taken up, or at least touched upon, by communication theory.

Observation of the rare η→e+e−e+e− decay with the KLOE experiment

2011

Abstract We report the first observation of the rare η → e + e − e + e − ( γ ) decay based on 1.7 fb − 1 collected by the KLOE experiment at the DAΦNE ϕ-factory. The selection of the e + e − e + e − final state is fully inclusive of radiation. We have identified 362 ± 29 events resulting in a branching ratio of ( 2.4 ± 0.2 stat + bckg ± 0.1 syst ) × 10 − 5 .

Searches for the standard Higgs boson

1990

Abstract A data sample corresponding to about 100 000 hadronic Z decays collected by ALEPH at LEP has been used to search for the standard Higgs boson produced in the reaction e + e − → H 0 Z 0∗ . No indication for any signal was found, and a 95% CL lower limit on the Higgs boson mass has been set at 41.6 GeV.

Measurement of the absolute branching fraction of D + → K̅ 0 e + ν e via K̅ 0 → π 0 π 0

2016

By analyzing 2.93 fb(-1) data collected at the center-of-mass energy root s = 3.773 GeV with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay D+ -> (K) over bar (0)e(+)nu(e) to be B(D (+) -> (K) over bar (0)e(+)nu(e)) = (8.59 +/- 0.14 +/- 0.21)% using (K) over bar (0) -> K-S(0) -> pi(0) pi(0), where the first uncertainty is statistical and the second systematic. Our result is consistent with previous measurements within uncertainties..

Evidence of Two Resonant Structures in e+e−→π+π−hc

2017

The cross sections of e(+)e(-) -> pi(+) pi(-) hc at center-of-mass energies from 3.896 to 4.600 GeVare measured using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of e(+)e(-) -> pi(+) pi(-) J/psi and e(+)e(-) -> pi(+) pi(-) psi (2S), but the line shape is inconsistent with the Y states observed in the latter two modes. Two structures are observed in the e(+)e(-) -> pi(+) pi(-) hc cross sections around 4.22 and 4.39 GeV/c(2), which we call Y(4220)and Y(4390), respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of (4218.4(- 4.5)…

Search for high mass photon pairs in (f= e, μ, τ, v, q) at LEP

1993

Abstract The result of a search for high mass photon pairs from the processes e + e − → f f γγ (f = e, μ, τ, v and q) with the ALEPH detector is reported. The result for f = e , μ and τ is to be compared with the observation of 4 events by the L3 Collaboration with invariant masses, M γγ , of the two photons near 60 GeV. From a data sample approximately twice as large taken from 1990 to 1992, 6 events are found with M γγ distributed between 50 GeV and 72 GeV, while 4.9 events are expected from a QED calculation. There is no evidence for a mass peak; only one event ( μ + μ − γγ ) at M γγ = 59.4 ± 0.2 GeV is compatible with the L3 observation. In addition, for M γγ > 50 GeV, no event is found…

Study of muon-pair production at centre-of-mass energies from 20 to 136 GeV with the ALEPH detector

1997

The total cross section and the forward-backward asymmetry for the process e(+)e --> mu(+)mu(-)(n gamma) are measured in the energy range 20-136 GeV by reconstructing the effective centre-of-mass energy after initial state radiation. The analysis is based on the data recorded with the ALEPH detector at LEP between 1990 and 1995, corresponding to a total integrated luminosity of 143.5 pb(-1). Two different approaches are used: in the first one an exclusive selection of events with hard initial state radiation in the energy range 20-88 GeV is directly compared with the Standard Model predictions showing good agreement. In the second one, all events are used to obtain a precise measurement of …

Studies of QCD in ${\rm e^+ e^-}\to $ hadrons at $E_{\rm cm} = 130$ and 136 GeV

1997

Studies of QCD in $\mbox{e}^+\mbox{e}^- \rightarrow$ Hadrons at $E_{cm} = $} 130 and 136 GeV The ALEPH Collaboration An analysis of the properties of hadronic final states produced in electron-positron annihilation at centre-of-mass energies of 130 and 136 GeV is presented. The measurements are based on a data sample of 5.7 $\mbox{pb}^{-1}$ collected in November 1995 with the \Aleph detector at LEP. Inclusive charged particle distributions, jet rates and event-shape distributions are measured and the results are compared with the predictions of QCD-based models. From the measured distributions quantities are determined for which the dependence on the centre-of-mass energy can be predicted b…

Resonant structure and flavour tagging in the Bπ±system using fully reconstructed B decays

1998

Abstract Starting from a sample of four million hadronic Z decays collected with the ALEPH detector at LEP, 404 charged and neutral B mesons are fully reconstructed and used to look for resonant structure in the Bπ system. An excess of events is observed above the expected background in the Bπ mass spectrum at a mass ≈5.7 GeV/c 2 , consistent with the production and decay to B (∗) π of the B ∗∗ states predicted by Heavy Quark Symmetry (HQS). In the framework of HQS, it is found that the mass of the B 2 ∗ state is (5739 + 8 −11 ( stat ) +6 −4 ( syst )) MeV/c 2 and the relative production rate of the B ∗∗ system is BR(b→B ∗∗ →B (∗) π)/BR(b→B u,d )=(31±9 (stat) +6 −5 (syst)) % . In the same sa…

Measurements of Born cross sections of e+e−→Ds*+DsJ−+c.c.

2021

The Born cross sections are measured for the first time for the processes $e^+e^-\to D_s^{*+}D_{s0}^*(2317)^- +c.c.$ and $e^+e^-\to D_s^{*+}D_{s1}(2460)^- +c.c.$ at the center-of-mass energy $\sqrt{s}=$ 4.600~GeV, 4.612~GeV, 4.626~GeV, 4.640~GeV, 4.660~GeV, 4.68~GeV, and 4.700~GeV, and for $e^+e^-\to D_s^{*+}D_{s1}(2536)^- +c.c.$ at $\sqrt{s}=$ 4.660~GeV, 4.680~GeV, and 4.700~GeV, using data samples collected with the BESIII detector at the BEPCII collider. No structures are observed in cross-section distributions for any of the processes.

Determination of the Pseudoscalar Decay Constant fDs+ via Ds+→μ+νμ

2020

Search for a new weakly interacting particle

1991

Abstract A search for events of the type e + e − →l + l − X 0 , where X 0 can be any weakly interacting particle which couples to the Z, has been performed with the ALEPH detector at LEP, by searching for acollinear lepton pairs. Such particles can be excluded up to a mass of 7.0 GeV/c 2 for a value of the ratio of branching fractions, Br( Z →X 0 l + l − )/Br(Z→ l + l − ), greater than 2.5 × 10 −3 if the X 0 has third component of isospin, I 3 greater than 1 2 and decays to a pair of virtual gauge bosons. When this analysis is combined with the previous results of the Higgs particle searches from ALEPH, this limit can be extended to an X 0 mass of 60 GeV/c 2 .

Observation of Λc+→nKS0π+

2017

We report the first direct measurement of decays of the Lambda(+)(c) baryon involving the neutron. The analysis is performed using 567 pb(-1) of e(+)e(-) collision data collected at root s = 4.599 GeV with the BESIII detector at the BEPCII collider. We observe the decay Lambda(+)(c) -> nK(S)(0)pi(+) and measure the absolute branching fraction to be B(Lambda(+)(c) -> nK(S)(0)pi(+)) = [1.82 +/- 0.23(stat) +/- 0.11(syst)]%. A comparison to B[Lambda(+)(c) -> p( (K) over bar pi)(0)] provides an important test of isospin symmetry and final state interactions.

Measurements of the branching fractions of ψ(3686)→Σ¯0Λ+c.c. and χcJ(J=0,1,2)→ΛΛ¯

2021

First Observation of D+→ημ+νμ and Measurement of Its Decay Dynamics

2020

By analyzing a data sample corresponding to an integrated luminosity of 2.93  fb^{-1} collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure for the first time the absolute branching fraction of the D^{+}→ημ^{+}ν_{μ} decay to be B_{D^{+}→ημ^{+}ν_{μ}}=(10.4±1.0_{stat}±0.5_{syst})×10^{-4}. Using the world averaged value of B_{D^{+}→ηe^{+}ν_{e}}, the ratio of the two branching fractions is determined to be B_{D^{+}→ημ^{+}ν_{μ}}/B_{D^{+}→ηe^{+}ν_{e}}=0.91±0.13_{(stat+syst)}, which agrees with the theoretical expectation of lepton flavor universality within uncertainty. By studying the differential decay rates in five four-momentum transfer intervals, we obtain th…

Inclusive production of neutral vector mesons in hadronic Z decays

1996

Data on the inclusive production of the neutral vector mesons rho(0)(770), omega(782), K*(0)(892), and phi (1020) in hadronic Z decays recorded with the ALEPH detector at LEP are presented and compared to Monte Carlo model predictions. Bose-Einstein effects are found to be important in extracting a reliable value for the p(0) production rate. An average p(0) multiplicity of 1.45 +/- 0.21 per event is obtained. The omega is detected via its three pion decay mode omega --> pi(+)pi(-)pi(0) and has a total rate of 1.07 +/- 0.14 per event. The multiplicity of the K*(0) is 0.83 +/- 0.09, whilst that of the phi is 0.122 +/- 0.009, both measured using their charged decay modes. The measurements pro…

Four-fermion production in $e^+e^-$ collisions at centre-of-mass energies of 130 and 136 GeV

1996

Four-fermion events have been selected in a data sample of 5.8 pb(-1) collected with the ALEPH detector at centre-of-mass energies of 130 and 136 GeV. The final states l(+)l(-), l(+)l(-)l(+)l(-), , and <l(+)l(-) have been examined Five events are observed in the data, in agreement with the Standard Model predictions of 6.67 +/- 0.38 events from four-fermion processes and 0.14(-0.05)(+0.19) from background processes. RI ANTONELLI, ANTONELLA/C-6238-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; Sanchez, Federico/F-5809-2012; Ferrante, Isidoro/F-1017-2012

A measurement of Rb using a lifetime-mass tag

1997

ALEPH's published measurement of R-b = Gamma(Z --> b (b) over bar)/Gamma(Z --> hadrons) using a lifetime tag is updated using the full LEP 1 data sample. Considerable effort has been devoted to understanding systematic effects. Charm background is better controlled by combining the lifetime tag with a tag based on the b/c hadron mass difference. Furthermore, the algorithm used to reconstruct the event primary vertex is designed so as to reduce correlations between the two hemispheres of an event. The value of R-b is measured to be 0.2167 +/- 0.0011(stat) +/- 0.0013(syst). (C) 1997 Published by Elsevier Science B.V. RI ANTONELLI, ANTONELLA/C-6238-2011; Passalacqua, Luca/F-5127-2011; Murtas, …

Observation of e+e−→ηhc at center-of-mass energies from 4.085 to 4.600 GeV

2017

We observe for the first time the process e(+) e(-) -> eta h(c) with data collected by the BESIII experiment. Significant signals are observed at the center-of-mass energy root s = 4.226 GeV, and the Born cross section is measured to be (9.5(-2.0)(+2.2)) pb. Evidence for eta h(c) is observed at root s = 4.358 GeV with a Born cross section of (10.0(-2.7)(+3.1)) pb, and upper limits on the production cross section at other center-of-mass energies between 4.085 and 4.600 GeV are determined.

Search for excited leptons in Z0 decay

1990

Due to the severity of system-wide power outages, though their probability of occurrence is slight, regulatory authorities require that a system restoration plan be drawn up and kept up to date at all times. The power outage that affected northeastern North America in 2003 proved the need for such a requirement. The particular structure of Hydro-Quebec's power system requires the use of a highly specific system restoration procedure. The daily preparation of the system restoration plan is based on a strategy whose application requires that a restoration sequence be drawn up that uses available equipment, the electrical behavior of which has been validated using appropriate studies. Over the…

Measurements of the charged particle multiplicity distribution in restricted rapidity intervals

1995

Charged particle multiplicity distributions have been measured with the ALFPH detector in restricted rapidity intervals \Y\ less than or equal to 0.5, 1.0, 1.5, 2.0 along the thrust axis and also without restriction on rapidity. The distribution for the full range can be parametrized by a log-normal distribution. For smaller windows one finds a more complicated structure, which is understood to arise from perturbative effects. The negative-binomial distribution fails to describe the data both with and without the restriction on rapidity. The JETSET model is found to describe all aspects of the data while the width predicted by HERWIG is in significant disagreement.

Study of e+e−→γωJ/ψ and Observation of X(3872)→ωJ/ψ

2019

We study the e^{+}e^{-}→γωJ/ψ process using 11.6  fb^{-1} e^{+}e^{-} annihilation data taken at center-of-mass energies from sqrt[s]=4.008  GeV to 4.600 GeV with the BESIII detector at the BEPCII storage ring. The X(3872) resonance is observed for the first time in the ωJ/ψ system with a significance of more than 5σ. The relative decay ratio of X(3872)→ωJ/ψ and π^{+}π^{-}J/ψ is measured to be R=1.6_{-0.3}^{+0.4}±0.2, where the first uncertainty is statistical and the second systematic (the same hereafter). The sqrt[s]-dependent cross section of e^{+}e^{-}→γX(3872) is also measured and investigated, and it can be described by a single Breit-Wigner resonance, referred to as the Y(4200), with …

Determination of the Spin and Parity of the Zc(3900)

2017

The spin and parity of the Z(c)(3900)(+/-) state are determined to be J(P) = 1(+) with a statistical significance larger than 7 sigma over other quantum numbers in a partial wave analysis of the process e(+)e(-) -> pi(+)pi(-) J/psi We use a data sample of 1.92 fb(-1) accumulated at root s = 4.23 and 4.26 GeV with the BESIII experiment. When parametrizing the Z(c)(3900)(+/-) with a Flatte-like formula, we determine its pole mass M-pole = (3881.2 +/- 4.2(stat) +/- 52.7(syst)) MeV/c(2) and pole width Gamma(pole) = (51.8 +/- 4.6(stat) +/- 36.0(syst)) MeV. We also measure cross sections for the process e(+)e(-) -> Z(c)(3900)(+)pi(-) + c.c. -> J/psi pi(+)pi(-) and determine an upper limit at the …

First measurement of e+e−→pKS0n¯K−+c.c. above open charm threshold

2018

The process e(+)e(-) -> pK(S)(0)(n) over barK(-) + c.c. and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-o ...

Measurement of the e+e− → π+π− cross section between 600 and 900 MeV using initial state radiation

2020

Measurement of the ratio using event shape variables

1993

Abstract The branching fraction of Z → b b relative to all hadronic decays of the Z has been measured using event shape variables to preferentially select Z → b b events. The method chosen applies a combination of shape discriminators and the selection of high transverse momentum leptons to event hemispheres. From a sample of 440 000 hadronic Z decays collected with the ALEPH detector at LEP, the ration Γ b b Γ had = 0.228±0.005( stat. )±0.005( syst. ) is measured.

Precision Study of η′→γπ+π− Decay Dynamics

2018

Using a low background data sample of 9.7×10^{5}  J/ψ→γη^{'}, η^{'}→γπ^{+}π^{-} events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the BESIII detector at BEPCII, the decay dynamics of η^{'}→γπ^{+}π^{-} are studied with both model-dependent and model-independent approaches. The contributions of ω and the ρ(770)-ω interference are observed for the first time in the decays η^{'}→γπ^{+}π^{-} in both approaches. Additionally, a contribution from the box anomaly or the ρ(1450) resonance is required in the model-dependent approach, while the process specific part of the decay amplitude is determined in the model-independent approach.

Study of D0– mixing and D0 doubly Cabibbo-suppressed decays

1998

Abstract Using a sample of four million hadronic Z events collected in ALEPH from 1991 to 1995, the decays D ∗+ → D 0 π s + , with D0 decaying to K−π+ or to K+π−, are studied. The relative branching ratio B(D0→K+π−)/B(D0→K−π+) is measured to be 1.84±0.59( stat. ) ±0.34( syst. ) %. The two possible contributions to the D0→K+π− decay, doubly Cabibbo-suppressed decays and D0– D 0 mixing, are disentangled by measuring the proper-time distribution of the reconstructed D0's. Assuming no interference between the two processes, the upper limit obtained on the mixing rate is 0.92% at 95% CL . The possible effect of interference between the two amplitudes is also assessed.

Measurement of the Absolute Branching Fraction of Ds+→τ+ντ via τ+→e+νeν¯τ

2021

Using a dataset of 6.32  fb^{-1} of e^{+}e^{-} annihilation data collected with the BESIII detector at center-of-mass energies between 4178 and 4226 MeV, we have measured the absolute branching fraction of the leptonic decay D_{s}^{+}→τ^{+}ν_{τ} via τ^{+}→e^{+}ν_{e}ν[over ¯]_{τ}, and find B_{D_{s}^{+}→τ^{+}ν_{τ}}=(5.27±0.10±0.12)×10^{-2}, where the first uncertainty is statistical and the second is systematic. The precision is improved by a factor of 2 compared to the previous best measurement. Combining with f_{D_{s}^{+}} from lattice quantum chromodynamics calculations or the |V_{cs}| from the CKMfitter group, we extract |V_{cs}|=0.978±0.009±0.012 and f_{D_{s}^{+}}=(251.1±2.4±3.0)  MeV, r…

Measurements of Sigma(+) and Sigma(-) time-like electromagnetic form factors for center-of-mass energies from 2.3864 to 3.0200 GeV

2021

Physics letters / B 814, 136110 (2021). doi:10.1016/j.physletb.2021.136110

Charm counting in b decays

1996

??? The inclusive production of charmed particles in Z--> decays has been measured from the yield of D-0, D+, D-s(+) and Lambda(c)(+) decays in a sample of events with high b purity collected with the ALEPH detector from 1992 to 1995. From these measurements, adding the charmonia production rate and an estimate of the charmed strange baryon contribution, the average number of charm quarks per b decay is determined to be n(c)=1.230+/-0.036+/-0.038+/-0.053, where the uncertainties are due to statistics, systematic effects and branching ratios, respectively.

Search for supersymmetric particles using acoplanar charged-particle pairs from Z0 decays

1990

We have performed a search for supersymmetric particles using acoplanar pairs of oppositely-charged particles in decays of the Z0. In 0.53 pb−1 of integrated luminosity near the Z0 peak, we observe two events where approximately four are expected from background, allowing limits to be extended on combined photino and slepton masses, and also on combined photino and chargino masses.

Evidence for e+e−→γηc(1S) at center-of-mass energies between 4.01 and 4.60 GeV

2017

We present first evidence for the process e(+)e(-) -> gamma eta(c)(1S) at six center-of-mass energies between 4.01 and 4.60 GeV using data collected by the BESIII experiment operating at BEPCII. We measure the Born cross section at each energy using a combination of twelve eta(c)(1S) decay channels. We also combine all six energies under various assumptions for the energy-dependence of the cross section. If the process is assumed to proceed via the Y(4260), we measure a peak Born cross section sigma(peak)(e(+)e(-) -> gamma eta(c)(1S)) = 2.11 +/- 0.49 (stat.) +/- 0.36 (syst.) pb with a statistical significance of 4.2 sigma.

Test of the flavour independence of αs

1995

Abstract Using about 950000 hadronic events collected during 1991 and 1992 with the ALEPH detector, the ratios r b = α s b α s udsc and r uds = α s uds α s cb have been measured in order to test the flavour independence of the strong coupling constant α s . The analysis is based on event-shape variables using the full hadronic sample, two b -quark samples enriched by lepton tagging and lifetime tagging, and a light-quark sample enriched by lifetime antitagging. The combined results are r b = 1.002±0.023 and r uds = 0.971 ± 0.023.

Measurement of the inclusive branching fraction for ψ(3686)→KS0+anything

2021

Abstract Using 5.9 pb−1 of e + e − annihilation data collected at center-of-mass energies from 3.640 to 3.701 GeV with the BESIII detector at the BEPCII Collider, we measure the observed cross sections of e + e − → K S 0 X (where X = anything ). From a fit to these observed cross sections with the sum of continuum and ψ ( 3686 ) and J / ψ Breit-Wigner functions and considering initial state radiation and the BEPCII beam energy spread, we obtain for the first time the product of ψ ( 3686 ) leptonic width and inclusive decay branching fraction Γ ψ ( 3686 ) e e B ( ψ ( 3686 ) → K S 0 X ) = ( 373.8 ± 6.7 ± 20.0 ) eV, and assuming Γ ψ ( 3686 ) e e is ( 2.33 ± 0.04 ) keV from PDG value, we measur…

Search for the neutral Higgs bosons of the MSSM in e(+)e(-) collisions at root s from 130 to 172 GeV

1997

The process e(+)e(-) --> hA is used to search for the Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM), in the b (b) over bar b (b) over bar and tau(+)tau(-)b (b) over bar final states, The search is performed in the data collected by the ALEPH experiment at LEP, at centre-of-mass energies between 130 and 172 GeV and with a total luminosity of 27.2 pb(-1). No candidate events are found in either of the final states, in agreement with the expected background of 0.91 events from all Standard Model processes. Combined with searches for e(+)e(-) --> hZ, this results in a 95% C.L. lower limit on the masses of both h and A of 62.5 GeV/c(2), for tan beta > 1. (C) 1997 Elsevier Scie…

Measurement of the absolute branching fractions of J/ψ→γη and η decay modes

2021

Study of BESIII trigger efficiencies with the 2018 J/psi data

2021

Using a dedicated data sample taken in 2018 on the $J/\psi$ peak, we perform a detailed study of the trigger efficiencies of the BESIII detector. The efficiencies are determined from three representative physics processes, namely Bhabha-scattering, dimuon production and generic hadronic events with charged particles. The combined efficiency of all active triggers approaches $100\%$ in most cases with uncertainties small enough as not to affect most physics analyses.

Measurement of higher-order multipole amplitudes in ψ(3686)→γχc1,2 with χc1,2→γJ/ψ and search for the transition ηc(2S)→γJ/ψ

2017

Using 106 x 10(6) psi(3686) events collected with the BESIII detector, we measure multipole amplitudes for the decay psi(3686) ->; gamma chi(c1,2) -> gamma gamma J/psi beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole (M2) amplitude for psi(3686) -> gamma chi(c1,2) -> gamma gamma J/psi and the normalized electric-dipole amplitudes for psi(3686) -> gamma chi(c2) -> gamma J/psi and determined. The M2 amplitudes for psi(3686) -> gamma chi(c1) and ; chi(c1,2) -> gamma J/psi are found to differ significantly from zero and are consistent with theoretical predictions. We also obtain the ratios of M2 contributions of psi(3686) and J/psi decays to;2,chi(c1,2,) b(2)(1…

Observation of the Semileptonic D+ Decay into the K¯1(1270)0 Axial-Vector Meson

2019

By analyzing a 2.93 fb(-1) data sample of e(+)e(-) collisions, recorded at a center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we report the first observa ...

Measurement of the branching fraction for D0 → K-π+

1997

The branching fraction for D-0 --> K(-)pi(+) is measured with the statistics collected by ALEPH from 1991 to 1994. The method is based on the comparison between the rate for the reconstructed D*+ --> (D) pi(+), D-0 --> K(-)pi(+) decay chain and the rate for inclusive soft pion production at low transverse momentum with respect to the nearest jet. The result is B(D-0 --> K(-)pi(+)) = (3.90 +/- 0.09 +/- 0.12)% (C) 1997 Published by Elsevier Science B.V. RI ANTONELLI, ANTONELLA/C-6238-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; St.Denis, Richard/C-8997-2012; Sanchez, Federico/F-5809-2012; Forti, Francesco/H-3035-2011; Ferrante, Isidoro/F-1017-2012

Search for a non-minimal Higgs boson produced in the reaction →

1993

Abstract A data sample corresponding to 1.23 million hadronic Z decays collected by the ALEPH detector at LEP has been searched for signals of the production of a non-minimal CP-even Higgs boson h in the reaction e + e − → hZ ∗ . The h decay modes considered were: those of the minimal standard model Higgs boson, with modified branching ratios; decays into a pair of CP-odd Higgs bosons A; and decays into invisible final states. Only one event was found, a very acoplanar e+e− pair which could originate from the standard model background process e + e − → e + e − v v . Upper limits for the cross-section of the reaction e + e − → hZ ∗ have been derived as a function of mh, the mass of the Higgs…

First measurement of the quark-to-photon fragmentation function

1996

Earlier measurements at LEP of isolated hard photons in hadronic Z decays, attributed to radiation from primary quark pairs, have been extended in the ALEPH experiment to include hard photon production inside hadron jets. Events are selected where all particles combine democratically to form hadron jets, one of which contains a photon with a fractional energy z greater than or equal to 0.7. After statistical subtraction of non-prompt photons, the quark-to-photon fragmentation function, D(z), is extracted directly from the measured 2-jet rate. By taking into account the perturbative contributions to D(z) obtained from an O(alpha alpha(s)) QCD calculation, the unknown non-perturbative compone…

Σ+ and Σ¯− Polarization in the J/ψ and ψ(3686) Decays

2020

From 1310.6 x 10(6) J/psi and 448.1 x 10(6) psi (3686) events collected with the BESIII experiment, we report the first observation of Sigma(+) and (Sigma) over bar (-) spin polarization in e(+)e(- ...

Production of orbitally excited charm mesons in semileptonic B decays

1997

A sample of 3.6 million hadronic Z decays recorded between 1991 and 1995 with the ALEPH detector at LEP is used to investigate semileptonic decays of B mesons into final states involving orbitally excited charm mesons. Topological vertex criteria are used to search for decays involving narrow D** states as well as wide D** resonances and non-resonant D(*)pi final states. The sum of the branching ratios for these processes is measured to be Br((B) over bar --> D pi l(-)(v) over bar) + Br((B) over bar --> D*pi l(-)(v) over bar) = (2.26 +/-t 0.29(stat) +/- 0.33(syst))%, which accounts for a significant fraction of the deficit between inclusive measurements and the sum of exclusive semileptonic…

Measurement of branching fractions for D meson decaying into $ϕ$ meson and a pseudoscalar meson

2019

The four decay modes D0→ϕπ0, D0→ϕη, D+→ϕπ+, and D+→ϕK+ are studied by using a data sample taken at the centre-of-mass energy s=3.773 GeV with the BESIII detector, corresponding to an integrated luminosity of 2.93 fb$^{−1}$. The branching fractions of the first three decay modes are measured to be B(D0→ϕπ0)=(1.168±0.028±0.028)×10−3, B(D0→ϕη)=(1.81±0.46±0.06)×10−4, and B(D+→ϕπ+)=(5.70±0.05±0.13)×10−3, respectively, where the first uncertainties are statistical and the second are systematic. In addition, the upper limit of the branching fraction for D+→ϕK+ is given to be 2.1×10−5 at the 90% confidence level. The ratio of B(D0→ϕπ0) to B(D+→ϕπ+) is calculated to be (20.49±0.50±0.45)%, which is c…

Direct Measurement of the Branching Fractions B(ψ(3686)→J/ψX) and B(ψ(3770)→J/ψX) , and Observation of the State R(3760) in e+e−→J/ψX

2021

We report a measurement of the observed cross sections of e + e - → J / ψ X based on 3.21 fb - 1 of data accumulated at energies from 3.645 to 3.891 GeV with the BESIII detector operated at the BEPCII collider. In analysis of the cross sections, we measured the decay branching fractions of B ( ψ ( 3686 ) → J / ψ X ) = ( 64.4 ± 0.6 ± 1.6 ) % and B ( ψ ( 3770 ) → J / ψ X ) = ( 0.5 ± 0.2 ± 0.1 ) % for the first time. The energy-dependent line shape of these cross sections cannot be well described by two Breit-Wigner (BW) amplitudes of the expected decays ψ ( 3686 ) → J / ψ X and ψ ( 3770 ) → J / ψ X . Instead, it can be better described with one more BW amplitude of the decay R ( 3760 ) → J / …

Determination of the Pseudoscalar Decay Constant fDs+ via Ds+→μ+νμ

2019

Using a 3.19  fb^{-1} data sample collected at an e^{+}e^{-} center-of-mass energy of E_{cm}=4.178  GeV with the BESIII detector, we measure the branching fraction of the leptonic decay D_{s}^{+}→μ^{+}ν_{μ} to be B_{D_{s}^{+}→μ^{+}ν_{μ}}=(5.49±0.16_{stat}±0.15_{syst})×10^{-3}. Combining our branching fraction with the masses of the D_{s}^{+} and μ^{+} and the lifetime of the D_{s}^{+}, we determine f_{D_{s}^{+}}|V_{cs}|=246.2±3.6_{stat}±3.5_{syst}  MeV. Using the c→s quark mixing matrix element |V_{cs}| determined from a global standard model fit, we evaluate the D_{s}^{+} decay constant f_{D_{s}^{+}}=252.9±3.7_{stat}±3.6_{syst}  MeV. Alternatively, using the value of f_{D_{s}^{+}} calculat…

Observation of an Anomalous Line Shape of the η′π+π− Mass Spectrum near the pp¯ Mass Threshold in J/ψ→γη′π+π−

2020

Amplitude analysis of the χc1→ηπ+π− decays

2017

Using 448.0 x 10(6) psi(3686) events collected with the BESIII detector, an amplitude analysis is performed for psi(3686) -> gamma chi(c1), chi(c1) ->eta pi(+)pi(-) decays. The most dominant two- body structure observed is a(0)(980)(+/-) pi(-/+); a(0)(980)(+/-) -> eta pi(+/-.) line shape is modeled using a dispersion relation, and a significant nonzero a(0) (980) coupling to the eta'pi channel is measured. We observe chi(c1) -> a(2)(1700)pi production for the first time, with a significance larger than 17 sigma. The production of mesons with exotic quantum numbers, J(PC) = 1(-+), is investigated, and upper limits for the branching fractions chi(c1) -> pi(1)(1400)(+/-)pi(-/+) , chi(c1) -> pi…

Search for the Standard Model Higgs boson in e+e− collisions at =161, 170 172

1997

The reaction e(+)e(-) --> HZ is used to search for the Standard Model Higgs boson, The data sample consists of integrated luminosities of 10.9 pb(-1), 1.1 pb(-1), and 9.5 pb(-1) collected by the ALEPH experiment at LEP during 1996, at centre-of-mass energies of 161, 170 and 172 GeV, respectively. No candidate events were found, in agreement with the expected background of 0.84 events from all Standard Model processes. This search results in a 95% C.L. lower limit on the Higgs boson mass of 69.4 GeV/c(2). When combined with earlier ALEPH searches performed at energies at and around the Z peak, this limit increases to 70.7 GeV/c(2). (C) 1997 Elsevier Science B.V.

Model-Independent Determination of the Spin of the Ω− and Its Polarization Alignment in ψ(3686)→Ω−Ω¯+

2021

We present an analysis of the process $\psi(3686) \to \Omega^- \bar{\Omega}^+$ ($\Omega^-\to K^-\Lambda$, $\bar{\Omega}^+\to K^+\bar{\Lambda}$, $\Lambda\to p\pi^-$, $\bar{\Lambda}\to \bar{p}\pi^+$) based on a data set of $448\times 10^6$ $\psi(3686)$ decays collected with the BESIII detector at the BEPCII electron-positron collider. The helicity amplitudes for the process $\psi(3686) \to \Omega^- \bar{\Omega}^+$ and the decay parameters of the subsequent decay $\Omega^-\to K^-\Lambda$ $(\bar{\Omega}^+\to K^+\bar{\Lambda})$ are measured for the first time by a fit to the angular distribution of the complete decay chain. The branching fraction of $\psi(3686) \to \Omega^- \bar{\Omega}^+$ is me…

Time performance of a triple-GEM detector at high rate

2020

Gaseous detectors are used in high energy physics as trackers or, more generally, as devices for the measurement of the particle position. For this reason, they must provide high spatial resolution and they have to be able to operate in regions of intense radiation, i.e. around the interaction point of collider machines. Among these, Micro Pattern Gaseous Detectors (MPGD) are the latest frontier and allow to overcome many limitations of the pre-existing detectors, such as the radiation tolerance and the rate capability. The gas Electron Multiplier (GEM) is a MPGD that exploits an intense electric field in a reduced amplification region in order to prevent discharges. Several amplification s…

Search for decays of the Z0 into a photon and a pseudoscalar meson

1990

Abstract A search is reported for decays of the Z 0 into π 0 γ , ηγ and η ′ (958) γ in e + e − collisions using data collected during a scan around the Z 0 mass. In order to search for π 0 γ final states, in which the two photons from the π 0 decay are unresolved, the production of pairs of high-energy electromagnetic clusters is studied. The data are compared with the expectations from the pure QED process e + e − → γγ , and a 95% confidence level upper limit on the branching ratio of the Z 0 into π 0 γ of 4.9 × 10 −4 is derived. For η′γ, the decay modes of the mesons that contain two charged particles are largely free from QED background. These modes are used to place upper limits of 4.6 …

Improved measurement of theB 0 andB + meson lifetimes

1996

The lifetimes of the B 0 and B + mesons have been measured with the Aleph detector at LEP, using approximately 3 million hadronic Z decays collected in the period 1991 1994. In the first of three methods, semileptonic decays of B 0 and B + mesons were partially reconstructed by identifying events containing a lepton with an associated D*- orbar D^0 meson. The second method used fully reconstructed B 0 and B + mesons. The third method, used to measure the B 0 lifetime, employed a partial reconstruction technique to identify B 0→ D*- π + X decays. The combined results are begin{gathered} tau _0 = 1.55 ± 0.06 ± 0.03 ps, \ tau _ + = 1.58 ± 0.09 ± 0.03 ps, \ tfrac{{tau _ + }}{{tau _0 }} = 1.03 ±…

Precision Measurement of the Branching Fractions of η′ Decays

2019

PubMed ID: 31050481

Production of excited beauty states in Z decays

1996

A data sample of about 3.0 million hadronicZ decays collected by the ALEPH experiment at LEP in the years 1991 through 1994 is used to make an inclusive selection of B hadron events. In this event sample 4227±140±252B* mesons in the decayB*→Bγ and 1944±108±161B** u,d mesons decaying into a B meson and a charged pion are reconstructed. Here and in the followingB** u,d denotes the eightL=1(bū) and (bd) states and their charge conjugate. For the well establishedB* meson the following quantities are obtained:ΔM=M B*−MB=(45.30±0.35±0.87) MeV/c2 andN B*/(N B+N B*)=(77.1±2.6±7.0)%. The angular distribution of the photons in theB* rest frame is used to measure the relative contribution of longitudi…

Physics with the KLOE-2 experiment at the upgraded DAFNE

2010

Investigation at a $\phi$--factory can shed light on several debated issues in particle physics. We discuss: i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled kaon states, iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and eta/eta$^\prime$ mesons, iv) the contribution to understand the nature of light scalar mesons, and v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We…

Measurement of e+ e- → DD cross sections at the ψ(3770) resonance

2018

Chinese physics / C High energy physics and nuclear physics C 42(8), 083001 (2018). doi:10.1088/1674-1137/42/8/083001

Measurement of the and B− meson lifetimes

1993

Abstract The lifetimes of the B 0 and B − mesons have been measured with the ALEPH detector at LEP. Semileptonic decays of B 0 and B − mesons were partially reconstructed by identifying events containing a lepton with an associated D ∗+ or D 0 meson. The proper time of the B meson was estimated from the measured decay length and the momentum and mass of the D -lepton system. A fit to the proper time of 77 D ∗+ l − and 77 D 0 l − candidates, combined with a constraint on the lifetime ratio ( τ − τ 0 ) arising from the relative rates of observed D ∗+ l − and D 0 l − events, yielded the following lifetimes: τ 0 =1.52 −0.18 +0.20 ( stat. ) −0.13 +0.07 ( syst. ) ps , τ − = 1.47 −0.19 +0.22 ( sta…

Precision Measurement of the e+e−→Λc+Λ¯c− Cross Section Near Threshold

2018

The cross section of the e(+)e(-) -> Lambda(+)(c)(Lambda) over bar (-)(c) process is measured with unprecedented precision using data collected with the BESIII detector at root s = 4574.5, 4580.0, 4590.0 and 4599.5 MeV. The nonzero cross section near the Lambda(+)(c)(Lambda) over bar (-)(c) production threshold is cleared. At center-of-mass energies root s = 4574.5 and 4599.5 MeV, the higher statistics data enable us to measure the Lambda(c) polar angle distributions. From these, the.c electric over magnetic form-factor ratios (vertical bar G(E)/G(M)vertical bar) are measured for the first time. They are found to be 1.14 +/- 0.14 +/- 0.07 and 1.23 +/- 0.05 +/- 0.03, respectively, where the …

The topology dependence of charged particle multiplicities in three-jet events

1997

A study of individual jet and whole-event charged particle multiplicities in three-jet events measured in e(+)e(-) annihilation at the Z reveals a significant topology dependence. Mean jet multiplicities are inadequately described by jet energies; interjet angles must also be specified. Quantitative tests suggest that it is necessary to use transverse-momentum-like scales to describe the data. RI ANTONELLI, ANTONELLA/C-6238-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; St.Denis, Richard/C-8997-2012; Sanchez, Federico/F-5809-2012; Forti, Francesco/H-3035-2011; Ferrante, Isidoro/F-1017-2012

Fast simulation of muons produced at the SHiP experiment using Generative Adversarial Networks

2019

This paper presents a fast approach to simulating muons produced in interactions of the SPS proton beams with the target of the SHiP experiment. The SHiP experiment will be able to search for new long-lived particles produced in a 400~GeV$/c$ SPS proton beam dump and which travel distances between fifty metres and tens of kilometers. The SHiP detector needs to operate under ultra-low background conditions and requires large simulated samples of muon induced background processes. Through the use of Generative Adversarial Networks it is possible to emulate the simulation of the interaction of 400~GeV$/c$ proton beams with the SHiP target, an otherwise computationally intensive process. For th…

Measurement of cross section for e+e−→Ξ0Ξ¯0 near threshold

2021

Abstract Using e + e − collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb−1, we measure the cross sections and effective form factors for the process e + e − → Ξ 0 Ξ ¯ 0 utilizing a single-tag method. A fit to the cross section of e + e − → Ξ 0 Ξ ¯ 0 with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes e + e − → Ξ − Ξ ¯ + and Ξ 0 Ξ ¯ 0 is calculated using recent BESIII measurement and is found to be compatible with expectation from isosp…

Amplitude Analysis of Ds+→π+π0η and First Observation of the W -Annihilation Dominant Decays Ds+→a0(980)+π0 and Ds+→a0(980)0π+

2019

We present the first amplitude analysis of the decay D_{s}^{+}→π^{+}π^{0}η. We use an e^{+}e^{-} collision data sample corresponding to an integrated luminosity of 3.19  fb^{-1} collected with the BESIII detector at a center-of-mass energy of 4.178 GeV. We observe for the first time the W-annihilation dominant decays D_{s}^{+}→a_{0}(980)^{+}π^{0} and D_{s}^{+}→a_{0}(980)^{0}π^{+}. We measure the absolute branching fraction B(D_{s}^{+}→a_{0}(980)^{+(0)}π^{0^{(}+)},a_{0}(980)^{+(0)}→π^{+(0)}η)=(1.46±0.15_{stat}±0.23_{sys})%, which is larger than the branching fractions of other measured pure W-annihilation decays by at least one order of magnitude. In addition, we measure the branching fracti…

Determination of sin^2(theta(eff)(w)) using jet charge measurements in hadronic Z decays

1996

The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing the original quark and antiquark is measured for b (b) over bar and c (c) over bar events in subsamples selected by their long lifetimes or using fast D*'s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation between charges of opposite hemispheres and agrees wi…

Improved measurements of two-photon widths of the χcJ states and helicity analysis for χc2→γγ

2017

Based on 448.1 x 10(6) Psi(3686) events collected with the BESIII detector, the decays Psi(3686) -> gamma chi(cJ), chi(cJ) -> gamma gamma(J = 0, 1, 2) are studied. The decay branching fractions of chi(c0,2) -> gamma gamma are measured to be B(chi(c0) -> gamma gamma) = (1.93 +/- 0.08 +/- 0.05 +/- 0.05) x 10(-4) and B(chi(c2) -> gamma gamma) = (3.10 +/- 0.09 +/- 0.07 +/- 0.11) x 10(-4) which correspond to two-photon decay widths of Gamma(gamma gamma)(chi(c0)) = 2.03 +/- 0.08 +/- 0.06 +/- 0.13 keV and Gamma(gamma gamma)(chi(c2)) = 0.60 +/- 0.02 +/- 0.01 +/- 0.04 keV with a ratio of R = Gamma(gamma gamma)(chi(c2))/Gamma(gamma gamma)(chi(c0)) = 0.295 +/- 0.014 +/- 0.007 +/- 0.027, where the unce…

Measurement of e+e−→γχc0,c1,c2 cross sections at center-of-mass energies between 3.77 and 4.60 GeV

2021

Study of J/ψ and ψ(3686)→Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0

2017

Abstract We study the decays of J / ψ and ψ ( 3686 ) to the final states Σ ( 1385 ) 0 Σ ¯ ( 1385 ) 0 and Ξ 0 Ξ ¯ 0 based on a single baryon tag method using data samples of ( 1310.6 ± 7.0 ) × 10 6 J / ψ and ( 447.9 ± 2.9 ) × 10 6 ψ ( 3686 ) events collected with the BESIII detector at the BEPCII collider. The decays to Σ ( 1385 ) 0 Σ ¯ ( 1385 ) 0 are observed for the first time. The measured branching fractions of J / ψ and ψ ( 3686 ) to Ξ 0 Ξ ¯ 0 are in good agreement with, and much more precise than, the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for J / ψ → Σ ( 1385 ) 0 Σ ¯ ( 1385 ) 0 , …

Search for excited neutrinos in Z decay

1990

Excited neutrinos decaying into a neutrino and a photon are searched for in the ALEPH detector at LEP. No evidence is found for Z decay into vv∗ or v∗v∗ final states. Upper limits are derived on excited neutrino couplings up to excited neutrino masses close to the Z mass. Lower limits on the v∗ mass, independent of the v∗ decay modes, are deduced from the total Z width.

Search for the decay ϕ→K0K¯0γ with the KLOE experiment

2009

Abstract We have searched for the decay ϕ → K 0 K ¯ 0 γ , by detecting K S pairs plus a photon and with the K S -mesons decaying to π + π − , in a sample of about 1.5 × 10 9 ϕ-decays collected by the KLOE experiment at DAΦNE. The reaction proceeds through the intermediate states f 0 ( 980 ) γ , a 0 ( 980 ) γ . We find five events with 3.2 events expected from background processes. We obtain the upper limit: BR ( ϕ → K 0 K ¯ 0 γ ) 1.9 × 10 − 8 at 90% CL.

Observation of a resonant structure in e+e− → ωη and another in e+e− → ωπ0 at center-of-mass energies between 2.00 and 3.08 GeV

2021

Abstract Born cross sections for the processes e + e − → ω η and e + e − → ω π 0 have been determined for center-of-mass energies between 2.00 and 3.08 GeV with the BESIII detector at the BEPCII collider. The results obtained in this work are consistent with previous measurements but with improved precision. Two resonant structures are observed. In the e + e − → ω η cross sections, a resonance with a mass of ( 2176 ± 24 ± 3 ) MeV / c 2 and a width of ( 89 ± 50 ± 5 ) MeV is observed with a significance of 6.2σ. Its properties are consistent with the ϕ ( 2170 ) . In the e + e − → ω π 0 cross sections, a resonance denoted Y ( 2040 ) is observed with a significance of more than 10σ. Its mass an…

Search for the rare semi-leptonic decay J/ψ → D−e+ ν e + c.c.

2021

Abstract Using 10.1 × 109J/ψ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $$ \sqrt{s} $$ s = 3.097 GeV and collected with the BESIII detector, we present a search for the rare semi-leptonic decay J/ψ → D−e+νe + c.c. No excess of signal above background is observed, and an upper limit on the branching fraction ℬ(J/ψ → D−e+νe + c. c.) &lt; 7.1 × 10−8 is obtained at 90% confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.

Study of the D0→K−μ+νμ Dynamics and Test of Lepton Flavor Universality with D0→K−ℓ+νℓ Decays

2019

Using e^{+}e^{-} annihilation data of 2.93  fb^{-1} collected at center-of-mass energy sqrt[s]=3.773  GeV with the BESIII detector, we measure the absolute branching fraction of D^{0}→K^{-}μ^{+}ν_{μ} with significantly improved precision: B_{D^{0}→K^{-}μ^{+}ν_{μ}}=(3.413±0.019_{stat}±0.035_{syst})%. Combining with our previous measurement of B_{D^{0}→K^{-}e^{+}ν_{e}}, the ratio of the two branching fractions is determined to be B_{D^{0}→K^{-}μ^{+}ν_{μ}}/B_{D^{0}→K^{-}e^{+}ν_{e}}=0.974±0.007_{stat}±0.012_{syst}, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. A study of the ratio of the two branching fractions in different four-momentum tra…

Evidence for the singly Cabibbo suppressed decayΛc+→pηand search forΛc+→pπ0

2017

We study the singly Cabibbo suppressed decays Lambda(+)(c) -> p eta and Lambda(+)(c) -> p pi(0) using Lambda(+)(c)(Lambda) over bar (-)(c) pairs produced by e(+)e(-) collisions at a center-of-mass energy of root s = 4.6 GeV. The data sample was collected by the BESIII detector at the BEPCII collider and corresponds to an integrated luminosity of 567 pb(-1). We find the first evidence for the decay Lambda(+)(c) -> p eta with a statistical significance of 4.2 sigma and measure its branching fraction to be B(Lambda(+)(c) -> p eta) = (1.24 +/- 0.28(stat) +/- 0.10(sys)) x 10(-3). No significant Lambda(+)(c) -> p pi(0) signal is observed. We set an upper limit on its branching fraction B(Lambda(+…

Searches for scalar top and scalar bottom quarks at LEP2

1997

Searches for scalar top and bottom quarks have been performed with data collected by the ALEPH detector at LEP. The data sample consists of 21.7 pb^-1 taken at sqrt{s} = 161, 170, and 172~GeV and 5.7 pb^-1 taken at sqrt{s} = 130 and 136~GeV. No evidence for scalar top quarks or scalar bottom quarks was found in the channels stop --&gt; c chi, stop --&gt; b l snu, and sbottom --&gt; b chi. For the channel stop --&gt; c chi a limit of 67 GeV/c^2 has been set on the scalar top quark mass, independent of the mixing angle between the supersymmetric partners of the left and right-handed states of the top quark. This limit assumes a mass difference between the stop and the chi of at least 10 GeV/c…

Observation of the Semileptonic Decay D0→a0(980)−e+νe and Evidence for D+→a0(980)0e+νe

2018

Using an e(+)e(-) collision data sample of 2.93 fb(-1) collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of D-0 -> a(0)(980)(-)e(+)nu( ...

Measurement of the branching ratio and an upper limit on

1995

Abstract Using 1.45 million hadronic Z decays collected by the ALEPH experiment at LEP, the b → τ − ν - τ X branching ratio is measured to be 2.75 ± 0.30 ± 0.37%. In addition an upper limit of 1.8 × 10 −3 at 90% confidence level is placed upon the exclusive branching ratio of B − → τ − ν - τ . These measurements are consistent with SM expectations, and put the constraint tan β M h ± GeV −1 at 90% confidence level on all Type II two Higgs doublet models (such as the MSSM).

Improved measurements of branching fractions for ηc→ϕϕ and ωϕ

2017

Using (223.7 +/- 1.4) x 10(6) J / Psi events accumulated with the BESIII detector, we study eta(c) decays to phi phi and omega phi final states. The branching fraction of n(c) -> phi phi is measured to be Br(eta(c) -> phi phi) = (2.5 +/- 0(-0.7)(+0.3) +/- 0.6) X 10(-3,) where the first uncertainty is statistical, the second is systematic, and the third is from the uncertainty of Br(J / Psi -> gamma eta(C)). No significant signal for the double Okubo-Zweig-Iizuka suppressed decay of eta(c) -> omega phi is observed, and the upper limit on the branching fraction is determined to be Br(eta(c) -> omega phi) < 2.5 x 10(-4) at the 90% confidence level.

Measurement of branching fractions for ψ(3686)→γη′ , γη , and γπ0

2017

Using a data sample of 448 x 10(6) psi(3686) events collected with the BESIII detector operating at the BEPCII storage ring, the decays psi(3686) -> gamma eta and psi(3686) -> gamma pi(0) are observed with a statistical significance of 7.3 sigma and 6.7 sigma, respectively. The branching fractions are measured to be B(psi(3686) -> gamma eta) = (0.85 +/- 0.18 +/- 0.05) x 10(-6) and B(psi(3686) ->gamma pi(0)) = (0.95 +/- 0.16 +/- 0.05) x 10(-6). In addition, we measure the branching fraction of psi(3686) -> gamma eta' to be B(psi(3686) -> gamma eta') = (125.1 +/- 2.2 +/- 6.2)x10(-6), which represents an improvement of precision over previous results.

An improved limit for Γee of X(3872) and Γee measurement of ψ(3686)

2015

Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e(+)e(-) -> gamma(ISR) X(3872) -> gamma(ISR)pi(+ ...

Observation of e + e − → ηψ(2S) at center-of-mass energies from 4.236 to 4.600 GeV

2021

Journal of high energy physics 2021(10), 177 (2021). doi:10.1007/JHEP10(2021)177

Inclusive production of neutral pions in hadronic Z decays

1997

A measurement of the inclusive production of pi(0) mesons in hadronic Z decays is presented and compared to Monte Carlo model predictions. The analysis is based on approximately 2 million hadronic events recorded with the ALEPH detector at LEP at a centre-of-mass energy of root s = 91.2 GeV. Neutral pions are reconstructed using photons measured in the electromagnetic calorimeter and photons from conversion pairs. The inclusive pi(0) momentum spectrum is measured in the range 0.025 < x(p) = p/p(beam) < 1. In this range the number of pi(0) per hadronic Z is found to be 4.80 +/- 0.07(stat) +/- 0.31(sys). The differential inclusive pi(0) cross section is also measured as a function of transver…

Study of the decay D+→K*(892)+KS0 in D+→K+KS0π0

2021

Based on an $e^{+}e^{-}$ collision data sample corresponding to an integrated luminosity of 2.93 $\mathrm{fb}^{-1}$ collected with the BESIII detector at $\sqrt{s}=3.773 \mathrm{GeV}$, the first amplitude analysis of the singly Cabibbo-suppressed decay $D^{+}\to K^+ K_S^0 \pi^0$ is performed. From the amplitude analysis, the $K^*(892)^+ K_S^0$ component is found to be dominant with a fraction of $(57.1\pm2.6\pm4.2)\%$, where the first uncertainty is statistical and the second systematic. In combination with the absolute branching fraction $\mathcal{B}(D^+\to K^+ K_S^0 \pi^0)$ measured by BESIII, we obtain $\mathcal{B}(D^+\to K^*(892)^+ K_S^0)=(8.69\pm0.40\pm0.64\pm0.51)\times10^{-3}$, where…

Observation of the Doubly Cabibbo-Suppressed Decay D+→K+π+π−π0 and Evidence for D+→K+ω

2020

Using 2.93 fb(-1) of e(+)e(-) collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the first observation of the doubly Cabibbo-suppressed decay D+-> K+pi(+) ...

Search for sleptons in e(+)e(-) collisions at centre-of-mass energies up to 184 GeV

1998

The data collected by the ALEPH experiment at LEP at centre-of-mass energies around 183 GeV are analysed to search for sleptons, the partners of leptons in supersymmetric theories. The previously published search for acoplanar leptons and missing energy has been updated. New searches have been developed to cover a wider range of slepton signals. These include single electrons, acoplanar leptons accompanied by two photons plus missing energy as well as particles with lifetime. No evidence for the production of any such particles is found. Slepton mass limits are reported within gravity mediated and gauge mediated SUSY breaking scenarios. (C) 1998 Elsevier Science B.V. All rights reserved.

Amplitude analysis and branching fraction measurement of Ds+→K−K+π+π0

2021

We report an amplitude analysis and branching fraction measurement of Ds+→K+K−π+ decay using a data sample of 3.19 fb−1 recorded with BESIII detector at a center-of-mass energy of 4.178 GeV. We perform a model-independent partial wave analysis in the low K+K− mass region to determine the K+K− S-wave line shape, followed by an amplitude analysis of our very pure high-statistics sample. With the detection efficiency based on the amplitude analysis results, the absolute branching fraction is measured to be B(Ds+→K+K−π+)=(5.47±0.08stat±0.13sys)%.

Search for the weak decayη′→K±π∓and precise measurement of the branching fractionB(J/ψ→ϕη′)

2016

We present the first search for the rare decay of eta' into K-+/- pi(-/+) in J/psi -> phi eta', using a sample of 1.3 x 10(9) J/psi events collected with the BESIII detector. No significant signal is observed, and the upper limit at the 90% confidence level for the ratio B(eta' -> K-+/- pi(-/+))/B(eta' -> gamma pi(+/-) pi(-/+)) is determined to be 1.3 x 10(-4). In addition, we report the measurement of the branching fraction of J/psi -> phi eta' to be [5.10 +/- 0.03(stat) +/- 0.32(syst)] x 10(-4), which agrees with previous results from BESII.

Observation of charmless hadronic B decays

1996

Four candidates for charmless hadronic B decay are observed in a data sample of four million hadronic Z decays recorded by the ALEPH detector at LEP. The probability that these events come from background sources is estimated to be less than 10(-6). The average branching of weakly decaying B hadrons (a mixture of B-d(0), B-s(0) and Lambda(b) weighted by their production The average branching ratio of weakly decaying B hadrons (a mixture of B-d(0) cross sections and lifetimes, here denoted B) into two long-lived charged hadrons (pions, kaons or protons) is measured to be Br(B-->h(+)h(-))=(1.7(-0.7)(+1.0)+/-0.2)x10(-5). The relative branching fraction Br(B-d(s)(0)-->pi(+)pi(-)(K-))/Br(B-d(s)(…

Measurement of the leptonic decay width of J/ψ using initial state radiation

2016

Physics letters / B 761, 98 - 103(2016). doi:10.1016/j.physletb.2016.08.011

Measurement of triple gauge-boson couplings at 172 GeV

1998

The triple gauge-boson couplings, αWΦ, αW and αBΦ, have been measured using 34 semileptonically and 54 hadronically decaying W+W- candidate events. The events were selected in the data recorded during 1996 with the ALEPH detector at 172 GeV, corresponding to an integrated luminosity of 10.65 pb-1. The triple gauge-boson couplings have been measured using optimal observables constructed from kinematic information of W+W- events. The results are in agreement with the Standard Model expectation.

Evidence for the decays of and *

2019

Abstract We study the hadronic decays of to the final states and , using an annihilation data sample of 567 pb-1 taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCII collider. We find evidence for the decays and with statistical significance of and , respectively. Normalizing to the reference decays and , we obtain the ratios of the branching fractions and to be and , respectively. The upper limits at the 90% confidence level are set to be and . Using BESIII measurements of the branching fractions of the reference decays, we determine % (&lt;0.68%) and % (&lt;1.9%). Here, the first uncertainties are statistical and the second systematic. The obtained branching …

Measurement of the strong coupling constant using τ decays

1993

The strong coupling constant is determined from the leptonic branching ratios, the lifetime, and the invariant mass distribution of the hadronic final state of the tau lepton, using data accumulated at LEP with the ALEPH detector. The strong coupling constant measurement, alpha(s), (m(tau)2) = 0.330 +/-0.046, evolved to the Z mass, yields alpha(s)(M(Z)2) = 0. 1 18 +/- 0.005. The error includes experimental and theoretical uncertainties, the latter evaluated in the framework of the Shifman, Vainshtein and Zakharov (SVZ) approach. The method allows the non-perturbative contribution to the hadronic decay rate to be determined to be 0.3 +/- 0.5% . RI Perrier, Frederic/A-5953-2011; ANTONELLI, AN…

Observation of ψ(3686)→η′e+e−

2018

Abstract Using a data sample of 448.1 × 10 6 ψ ( 3686 ) events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay ψ ( 3686 ) → η ′ e + e − , with significances of 7.0σ and 6.3σ when reconstructing the η ′ meson via its decay modes η ′ → γ π + π − and η ′ → π + π − η ( η → γ γ ), respectively. The weighted average branching fraction is determined to be B ( ψ ( 3686 ) → η ′ e + e − ) = ( 1.90 ± 0.25 ± 0.11 ) × 10 − 6 , where the first uncertainty is statistical and the second systematic.

Observation of the Decay X(3872)→π0χc1(1P)

2019

Using a total of 9.0 fb(-1) of e(+)e(-) collision data with center-of-mass energies between 4.15 and 4.30 GeV collected by the BESIII detector, we search for the processes e(+)e(-) gamma X(3872) with X(3872) -> pi(0)chi(cJ) for J = 0, 1, 2. We report the first observation of X(3872) -> pi(0)chi(c1), a new decay mode of the X(3872), with a statistical significance of more than 5 sigma for all systematic fit variations. Normalizing to the previously established process e(+)e(-) -> gamma X(3872) with X(3872) -> pi(+) pi(-) J/psi, we find B(X(3872) -> pi(0)chi(c1))/B(X(3872) -> pi+ pi(-) J/psi) = 0.88(-0.27)(+0.33) +/- 0.10, where the first error is statistical and the second is systematic. We …

Tau hadronic branching ratios

1996

From 64492 selected tau-pair events, produced at the Zeta(o) resonance, the measurement of the tau decays into hadrons from a global analysis using 1991, 1992 and 1993 ALEPH data is presented. Special emphasis is given to the reconstruction of photons and pi(o)'s, and the removal of fake photons. A detailed study of the systematics entering the pi(o) reconstruction is also given. A complete and consistent set of tau hadronic branching ratios is presented for 18 exclusive modes. Most measurements are more precise than the present world average. The new level of precision reached allows a stringent test of tau - mu universality in hadronic decays, g(tau)/g(mu) = 1.0013 +/- 0.0095, and the fir…

Observation of a near-threshold enhancement in the ΛΛ¯ mass spectrum from e+e−→ϕΛΛ¯ at s from 3.51 to 4.60 GeV

2021

The process e(+)e(-) -> phi Lambda(Lambda) over bar is studied using data samples collected with the BESIII detector at the BEPCII Collider at center of mass energies root S ranging from 3.51 Ge ...

Observation of a00(980)−f0(980) Mixing

2018

We report the first observation of a(0)(0)(980)-f(0)(980) mixing in the decays of J/psi -> phi f(0)(980) -> phi a(0)(0)(980) -> phi eta pi(0) and chi(c1) -> a(0)(0)(980)pi(0) -> f(0)(980)pi(0)->pi(+)pi(-)pi(0), using data samples of 1.31 x 10(9) J/psi events and 4.48 x 10(8) psi (3686) events accumulated with the BESIII detector. The signals of f(0)(980) -> a(0)(0)(980) and a(0)(0)(980) -> f(0)(980) mixing are observed at levels of statistical significance of 7.4 sigma and 5.5 sigma, respectively. The corresponding branching fractions and mixing intensities are measured and the constraint regions on the coupling constants, g(a0K+K-) and g(f0K+K-), are estimated. The results improve the unde…

Production and decay of charmed mesons at the Z resonance

1991

Abstract In a sample of 190 000 hadronic Z decays, three signals of charm production are observed: two from the exclusive decays D ° → K − π + and D ∗+ → D °π + → K − π + π + and one in the transverse-momentum distribution of soft hadrons relative to the nearest jet. The features of these signals are in good agreement with expectations based on the standard model and previous measurements of the branching fractions. The number of D ∗± → K ± π ± π ± per hadronic decay of the Z is measured to be (5.11±0.34) × 10 −3 , and the branching ratio B(D 0 → K − π + ) is (3.62 ± 0.34 ± 0.44)%. Charm hadronization has been studied. The average fraction of the beam energy carried by the D ∗ meson is foun…

Measurement of the D∗± cross section in two photon collisions at LEP

1995

Abstract The inclusive production of D ∗± mesons in photon-photon collisions has been measured by the Aleph experiment at LEP with a beam energy of 45 GeV. The D ∗+ are detected in their decay to D 0 π + with the D 0 observed in three separate decay modes: (1) K − π + , (2) K − π + π 0 and (3) K − π + π − π + , and analagously for the D ∗− modes. A total of 33 events was observed from an integrated luminosity of 73 pb −1 which corresponds to a cross section for Σ( e + e − → e + e − D ∗± X ) of 155 ± 33 ± 21 pb. This result is compatible with both the direct production γγ → c c in the Born approximation and with a more complete calculation which includes both radiative QCD corrections and co…

Observation of ${{e^+e^- \rightarrow D_s^+} \overline{ D}^{\bf (*)0} {K^-}}$ and study of the P -wave ${{D_s}}$ mesons

2018

Studies of $e^+e^- \to D_s^+ \overline{D}{}^{(*)0}K^-$ and the $P$-wave charmed-strange mesons are performed based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567 pb$^{-1}$ collected with the BESIII detector at $\sqrt{s}= 4.600$ GeV. The processes of $e^+e^-\to D_s^+ \overline{D}{*}^{0} K^-$ and $D_s^+ \overline{D}{}^{0} K^-$ are observed for the first time and are found to be dominated by the modes $D_s^+ D_{s1}(2536)^-$ and $D_s^+ D^*_{s2}(2573)^-$, respectively. The Born cross sections are measured to be $\sigma^{B}(e^+e^-\to D_s^+ \overline{D}{*}^{0} K^-) = (10.1\pm2.3\pm0.8) pb$ and $\sigma^{B}(e^+e^-\to D_s^+ \overline{D}{}^{0} K^-) = (19.4\pm2.3\…

Observation of the decay D0→ρ−μ+νμ

2021

Measurement ofD s + meson production inZ decays and of theB s 0 lifetime

1995

D + mesons produced inZ 0→bb events were separated from theZ 0→cc component using a lifetime tag. Using a sample of 1.5 million hadronicZ decays collected with theAleph detector theB 0 andD s + yields have been measured: $$\begin{gathered} \hfill B(b \to \bar B_s^0 )B(\bar B_s^0 \to D_s^ + ) = 0.088 \pm 0.020(stat.) \\ \hfill \pm 0.020(stat.) \\ \hfill B(c \to D_s^ + ) = 0.088 \pm 0.020(stat.)_{ - 0.016}^{ + 0.019} (syst.) \\ \end{gathered} $$ TheB 0 lifetime was measured in aB 0 enriched sample reconstructing the decay length from the vertex of theD + with a hadron from theB 0 decay. The result obtained is: $$\tau _{B_s } = 1.61_{ - 0.29}^{ + 0.30} (stat.)_{ - 0.016}^{ + 0.018} (syst.)$$ p…

Measurement of the branching fraction for ψ(3770) → γχc0

2016

Kolcu, Onur Buğra (Arel Author) --- Makale 70 yazarlıdır.

Measurement of the

1997

A new method is presented for the measurement of the mean $\tau$ lepton lifetime using events in which $\tau$'s are pair-produced and both $\tau$'s decay to hadrons and $\nu_\tau$. Based on the correlation between the two $\tau$'s produced at a symmetric $e^+ e^-$ collider, the 3DIP method relies on the three-dimensional information from a double-sided vertex detector and on kinematic constraints for the precise measurement of the $\tau$ decay angles. Using the data collected from 1992 to 1994 with the ALEPH detector at LEP, a $\tau$ lifetime of $288.0 \pm 3.1 \pm 1.3 $\fs is obtained from the sample in which both $\tau$'s decay to one charged track, and $292.8 \pm 5.6 \pm 3.0 $\fs from the…

Study ofψdecays to theΞ−Ξ¯+andΣ(1385)∓Σ¯(1385)±final states

2016

We study the decays of the charmonium resonances J/psi and psi(3686) to the final states Xi(-)(Xi) over bar (+), S(1385)(-/+)(Sigma) over bar (1385)(+/-) based on a single baryon tag method using data samples of (223.7 +/- 1.4) x 10(6) J/psi and (106.4 +/- 0.9) x 10(6) psi(3686) events collected with the BESIII detector at the BEPCII collider. The decay psi(3686) -> Sigma(1385)(-/+)(Sigma) over bar (1385)(+/-) is observed for the first time, and the measurements of the other processes, including the branching fractions and angular distributions, are in good agreement with, and much more precise than, the previously published results. Additionally, the ratios B(psi(3686)->Xi(-)(Xi) over bar …

Measurements of |Vcb|, form factors and branching fractions in the decays → ℓ and → ℓ

1997

Two samples of exclusive semileptonic decays, 579 B0 -> D*+l-νl events and 261 B0 -> D+l-νl events, are selected from approximately 3.9 million hadronic Z decays collected by the ALEPH detector at LEP. From the reconstructed differential decay rate of each sample, the product of the hadronic form factor F(ω) at zero recoil of the D(*)+ meson and the CKM matrix element Vcb are measured to be FD*+ (1) Vcb = (31.9 +/- 1.8stat +/- 1.9syst) × 10-3,FD+ (1) Vcb = (27.8 +/- 6.8stat +/- 6.5syst) × 10-3. The ratio of the form factorsFD+ (1) and FD*+ (1) is measured to beFD+ (1)/FD*+ (1) = 0.87 +/- 0.22stat +/- 0.21syst. A value of Vcb is extracted from the two samples, using theoretical constraints o…

Observation of D+→f0(500)e+νe and Improved Measurements of D→ρe+νe

2019

Using a data sample corresponding to an integrated luminosity of 2.93 fb(-1) recorded by the BESIII detector at a center-of-mass energy of 3.773 GeV, we present an analysis of the decays D-0 -> ...

Measurement of the W mass by direct reconstruction in e+e- collisions at 172 GeV

1998

The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 10.65 pb(-1) collected with the ALEPH detector at a mean centre-of-mass energy of 172.09 GeV. The invariant mass distribution of simulated events are fitted to the experimental; distributions and the following W masses are obtained: WW --> , m(W) = 81.30 +/- 0.47(stat.) +/- 0.11(syst.)GeV/c(2), WW --> l nu (l=e,mu), m(W) = 80.54 +/- 0.47(stat.) +/- 0.11(syst.)GeV/c(2), WW --> tau nu, m(W) = 79.56 +/- 1.08(stat.) +/- 0.23(syst.) GeV/c(2). The statistical errors are the expected errors for Monte Carlo samples of the same integrated luminosity as the data…

Measurements of absolute branching fractions forΛc+→Ξ0K+and Ξ(1530)0K+

2018

Abstract We report the first measurements of absolute branching fractions for the W -exchange-only processes Λ c + → Ξ 0 K + and Λ c + → Ξ ( 1530 ) 0 K + with the double-tag technique, by analyzing an e + e − collision data sample, that corresponds to an integrated luminosity of 567 pb −1 collected at a center-of-mass energy of 4.6 GeV by the BESIII detector. The branching fractions are measured to be B ( Λ c + → Ξ 0 K + ) = ( 5.90 ± 0.86 ± 0.39 ) × 10 − 3 and B ( Λ c + → Ξ ( 1530 ) 0 K + ) = ( 5.02 ± 0.99 ± 0.31 ) × 10 − 3 , where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.

Measurement of the branching fractions of Ds+→η′X and Ds+→η′ρ+ in e+e−→Ds+Ds−

2015

We study D-s(+) decays to final states involving the eta' with a 482 pb(-1) data sample collected at root s = 4.009 GeV with the BESIII detector at the BEPCII collider. We measure the branching fractions B(D-s(+) -> eta'X) = (8.8 +/- 1.8 +/- 0.5)% and B(D-s(+) > eta'rho(+)) = (5.8 +/- 1.4 +/- 0.4)% where the first uncertainty is statistical and the second is systematic. In addition, we estimate an upper limit on the non-resonant branching ratio B(D-s(+) -> eta'pi(+)pi(0)) eta'rho(+)). (C) 2015 The Authors. Published by Elsevier B.V.

A measurement of the QCD colour factors and a limit on the light gluino

1997

Using data collected from 1992 to 1995 with the ALEPH detector at LEP, a measurement of the colour factor ratios C-A/C-F and T-F/C-F and the strong coupling constant = C-F alpha(s), (M-Z)/(2 pi) has been performed by fitting theoretical predictions simultaneously to the measured differential two-jet rate and angular distributions in four-jet events. The result is found to be in excellent agreement with QCD. C-A/C-F = 2.20 +/- 0.09 (stat) +/- 0.13 (syst), T-F/C-F = 0.29 +/- 0.05 (stat) +/- 0.06 (syst). Fixing C-A/C-F and T-F/C-F to the QCD values permits a determination of alpha(s) (M-Z) and n(f), the number of active flavours. With this measurement the existence of a gluino with mass below …

Measurement of the cross section for e+e−→ΛΛ¯ and evidence of the decay ψ(3770)→ΛΛ¯

2021

Measurement of the branching fraction of and search for a CP -violating asymmetry in η′→π+π−e+e− at BESIII

2021

The rare decay η′ → π+π−e+e− is studied using a sample of 1.3×109  J/ψ events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precisi ...

Correlation measurements in Z→τ+τ− and the τ neutrino helicity

1994

Using data collected with the ALEPH detector at LEP correlations between the decay products of the τ+ and τ- produced in the decay of the Z have been measured. The measurements performed in the decays τ-->πν and τ-->ϱν place limits on deviations from the Standard Model. These are given by the parameter ζ with ζ = -1 for the Standard Model. The measured values are ζπ = -0.95 +/- 0.11 +/- 0.05 and ζϱ = -1.03 +/- 0.11 +/- 0.05. For models which predict ζπ = ζϱ = ζ - interpreted as the average τ neutrino helicity - the measurement is ζ = -0.99 +/- 0.07 +/- 0.04.

Determination of the absolute branching fractions of D0→K−e+νe and D+→K¯0e+νe

2021

Using 2.93 fb$^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at a center-of-mass energy of 3.773~GeV, we measure the absolute branching fractions of the decays $D^0\to K^-e^+\nu_e$ and $D^+\to \bar K^0 e^+\nu_e$ to be $(3.574\pm0.031_{\rm stat}\pm 0.025_{\rm syst})\%$ and $(8.70\pm0.14_{\rm stat}\pm 0.16_{\rm syst})\%$, respectively. Starting with the process $e^+e^-\to D\bar{D}$, a new reconstruction method is employed to select events that contain candidates for both $D\to \bar Ke^+\nu_e$ and $\bar D\to Ke^-\bar \nu_e$ decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events conta…

Measurement of the absolute branching fraction of Λc+→pKS0η decays

2021

Abstract Based on 586 p b − 1 of e + e − annihilation data collected at a center-of-mass energy of s = 4.6 GeV with the BESIII detector at the BEPCII collider, the absolute branching fraction of Λ c + → p K S 0 η decays is measured for the first time to be B ( Λ c + → p K S 0 η ) = ( 0.414 ± 0.084 ± 0.028 ) % , where the first uncertainty is statistical and the second is systematic. The result is compatible with a previous CLEO result on the relative branching fraction B ( Λ c + → p K S 0 η ) B ( Λ c + → p K − π + ) , and consistent with theoretical predictions of SU(3) flavor symmetry.

Study of the process e+e−→ϕη at center-of-mass energies between 2.00 and 3.08 GeV

2021

We study the process e^+e^− → π^+π^−ηγ, where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BABAR data sample with an integrated luminosity of 469  fb^(-1). Using the π^+π^−η invariant mass spectrum, we measure the e^+e^− → π^+π^−η cross section in the e^+e^− center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson dominance model with four ρ-like states. We observe 49±9 events of the J/ψ decay to π^+π^−η and measure the product Γ_(J/Ψ → e^+e^−)B_(J/Ψ → π^+π^−η) = 2.34 ± 0.43_(stat) ± 0.16_(syst)  eV.

Observation of a Resonant Structure in e+e−→K+K−π0π0

2020

A partial-wave analysis is performed for the process e^{+}e^{-}→K^{+}K^{-}π^{0}π^{0} at the center-of-mass energies ranging from 2.000 to 2.644 GeV. The data samples of e^{+}e^{-} collisions, collected by the BESIII detector at the BEPCII collider with a total integrated luminosity of 300  pb^{-1}, are analyzed. The total Born cross sections for the process e^{+}e^{-}→K^{+}K^{-}π^{0}π^{0}, as well as the Born cross sections for the subprocesses e^{+}e^{-}→ϕπ^{0}π^{0}, K^{+}(1460)K^{-}, K_{1}^{+}(1400)K^{-}, K_{1}^{+}(1270)K^{-}, and K^{*+}(892)K^{*-}(892), are measured versus the center-of-mass energy. The corresponding results for e^{+}e^{-}→K^{+}K^{-}π^{0}π^{0} and ϕπ^{0}π^{0} are consist…

ALEPH: a Detector for Electron-Positron Annihilations at LEP

1990

Process-centred Software Engineering Environments (PSEE) are the most recent generation of environments supporting software development activities. Most of PSEE are based on mechanisms promoting enforcement and automation of process activities. In this kind of mechanisms the process models are prescribed in a detailed and complete way. But the experience shows that supporting processes is more concerned with the flexibility of guidance offered during the process performance than with enforcement of a collection of predefined process models. In this paper, we present a solution to support strategic processes in a PSEE by providing a flexible guidance during process enactment.

Observation of pseudoscalar and tensor resonances in J /ψ →γφφ

2016

Based on a sample of (1310.6 +/- 10.5) x 10(6) J/psi events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay J/psi -> gamma phi phi is performed in order to study the intermediate states. Results of the partial wave analysis show that the structures are predominantly 0(-+) states. The existence of the eta(2225) is confirmed, and its resonance parameters are measured. Two additional pseudoscalar states, the eta(2100) with a mass of 2050(-24-26)(+30+75) MeV/c(2) and a width of 250(-30-164)(+36+181) MeV/c(2) and the X(2500) with a mass of 2470(-19-23)(+15+101) MeV/c(2) and a width of 230(-35-33)(+64+56) MeV/c(2), are observed. In add…

Observation of ψ(3686)→e+e−χcJ and χcJ→e+e−J/ψ

2018

Using 4.479 x 10(8) psi(3686) events collected with the BESIII detector, we search for the decays psi(3686) -> e(+)e(-)chi(cJ) and chi(cJ) -> e(+)e(-)J/psi, where J = 0, 1, 2. The decays psi(3686) -> e(+)e(-)chi(cJ) and chi(cJ) -> e(+)e(-)J/psi are observed for the first time. The measured branching fractions are B(psi(3686) -> e(+)e(-)chi(cJ)) = (11.7 +/- 2.5 +/- 1.0) x 10(-4), (8.6 +/- 0.3 +/- 0.6) x 10(-4), (6.9 +/- 0.5 +/- 0.6) x 10(-4) for J = 0, 1, 2, and B(chi(cJ) -> e(+)e(-)J/psi) = (1.51 +/- 0.30 +/- 0.13)x10(-4), (3.73 +/- 0.09 +/- 0.25)x10(-3), (2.48 +/- 0.08 +/- 0.16)x10(-3) for J = 0, 1, 2, respectively. The ratios of the branching fractions B(psi(3686) -> e(+)e(-)chi(cJ))/B(ps…

Study of $e^{+}e^{-} \to D^{+} D^{-} \pi^{+} \pi^{-} $ at center-of-mass energies from 4.36 to 4.60 GeV

2020

We report a study of the $e^{+}e^{-} \to D^{+} D^{-} \pi^{+} \pi^{-}$ process using $e^{+}e^{-}$ collision data samples with an integrated luminosity of $2.5\,\rm{fb}^{-1}$ at center-of-mass energies from 4.36 to $4.60 \rm{GeV}$, collected with the BESIII detector at the BEPCII storage ring. The $D_{1}(2420)^+$ is observed in the $D^{+} \pi^{+} \pi^{-}$ mass spectrum. The mass and width of the $D_{1}(2420)^+$ are measured to be $(2427.2\pm 1.0_{\rm stat.}\pm 1.2_{\rm syst.}) \rm{MeV}/c^2$ and $(23.2\pm 2.3_{\rm stat.} \pm2.3_{\rm syst.}) \rm{MeV}$, respectively. The first errors are statistical and the second ones are systematic. In addition, the Born cross sections of the $e^{+}e^{-} \to D…

A measurement of the gluon splitting rate into bb̄ pairs in hadronic Z decays

1998

Abstract A measurement of the fraction of hadronic Z decays in which a gluon splits into a b b pair, g b b , is presented using data collected by ALEPH from 1992 to 1995 at the Z resonance. The selection is based on four-jet events. Events are selected by means of topological cuts and a lifetime tag. The result is g b b =(2.77±0.42 (stat)±0.57 (syst))×10 −3 .

Study of J/ψ and ψ(3686) decays to π+π−η′

2017

Using the data samples of 1.31 x 10(9) J/psi events and 4.48 x 10(8) psi(3686) events collected with the BESIII detector, partial wave analyses on the decays J/psi and psi(3686) pthornp -> pi(+)pi(-)eta' are performed with a relativistic covariant tensor amplitude approach. The dominant contribution is found to be J/psi and psi(3686) decays to rho eta' In the J/psi decay, the branching fraction B(J/psi -> rho eta') is determined to be (7.90 +/- 0.19(stat) +/- 0.49(sys)) x 10(-5). Two solutions are found in the psi(3686) decay, and the corresponding branching fraction B(psi(3686) -> rho eta') is (1.02 +/- 0.11(stat) +/- 0.24(sys)) x 10(-5) for the case of destructive interference, and (5.69 …

First Measurement of the Form Factors in Ds+→K0e+νe and Ds+→K*0e+νe Decays

2019

We report on new measurements of Cabibbo-suppressed semileptonic D_{s}^{+} decays using 3.19  fb^{-1} of e^{+}e^{-} annihilation data sample collected at a center-of-mass energy of 4.178 GeV with the BESIII detector at the BEPCII collider. Our results include branching fractions B(D_{s}^{+}→K^{0}e^{+}ν_{e})=[3.25±0.38(stat)±0.16(syst)]×10^{-3} and B(D_{s}^{+}→K^{*0}e^{+}ν_{e})=[2.37±0.26(stat)±0.20(syst)]×10^{-3}, which are much improved relative to previous measurements, and the first measurements of the hadronic form-factor parameters for these decays. For D_{s}^{+}→K^{0}e^{+}ν_{e}, we obtain f_{+}(0)=0.720±0.084(stat)±0.013(syst), and for D_{s}^{+}→K^{*0}e^{+}ν_{e}, we find form-factor r…

Measurements of cross section of e+e−→pp¯π0 at center-of-mass energies between 4.008 and 4.600 GeV

2017

Based on e(+)e(-) annihilation data samples collected with the BESIII detector at the BEPCII collider at 13 center-of-mass energies from 4.008 to 4.600 GeV, measurements of the Born cross section o ...

Measurements of the branching fractions for D+→KS0KS0K+, KS0KS0π+ and D0→KS0KS0, KS0KS0KS0

2017

Abstract By analyzing 2.93 fb − 1 of data taken at the ψ ( 3770 ) resonance peak with the BESIII detector, we measure the branching fractions for the hadronic decays D + → K S 0 K S 0 K + , D + → K S 0 K S 0 π + , D 0 → K S 0 K S 0 and D 0 → K S 0 K S 0 K S 0 . They are determined to be B ( D + → K S 0 K S 0 K + ) = ( 2.54 ± 0.05 s t a t . ± 0.12 s y s . ) × 10 − 3 , B ( D + → K S 0 K S 0 π + ) = ( 2.70 ± 0.05 s t a t . ± 0.12 s y s . ) × 10 − 3 , B ( D 0 → K S 0 K S 0 ) = ( 1.67 ± 0.11 s t a t . ± 0.11 s y s . ) × 10 − 4 and B ( D 0 → K S 0 K S 0 K S 0 ) = ( 7.21 ± 0.33 s t a t . ± 0.44 s y s . ) × 10 − 4 , where the second one is measured for the first time and the others are measured wit…

Study of decay dynamics andCPasymmetry inD+→KL0e+νedecay

2015

Using 2.92 fb(-1) of electron-positron annihilation data collected at root s = 3.773 GeV with the BESIII detector, we obtain the first measurements of the absolute branching fraction B(D+ -> K(L)(0)e(+)nu(e)) = (4.481 +/- 0.027(stat) +/- 0.103(sys))% and the CP asymmetry A(CP)(D+-> KL0e+nu e) = (-0.59 +/- 0.60(stat) +/- 1.48(sys))%. From the D+ -> K(L)(0)e(+)nu(e) differential decay rate distribution, the product of the hadronic form factor and the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element, f(+)(K)(0)vertical bar V-cs vertical bar, is determined to be 0.728 +/- 0.006(stat) +/- 0.011(sys). Using vertical bar V-cs vertical bar from the SM constrained fit with the measured f(+)…

Measurement of the Born cross sections for e+e−→η′π+π− at center-of-mass energies between 2.00 and 3.08 GeV

2021

The Born cross sections for the process $e^+e^- \to \eta^\prime \pi^{+}\pi^{-}$ at different center-of-mass energies between $2.00$ and $3.08$~GeV are reported with improved precision from an analysis of data samples collected with the BESIII detector operating at the BEPCII storage ring. An obvious structure is observed in the Born cross section line shape. Fit as a Breit-Wigner resonance, it has a statistical significance of $6.3\sigma$ and a mass and width of $M=(2108\pm46\pm25)$~MeV/$c^2$ and $\Gamma=(138\pm36\pm30)$~MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in $e^+e^- \to \eta^\pri…

Amplitude analysis and branching-fraction measurement of D-s(+) -> K-S(0)pi(+)pi(0)

2022

Journal of high energy physics 2021(6), 181 (2021). doi:10.1007/JHEP06(2021)181

The experimental facility for the Search for Hidden Particles at the CERN SPS

2019

The Search for Hidden Particles (SHiP) Collaboration has shown that the CERN SPS accelerator with its 400 $\mathrm{\small GeV/c}$ proton beam offers a unique opportunity to explore the Hidden Sector. The proposed experiment is an intensity frontier experiment which is capable of searching for hidden particles through both visible decays and through scattering signatures from recoil of electrons or nuclei. The high-intensity experimental facility developed by the SHiP collaboration is based on a number of key features and developments which provide the possibility of probing a large part of the parameter space for a wide range of models with light long-lived superweakly interacting particles…

Measurement of the doubly Cabibbo-suppressed decay D+→K+π+π−π0 with semileptonic tags

2021

A new limit on the CP violating decay KS→3π0 with the KLOE experiment

2013

We have carried out a new direct search for the CP violating decay K-S -> 3 pi(0) with 1.7 fb(-1) of e(+)e(-) collisions collected by the KLOE detector at the Phi-factory DA Phi NE. We have searched for this decay in a sample of about 5.9 x 10(8) KSKL events tagging the K-S by means of the K-L interaction in the calorimeter and requiring six prompt photons. With respect to our previous search, the analysis has been improved by increasing of a factor four the tagged sample and by a more effective background rejection of fake K-S tags and spurious clusters. We find no candidates in data and simulated background samples, while we expect 0.12 standard model events. Normalizing to the number of …

Measurement of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII

2021

Physics letters / B 817, 136328 (2021). doi:10.1016/j.physletb.2021.136328

Measurement of the η→3π0 slope parameter α with the KLOE detector

2010

Abstract We present a measurement of the slope parameter α for the η → 3 π 0 decay, with the KLOE experiment at the DAΦNE ϕ -factory, based on a background free sample of ∼17 million η mesons produced in ϕ radiative decays. By fitting the event density in the Dalitz plot we determine α = − 0.0301 ± 0.0035 stat − 0.0035 + 0.0022 syst . The result is in agreement with recent measurements from hadro- and photo-production experiments.

Measurement of the B hadron lifetime

1991

The average lifetime of B hadrons has been measured by the ALEPH experiment at LEP. Events containing B hadrons are selected by the identification of leptons with high transverse momentum in hadronic Z decays, and the lifetime is extracted from a fit to the impact parameter distribution of the lepton tracks. From a sample of 1.7×105 hadronic Z decays a lifetime of 1.29±0.06±0.10 ps is measured.

Measurement of B- mixing at the Z

1991

Abstract From more than 175 000 hadronic Z decays observed with the ALEPH detector at LEP, we select 823 events with pairs of leptons in the final state. From these we measure χ , the probability thata b hadron which is observed to decay originated as a b hadron. We find χ =0.132 −0.026 +0.027 .

Measurement of the strong coupling constant alfa_s from global event-shape variables of hadronic Z decays

1991

Abstract An analysis of global event-shape variables has been carried out for the reaction e+e−→Z0→hadrons to measure the strong coupling constant αs. This study is based on 52 720 hadronic events obtained in 1989/90 with the ALEPH detector at the LEP collider at energies near the peak of the Z-resonance. In order to determine αs, second order QCD predictions modified by effects of perturbative higher orders and hadronization were fitted to the experimental distributions of event-shape variables. From a detailed analysis of the theoretical uncertainties we find that this approach is best justified for the differential two-jet rate, from which we obtain αs(MZ2) = 0.121 ± 0.002(stat.)±0.003(s…

Study of the D0 → K− μ+ νμ Dynamics and Test of Lepton Flavor Universality with D0→K−l+νl Decays

2020

Search for the decay Ds+→a0(980)0e+νe

2021

Using 6.32 fb$^{-1}$ of electron-positron collision data recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, we present the first search for the decay $D_s^+\to a_0(980)^0 e^+\nu_e,\,a_0(980)^0\rightarrow \pi^0\eta$, which could proceed via $a_0(980)$-$f_0(980)$ mixing. No significant signal is observed. An upper limit of $1.2 \times 10^{-4}$ at the $90\%$ confidence level is set on the product of the branching fractions of $D_{s}^{+}\to a_0(980)^0 e^+\nu_e$ and $a_0(980)^0\rightarrow \pi^0\eta$ decays.

Future Physics Programme of BESIII

2020

There has recently been a dramatic renewal of interest in the subjects of hadron spectroscopy and charm physics. This renaissance has been driven in part by the discovery of a plethora of charmonium-like $XYZ$ states at BESIII and $B$ factories, and the observation of an intriguing proton-antiproton threshold enhancement and the possibly related $X(1835)$ meson state at BESIII, as well as the threshold measurements of charm mesons and charm baryons. We present a detailed survey of the important topics in tau-charm physics and hadron physics that can be further explored at BESIII over the remaining lifetime of BEPCII operation. This survey will help in the optimization of the data-taking pla…

Cross section measurement of e+e−→pp¯η and e+e−→pp¯ω at center-of-mass energies between 3.773 GeV and 4.6 GeV

2021

Using data samples with a total integrated luminosity of $20.1~\rm fb^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the cross section of the process $e^+e^- \rightarrow \pi^+\pi^-\psi(3686)$ is measured at center-of-mass energies between 4.0076 and 4.6984 GeV. The measured cross section is consistent with previous results, but with much improved precision. A fit to the measured energy-dependent cross section, which includes three Breit-Wigner functions and a non-resonant contribution, confirms the existence of the charmonium-like states $Y(4220)$, $Y(4390)$, and $Y(4660)$. This is the first observation of the $Y(4660)$ at the BESIII experiment.

Determination of A(FB)(b) using jet charge measurements in Z decays

1998

An improved measurement of the forward-backward asymmetry in Z --> b (b) over bar decays is presented, based on a sample of 4.1 million hadronic Z decays collected by ALEPH between 1991 and 1995. Data are analysed as a function of polar angle of the event axis and b purity. The event tagging efficiency and mean b-jet hemisphere charge are measured directly from data. From the measured forward-backward jet charge asymmetry, the b quark asymmetry at root s= m(Z) is determined to be: A(FB)(b) = 0.1017 +/- 0.0032(syst.) +/- 0.0032(syst.). In the context of the Standard Model this corresponds to a value of the effective weak mixing angle of sin(2) theta(W)(eff)= 0.23109 +/- 0.00096. (C) 1998 Pub…

Measurements of the branching fractions of $\psi(3686)\rightarrow\bar{\Sigma}^{0}\Lambda+c.c.$ and $\chi_{cJ (J = 0,1,2)} \rightarrow \Lambda \bar{\L…

2021

Based on $4.481\times10^8$ $\psi(3686)$ events collected with the BESIII detector at BEPCII, the branching fraction of the isospin violating decay $\psi(3686)\rightarrow\bar{\Sigma}^{0}\Lambda+c.c.$ is measured to be $(1.60 \pm 0.31 \pm 0.13~\pm~0.58) \times 10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is the uncertainty arising from interference with the continuum. This result is significantly smaller than the measurement based on CLEO-c data sets. The decays $\chi_{cJ} \rightarrow\Lambda\bar{\Lambda}$ are measured via $\psi(3686)\rightarrow\gamma\chi_{cJ}$, and the branching fractions are determined to be $\mathcal{B}\left(\chi_{c0}\rightar…

Cross section measurement of e+e−→pp¯η and e+e−→pp¯ω at center-of-mass energies between 3.773 GeV and 4.6 GeV

2021

Study of the $e^+e^- \to \pi^{+}\pi^{-}\omega$ process at center-of-mass energies between 4.0 and 4.6 GeV

2023

Using $15.6$ $\rm fb^{-1}$ of $e^+e^-$ collision data collected at twenty-four center-of-mass energies from $4.0$ to $4.6$ GeV with the BESIII detector, the helicity amplitudes of the process $e^+e^-\to \pi^{+}\pi^{-}\omega$ are analyzed for the first time. Born cross section measurements of two-body intermediate resonance states with statistical significance greater than 5$\sigma$ are presented, such as $f_{0}(500)$, $f_{0}(980)$, $f_{2}(1270)$, $f_{0}(1370)$, $b_{1}(1235)^{\pm}$, and $\rho(1450)^{\pm}$. In addition, evidence of a resonance state in $e^+e^-\to \pi^+\pi^-\omega$ production is found. The mass of this state obtained by line shape fitting is about 4.2 GeV/$c^2$, which is consi…

Measurement of $\Lambda$ transverse polarization in $e^{+}e^{-}$ collisions at $\sqrt{s}= 3.68-3.71$ GeV

2023

With data samples collected with the BESIII detector at seven energy points at $\sqrt{s}= 3.68 - 3.71$ GeV, corresponding to an integrated luminosity of 333 pb$^{-1}$, we present a study of the $\Lambda$ transverse polarization in the $e^+e^-\to\Lambda\bar\Lambda$ reaction. The significance of polarization by combining the seven energy points is found to be 2.6$\sigma$ including the systematic uncertainty, which implies a non-zero phase between the transition amplitudes of the $\Lambda\bar\Lambda$ helicity states. The modulus ratio and the relative phase of EM-$psionic$ form factors combined with all energy points are measured to be $R^{\Psi} =$ 0.71$^{+0.10}_{-0.10}$ $\pm$ 0.03 and $\Delta…

Improved tau polarisation measurement

1996

Using 22 pb−1 of data collected at LEP in 1992 on the peak of the Z resonance, the ALEPH collaboration has measured the polarisation of the tau leptons decaying into $$ev\bar v, \mu v\bar v$$ ,πν, ρν and a1 ν from their individual decay product distributions. The measurement of the tau polarisation as a function of the production polar angle yields the two parametersN τ andN e, where, in terms of the axial and vector couplingsg Al andg Vl,N l=2g Vl gAl/(g Vl 2 +g 2 ). This analysis follows to a large extent the methods devised for the 1990 and 1991 data but with improvements which bring a better understanding of the systematic uncertainties. Combining the 1992 measurements with our previous…

Measurement of the Branching Fraction for the Decay $\psi(3686) \rightarrow \phi K_{S}^{0} K_{S}^{0}$

2023

Based on $(448.1 \pm 2.9 )\times 10^6$ $\psi(3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decay $\psi(3686)\rightarrow \phi K_{S}^{0} K_{S}^{0}$ is observed for the first time. Taking the interference between $\psi(3686)$ decay and continuum production into account, the branching fraction of this decay is measured to be $\mathcal{B}(\psi(3686)\rightarrow\phi K_S^0 K_S^0 )$ = $(3.53 $ $\pm$ $0.20$ $\pm$ $0.21$)$\times 10^{-5}$, where the first uncertainty is statistical and the second is systematic. Combining with the world average value for ${\mathcal B}(J/\psi\to \phi K^0_SK^0_S)$, the ratio $\mathcal{B}(\psi(3686)\rightarrow \phi K_{S}^{0} K_{S}^{…

Observation of an a 0 -like State with Mass of 1.817 GeV in the Study of D s + → K S 0 K + π 0 Decays

Measurement of the branching fraction for ψ(3686)→ωKS0KS0

2021

Analyzing (448.1±2.9)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider, the ψ(3686)→ωKS0KS0 decay is observed for the first time. The branching fraction for this decay is determined to be Bψ(3686)→ωKS0KS0=(7.04±0.39±0.36)×10−5, where the first uncertainty is statistical and the second is systematic.

Observation of the decay $D^+_s\to \omega\pi^+\eta$

2023

Using 7.33 fb$^{-1}$ of $e^+e^-$ collision data collected by the BESIII detector at center-of-mass energies between 4.128 and 4.226~GeV, we observe for the first time the decay $D^{\pm}_s\to \omega\pi^{\pm}\eta$ with a statistical significance of 7.6$\sigma$. The measured branching fraction of this decay is $(0.54\pm0.12\pm0.04)\%$, where the first uncertainty is statistical and the second is systematic.

Search for invisible decays of the Λ baryon

2022

Physical review / D 105(7), L071101 (2022). doi:10.1103/PhysRevD.105.L071101

Observation of the $\psi(1^3D_2)$ state in $e^+e^-\to\pi^+\pi^-\gamma\chi_{c1}$ at BESIII

2015

We report the observation of the $X(3823)$ in the process $e^+e^-\to \pi^+\pi^-X(3823) \to \pi^+\pi^-\gamma\chi_{c1}$ with a statistical significance of $6.2\sigma$, in data samples at center-of-mass energies $\sqrt{s}=$4.230, 4.260, 4.360, 4.420 and 4.600~GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the $X(3823)$ is $(3821.7\pm 1.3\pm 0.7)$~MeV/$c^2$, where the first error is statistical and the second systematic, and the width is less than $16$~MeV at the 90\% confidence level. The products of the Born cross sections for $e^+e^-\to \pi^+\pi^-X(3823)$ and the branching ratio $\mathcal{B}[X(3823)\to \gamma\chi_{c1,c2}]$ are also measu…

Updated measurement of the branching fraction of $D_s^+\to \tau^+\nu_\tau$ via $\tau^+\to\pi^+\bar{\nu}_\tau$

2023

We report the updated study of $D_s^+\to \tau^+\nu$ via $\tau^+\to\pi^+\bar{\nu}_\tau$ with a boosted decision trees analysis, with $7.33$ fb$^{-1}$ of $e^{+}e^{-}$ collision data collected by the BESIII detector at center-of-mass energies between $4.128$ and $4.226$~GeV. The branching fraction of $D_s^+\to \tau^+\nu_\tau$ is determined to be $(5.41\pm0.17_{\rm stat}\pm0.13_{\rm syst})\%$. The product of the $D_s^+$ decay constant $f_{D_s^+}$ and the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ is $f_{D_s^+}|V_{cs}| = (247.6\pm3.9_{\rm stat}\pm3.2_{\rm syst}\pm1.0_{\rm input})~\mathrm{MeV}$. Combining with the $|V_{cs}|$ obtained from the global fit in the Standard Model and the $f_{…

Search for a massless dark photon in $\Lambda^{+}_{c}\to p \gamma^{\prime}$ decay

2022

A search for a massless dark photon $\gamma^{\prime}$ is conducted using 4.5 $\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.600 and 4.699 $\mathrm{GeV}$ with the BESIII detector at BEPCII. No significant signal is observed, and the upper limit on the branching fraction $\mathcal{B}(\Lambda^{+}_{c}\to p \gamma^{\prime})$ is determined to be $8.0\times 10^{-5}$ at 90% confidence level.

Observation of the hindered electromagnetic Dalitz decay ψ(3686)→e+e−ηc

2022

Physical review / D 106(11), 112002 (2022). doi:10.1103/PhysRevD.106.112002

Measurement of cross section for $e^{+}e^{-}\rightarrow��^{0}\bar��^{0}$ near threshold

2021

Using $e^+e^-$ collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb$^{-1}$, we measure the cross sections and effective form factors for the process $e^{+}e^{-}\rightarrow��^{0}\bar��^{0}$ utilizing a single-tag method. A fit to the cross section of $e^{+}e^{-}\rightarrow��^{0}\bar��^{0}$ with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes $e^{+}e^{-}\rightarrow��^{-}\bar��^{+}$ and $��^{0}\bar��^{0}$ is calculated using recent BESIII mea…

Study of $e^+e^- \rightarrow ��^{0}X(3872)��$ and search for $Z_c(4020)^{0}\rightarrow X(3872)��$

2021

Using data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.178 to 4.600 GeV, we study the process $e^+e^-\rightarrow��^{0}X(3872)��$ and search for $Z_c(4020)^{0}\rightarrow X(3872)��$. We find no significant signal and set upper limits on $��(e^+e^-\rightarrow��^{0}X(3872)��)\cdot\mathcal{B}(X(3872)\rightarrow��^{+}��^{-}J/��)$ and $��(e^+e^-\rightarrow��^{0}Z_c(4020)^{0})\cdot\mathcal{B}(Z_c(4020)^{0}\rightarrow X(3872)��)\cdot\mathcal{B}(X(3872)\rightarrow��^{+}��^{-}J/��)$ for each energy point at $90\%$ confidence level, which is of the order of several tenths pb.

Observation of the $Y(4230)$ and a new structure in $e^+ e^- \rightarrow K^+ K^- J/\Psi^*$

2022

Chinese physics / C 46(11), 111002 (2022). doi:10.1088/1674-1137/ac945c

Tau leptonic branching ratios

1996

A sample of 62249 tau-pair events is selected from data taken with the ALEPH detector in 1991, 1992 and 1993. The measurement of the branching fractions for tau decays into electrons and muons is presented with emphasis on the study of systematic effects from selection, particle identification and decay classification. The results obtained are: B-e=17.79+/-0.12(stat)+/-0.06(syst)(%) and B-mu=17.31+/-0.11(stat)+/-0.05(syst)(%). Combined with the most recent ALEPH determination of the tau lifetime, these results provide a relative measurement of the leptonic couplings in the weak charged current for transverse W bosons: g(mu)/g(e)=1.0002+/-0.0051 and g(tau)/g(mu)=0.9943+/-0.0065. RI ANTONELLI…

Determination of sin2 θeff w using jet charge measurements in hadronic Z decays

2011

The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing the original quark and antiquark is measured for bb̄ and cc̄ events in subsamples selected by their long lifetimes or using fast D*'s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation between charges of opposite hemispheres and agrees with predictions of hadr…

Measurement of $Λ$ transverse polarization in $e^{+}e^{-}$ collisions at $\sqrt{s}= 3.68-3.71$ GeV

2023

With data samples collected with the BESIII detector at seven energy points at $\sqrt{s}= 3.68 - 3.71$ GeV, corresponding to an integrated luminosity of 333 pb$^{-1}$, we present a study of the $Λ$ transverse polarization in the $e^+e^-\toΛ\barΛ$ reaction. The significance of polarization by combining the seven energy points is found to be 2.6$σ$ including the systematic uncertainty, which implies a non-zero phase between the transition amplitudes of the $Λ\barΛ$ helicity states. The modulus ratio and the relative phase of EM-$psionic$ form factors combined with all energy points are measured to be $R^Ψ =$ 0.71$^{+0.10}_{-0.10}$ $\pm$ 0.03 and $ΔΦ^Ψ$ = (23$^{+8.8}_{-8.0}$ $\pm$ 1.6$)^\circ$…

Measurement of Prompt Photon Production In Hadronic-z Decays

1993

The production of isolated photons in hadronic Z decays is measured with the ALEPH detector at LEP using a sample of 450 000 hadronic events. The corrected rate is given for several values of the minimum invariant mass squared cut between the photon and the jets. This measurement of final state radiation from the quarks is compared with the predictions of parton shower models JETSET, ARIADNE and HERWIG as well as with the predictions of QCD matrix element calculations. RI Perrier, Frederic/A-5953-2011; ANTONELLI, ANTONELLA/C-6238-2011; Buttar, Craig/D-3706-2011; Stahl, Achim/E-8846-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; St.Denis, Richard/C-8997-2012; Forti, Franc…

Partial wave analysis of $J / ψ → γ η η ′$

2022

Physical review / D 105(7), 072002 (2022). doi:10.1103/PhysRevD.105.072002

Determination of the absolute branching fractions of D0→K−e+νe and D+→K¯0e+νe

2021

First measurement of polarizations in the decay $D^0 \to ωϕ$

2021

Using a data sample corresponding to an integrated luminosity of 2.93 fb$^{-1}$ collected at a center-of-mass energy $\sqrt{s}=3.773$ GeV by the BESIII detector, the decay $D^0 \toωϕ$ is observed for the first time. The branching fraction is measured to be $(6.48 \pm 0.96 \pm 0.40)\times 10^{-4}$ with a significance of $6.3 σ$, where the first and second uncertainties are statistical and systematic, respectively. An angular analysis reveals that the $ϕ$ and $ω$ mesons from the $D^0 \to ωϕ$ decay are transversely polarized. The $95\%$ confidence level upper limit on longitudinal polarization fraction is set to be less than $0.24$, which is inconsistent with current theoretical expectations a…

Improved measurement of the absolute branching fraction of inclusive semileptonic Λc+ decay

2023

Using 4.5 fb−1 of e+e− annihilation data samples collected at center-of-mass energies ranging from 4.600 to 4.698 GeV with the BESIII detector at the BEPCII collider, we measured the absolute branching fraction for the inclusive semileptonic decay Λc+→Xe+νe, where X refers to any possible particle system. The branching fraction of the decay is determined to be B(Λc+→Xe+νe)=(4.06±0.10stat±0.09syst)%. Our result improves the precision of previous measurements of B(Λc+→Xe+νe) by more than threefold. Using the known Λc+ lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons, we measure the ratio of inclusive semileptonic decay widths Γ(Λc+→Xe+νe)/Γ¯(D→Xe+νe)=1.28…

Amplitude analysis and branching-fraction measurement of \boldmath $D_{s}^{+} \to K^0_{S}\pi^{+}\pi^{0}$

2021

Utilizing a data set corresponding to an integrated luminosity of 6.32~$\rm fb^{-1}$, recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, we perform an amplitude analysis of the decay $D_{s}^{+} \to K_{S}^{0}\pi^{+}\pi^{0}$ and determine the relative fractions and phase differences of different intermediate processes, which include $K_{S}^{0}\rho(770)^{+}$, $K_{S}^{0}\rho(1450)^{+}$, $K^{*}(892)^{0}\pi^{+}$, $K^{*}(892)^{+}\pi^{0}$, and $K^{*}(1410)^{0}\pi^{+}$. Using a double-tag technique, and making an efficiency correction that relies on our knowledge of the phase-space distribution of the decays coming from the amplitude analysis, the absolute branch…

Precise Measurement of the e(+)e(-) -&gt;pi(+)pi(-) J/psi Cross Section at Center-of-Mass Energies from 3.77 to 4.60 GeV

2017

The cross section for the process e(+)e(-)-&gt; pi(+) pi(-) J/psi is measured precisely at center-of-mass energies from 3.77 to 4.60 GeV using 9 fb(-1) of data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in a fit to the cross section. The first resonance has a mass of (222.0 +/- 3.1 +/- 1.4) MeV/ c(2) and a width of (44.1 +/- 4.3 +/- 2.0)MeV, while the second one has a mass of (4320.0 +/- 10.4 +/- 7.0)MeV/c(2) and a width of (101.4(- 19.7)(+25.3) +/- 10.2) MeV, where the first errors are statistical and second ones are systematic. The first resonance agrees with the Y(4260) resonance reported by previous experiments. The prec…

Observation of the Leptonic Decay $D^+ → τ^+ ν_τ$

2019

Physical review letters 123(21), 211802 (2019). doi:10.1103/PhysRevLett.123.211802

Study of $\psi(3686)\rightarrow\Lambda\bar{\Lambda}\omega$

2022

Based on a data sample of $(448.1\pm2.9)\times10^6$ $\psi(3686)$ events collected with the BESIII detector at the BEPCII collider, the branching fraction of $\psi(3686)\rightarrow\Lambda\bar{\Lambda}\omega$ is measured to be $\rm (3.30\pm0.34(stat.)\pm0.29(syst.))\times10^{-5}$ for the first time. In addition, the $\Lambda\omega$ (or $\bar{\Lambda}\omega$) invariant mass spectra is studied and the potential presence of excited $\Lambda$ states has been investigated.

An improved limit for Γ e e of X ( 3872 ) and Γ e e measurement of ψ ( 3686 )

2015

First simultaneous measurement of $\Xi^0$ and $\bar{\Xi}^0$ asymmetry parameters in $\psi(3686)$ decay

2023

The $\Xi^0$ asymmetry parameters are measured using entangled quantum $\Xi^0$-$\bar{\Xi}^0$ pairs from a sample of $(448.1 \pm 2.9) \times 10^6$ $\psi(3686)$ events collected with the BESIII detector at BEPCII. The relative phase between the transition amplitudes of the $\Xi^0 \bar{\Xi}^0$ helicity states is measured to be $\Delta \Phi = -0.050 \pm 0.150 \pm 0.020$~rad, which implies that there is no obvious polarization at the current level of statistics. The decay parameters of the $\Xi^0$ hyperon $(\alpha_{\Xi^0}, \alpha_{\bar{\Xi}^0}, \phi_{\Xi^0}, \phi_{\bar{\Xi}^0})$ and the angular distribution parameter $(\alpha_{\psi(3686)})$ and $\Delta \Phi$ are measured simultaneously for the fi…

Measurement of the doubly Cabibbo-suppressed decay $D^+\to K^+��^+��^-��^0$ with semileptonic tags

2021

Using an $e^+e^-$ annihilation data sample corresponding to an integrated luminosity of $2.93\,\rm fb^{-1}$ collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the doubly Cabibbo-suppressed decay $D^+\to K^+��^+��^-��^0$ is studied with a semileptonic tag method. After removing the decays containing narrow intermediate resonances, $D^+\to K^+��$, $D^+\to K^+��$, and $D^+\to K^+��$, the branching fraction for the decay $D^+\to K^+��^+��^-��^0$ is determined to be $(1.03 \pm 0.12_{\rm stat} \pm 0.06_{\rm syst})\times 10^{-3}$. The ratio of the branching fraction for $D^+\to K^+��^+��^-��^0$ to its Cabibbo-favored counterpart $D^+\to K^-��^+��^+��^0$ is measured to be $…

Measurement of the Dynamics of the Decays Ds+→η(′)e+νe

2019

PubMed ID: 30978074

Evidence of a Resonant Structure in the Cross Section between 4.05 and 4.60 GeV

2019

The cross section of the process e^{+}e^{-}→π^{+}D^{0}D^{*-} for center-of-mass energies from 4.05 to 4.60 GeV is measured precisely using data samples collected with the BESIII detector operating at the BEPCII storage ring. Two enhancements are clearly visible in the cross section around 4.23 and 4.40 GeV. Using several models to describe the dressed cross section yields stable parameters for the first enhancement, which has a mass of 4228.6±4.1±6.3  MeV/c^{2} and a width of 77.0±6.8±6.3  MeV, where the first uncertainties are statistical and the second ones are systematic. Our resonant mass is consistent with previous observations of the Y(4220) state and the theoretical prediction of a D…

Cross section measurement of e+e−→π+π−ψ(3686) from s=4.0076  GeV to 4.6984 GeV

2021

Observation of the Singly Cabibbo-Suppressed Decay $Λ_{c}^{+} \to nπ^{+}$

2022

The singly Cabibbo-suppressed decay $Λ_{c}^{+} \to nπ^{+}$ is observed for the first time with a statistical significance of $7.3σ$ by using 3.9 $\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ collision data collected at center-of-mass energies between 4.612 and 4.699 GeV with the BESIII detector at BEPCII. The branching fraction of $Λ_{c}^{+} \to nπ^{+}$ is measured to be $(6.6\pm1.2_{\rm stat}\pm0.4_{\rm syst})\times 10^{-4}$. By taking the upper limit of branching fractions of $Λ_{c}^{+} \to pπ^0$ from the Belle experiment, the ratio of branching fractions between $Λ_{c}^{+} \to nπ^{+}$ and $Λ_{c}^{+} \to pπ^0$ is calculated to be larger than 7.2 at the 90% confidence level, which disagrees with the …

Measurement of Proton Electromagnetic Form Factors in e+e−→pp¯ in the Energy Region 2.00–3.08 GeV

2020

The process of e+e−→pp¯ is studied at 22 center-of-mass energy points (s) from 2.00 to 3.08 GeV, exploiting 688.5 pb−1 of data collected with the BESIII detector operating at the BEPCII collider. The Born cross section (σpp¯) of e+e−→pp¯ is measured with the energy-scan technique and it is found to be consistent with previously published data, but with much improved accuracy. In addition, the electromagnetic form-factor ratio (|GE/GM|) and the value of the effective (|Geff|), electric (|GE|), and magnetic (|GM|) form factors are measured by studying the helicity angle of the proton at 16 center-of-mass energy points. |GE/GM| and |GM| are determined with high accuracy, providing uncertaintie…

Improved measurement of the branching fractions of the inclusive decays $D^+ \to K_S^0X $ and $D^0 \to K_S^0X $

2023

By analyzing 2.93 fb$^{-1}$ of $e^+e^-$ collision data taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, the branching fractions of the inclusive decays $D^+\to K^0_S X$ and $D^0\to K^0_S X$ are measured to be $(32.78\pm 0.13\pm 0.27)\%$ and $(20.54\pm 0.12\pm 0.18)\%$, respectively, where the first uncertainties are statistical and the second are systematic. These results are consistent with the world averages of previous measurements, but with improved precision.

Amplitude analysis and branching-fraction measurement of \boldmath $D_{s}^{+} \to K^0_{S}��^{+}��^{0}$

2021

Utilizing a data set corresponding to an integrated luminosity of 6.32~$\rm fb^{-1}$, recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, we perform an amplitude analysis of the decay $D_{s}^{+} \to K_{S}^{0}��^{+}��^{0}$ and determine the relative fractions and phase differences of different intermediate processes, which include $K_{S}^{0}��(770)^{+}$, $K_{S}^{0}��(1450)^{+}$, $K^{*}(892)^{0}��^{+}$, $K^{*}(892)^{+}��^{0}$, and $K^{*}(1410)^{0}��^{+}$. Using a double-tag technique, and making an efficiency correction that relies on our knowledge of the phase-space distribution of the decays coming from the amplitude analysis, the absolute branching fract…

First Observation of the Direct Production of the χ_{c1} in e^{+}e^{-} Annihilation.

2022

Physical review letters 129(12), 122001 (2022). doi:10.1103/PhysRevLett.129.122001

Study of the Decay D+s → π+π+π−η and Observation of the W-annihilation Decay D+s → a0(980)+ρ0

2021

Study of Open-Charm Decays and Radiative Transitions of the X(3872)

2020

The processes X(3872)→D*0D¯0+c.c.,γJ/ψ,γψ(2S), and γD+D− are searched for in a 9.0 fb−1 data sample collected at center-of-mass energies between 4.178 and 4.278 GeV with the BESIII detector. We observe X(3872)→D*0D0¯+c.c. and find evidence for X(3872)→γJ/ψ with statistical significances of 7.4σ and 3.5σ, respectively. No evident signals for X(3872)→γψ(2S) and γD+D− are found, and the upper limit on the relative branching ratio Rγψ≡{B[X(3872)→γψ(2S)]}/{B[X(3872)→γJ/ψ]}&lt;0.59 is set at 90% confidence level. Measurements of branching ratios relative to decay X(3872)→π+π−J/ψ are also reported for decays X(3872)→D*0D0¯+c.c.,γψ(2S),γJ/ψ, and γD+D−, as well as the non-D*0D0¯ three-body decays π0…

An experimental study of γγ → hadrons at LEP

1993

An analysis of γγ interactions has been performed using untagged hadronic data obtained by the ALEPH detector at LEP. The data show at low transverse momentum (pt) are well reproduced by a model based on the vector meson dominance mechinism (VDM). At high pt thrust the presence of hard scattering processes is demonstrated. This component is well described in shape and normalization by a QCD calculation.

Measurement of the absolute branching fractions for purely leptonic D+s decays

2021

We report new measurements of the branching fraction $\cal B(D_s^+\to \ell^+\nu)$, where $\ell^+$ is either $\mu^+$ or $\tau^+(\to\pi^+\bar{\nu}_\tau)$, based on $6.32$ fb$^{-1}$ of electron-positron annihilation data collected by the BESIII experiment at six center-of-mass energy points between $4.178$ and $4.226$ GeV. Simultaneously floating the $D_s^+\to\mu^+\nu_\mu$ and $D_s^+\to\tau^+\nu_\tau$ components yields $\cal B(D_s^+\to \tau^+\nu_\tau) = (5.21\pm0.25\pm0.17)\times10^{-2}$, $\cal B(D_s^+\to \mu^+\nu_\mu) = (5.35\pm0.13\pm0.16)\times10^{-3}$, and the ratio of decay widths $R=\frac{\Gamma(D_s^+\to \tau^+\nu_\tau)}{\Gamma(D_s^+\to \mu^+\nu_\mu)} = 9.73^{+0.61}_{-0.58}\pm 0.36$, whe…

Measurement of the $e^{+}e^{-}\rightarrow����^{0}��^{0}$ cross section at center-of-mass energies from 2.0 to 3.08 GeV

2021

The cross section of the process $e^{+}e^{-}\rightarrow����^{0}��^{0}$ is measured at nineteen center-of-mass energies from 2.0 to 3.08 GeV using data collected with the BESIII detector at the BEPCII storage ring. A resonant structure around 2.20 GeV is observed with significance larger than 5$��$. Using a coherent fit to the cross section line shape, the mass and width are determined to be $M=2223\pm16\pm11~{\rm MeV}/c^2$ and $\varGamma=51\pm29\pm21~{\rm MeV}$, respectively, where the first uncertainties are statistical and the second ones are systematic.

Observation of $e^{+}e^{-}\rightarrow\eta\psi(2S)$ at center-of-mass energies from 4.236 to 4.600 GeV

2021

Using a total of $5.25~{\rm fb}^{-1}$ of $e^{+}e^{-}$ collision data with center-of-mass energies from 4.236 to 4.600 GeV, we report the first observation of the process $e^{+}e^{-}\to \eta\psi(2S)$ with a statistical significance of $5\sigma$. The data sets were collected by the BESIII detector operating at the BEPCII storage ring. We measure the yield of events integrated over center-of-mass energies and also present the energy dependence of the measured cross section.

Measurements of the center-of-mass energies of e+e- collisions at BESIII

2021

Chinese physics / C 45(10), 103001 (2021). doi:10.1088/1674-1137/ac1575

First Observation of the Semileptonic Decay $\Lambda_c^+\rightarrow pK^- e^+\nu_e$

2022

Using $4.5~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data samples collected at the center-of-mass energies ranging from 4.600~GeV to 4.699~GeV with the BESIII detector at the BEPCII collider, a first study of the semileptonic decays $\Lambda_c^+\rightarrow pK^-e^+\nu_e$, $\Lambda_c^+\rightarrow \Lambda(1520) e^+\nu_e$ and $\Lambda_c^+\rightarrow \Lambda(1405) e^+\nu_e$ is performed. The $\Lambda_c^+\rightarrow pK^-e^+\nu_e$ decay is observed with a significance of $8.2\sigma$ and the branching fraction is measured to be $\mathcal{B}(\Lambda_c^+\rightarrow pK^- e^+\nu_e)=(0.88\pm0.17_{\rm stat.}\pm0.07_{\rm syst.})\times 10^{-3}$. We also report evidence of $\Lambda_c^+\rightarrow \Lambda(1…

Measurement of the absolute branching fraction of inclusive semielectronic $D_s^+$ decays

2021

We measure the inclusive semielectronic decay branching fraction of the $D_s^+$ meson. A double-tag technique is applied to $e^+e^-$ annihilation data collected by the BESIII experiment at the BEPCII collider, operating in the center-of-mass energy range $4.178 - 4.230$ GeV. We select positrons from $D_s^+\rightarrow Xe^{+}\nu_e$ with momenta greater than 200 MeV/$c$, and determine the laboratory momentum spectrum, accounting for the effects of detector efficiency and resolution. The total positron yield and semielectronic branching fraction are determined by extrapolating this spectrum below the momentum cutoff. We measure the $D_s^+$ semielectronic branching fraction to be $\mathcal{B}\le…

Measurement of the Absolute Branching Fraction of the Inclusive Decay Λc+ → Λ+X

2018

Physical review letters 121(6), 062003 (2018). doi:10.1103/PhysRevLett.121.062003

A precise measurement of ΓZ→bb/ΓZ→hadrons

1993

A measurement of the partial width ratio Γbb/Γhad using a method which tags the Z --> bb decays through the lif etime of the produced heavy hadrons is presented. This method relies on the tracking precision afforded by a double-sided silicon vertex detector. The tag algorithm makes a probabilistic interpretation of three-dimensional track impact parameters, using the data to measure the resolution. By tagging the two b hadrons separately, both Γbb/Γhad and the tag efficiency can be determined from the data. For a 26% efficiency of tagging a single b hadron within the vertex detector solid angle coverage, a purity of 96% is achieved. A value of Γbb/Γhad = 0.2192+/-0.0026(stat.)+/-0.0016(Γcc/…

Search for the rare semi-leptonic decay $J/\psi\to D^{-}e^{+}\nu_{e}+c.c.$

2021

Using $10.1\times10^{9}$ $J/\psi$ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $\sqrt{s}=3.097~\rm{GeV}$ and collected with the BESIII detector, we present a search for the rare semi-leptonic decay $J/\psi\to D^{-}e^{+}\nu_{e}+c.c.$. No excess of signal above background is observed, and an upper limit on the branching fraction $\mathcal{B}(J/\psi\to D^{-}e^{+}\nu_{e}+c.c.)<7.1\times10^{-8}$ is obtained at $90\%$ confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.

Precision Measurement of the Decay $\Sigma^{+} \rightarrow p\gamma$ in the Process $J/\psi\rightarrow \Sigma^{+}\bar{\Sigma}^{-}$

2023

Using $(10\:087\pm44)\times10^{6}$ $J/\psi$ events collected with the BESIII detector, the radiative hyperon decay $\Sigma\rightarrow p\gamma$ is studied at an electron-positron collider experiment for the first time. The absolute branching fraction is measured to be $\left(0.996 \pm 0.021_{\rm stat.}\pm 0.018_{\rm syst.}\right)\times 10^{-3}$, which is lower than its world average value by $4.2$ standard deviations. Its decay asymmetry parameter is determined to be $-0.652 \pm 0.056_{\rm stat.}\pm 0.020_{\rm syst.}$. The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by $78\%$ and $34\%$, respectively.

Search for sleptons in e+e− collisions at centre-of-mass energies of 161 GeV and 172 GeV

1997

The data recorded by the ALEPH experiment at LEP at centre-of-mass energies of 161 GeV and 172 GeV were analysed to search for sleptons, the supersymmetric partners of leptons. No evidence for the production of these particles was found. The number of candidates observed is consistent with the background expected from four-fermion processes and gammagamma-interactions. Improved mass limits at 95% C.L. are reported.

Amplitude analysis and branching-fraction measurement of Ds+ → KS0 K-π+π+

2021

Study of e+e−→π0X(3872)γ and search for Zc(4020)0→X(3872)γ

2021

Inclusive π±, K± and(p,p¯) differential cross-sections at the Z resonance

1995

Inclusive π±, K± and $$(p,\bar p)$$ differential cross-sections in hadronic decays of the Z have been measured as a function ofz=P hadron/P beam, the scaled momentum. The results are based on approximately 520 000 events measured by the ALEPH detector at LEP during 1992. Charged particles are identified by their rate of ionization energy loss in the ALEPH Time Projection Chamber. The position, ξ*, of the peak in the ln(1/z) distribution is determined, and the evolution of the peak position with centre-of-mass energy is compared with the prediction of QCD.

Measurements of absolute hadronic branching fractions of the Λc+ baryon

2016

Kolcu, Onur Buğra (Arel Author) --- Makale 69 yazarlıdır.

Dark photon search in the mass range between 1.5 and 3.4 GeV/c2

2017

Physics letters / B 774, 252 - 257 (2017). doi:10.1016/j.physletb.2017.09.067

Observation of $e^+e^-\toπ^0π^0ψ_2(3823)$

2022

Using a data sample corresponding to an integrated luminosity of 11.3 $\rm fb^{-1}$ collected at center-of-mass energies from $4.23$ to $4.70$~GeV with the BESIII detector, we observe the process $e^+e^-\toπ^0π^0ψ_2(3823)$ for the first time with a statistical significance of $6.0σ$. The ratio of average cross sections for $e^+e^-\toπ^0π^0ψ_2(3823)$ over $π^+π^-ψ_2(3823)$ is determined to be $\mathcal{R}=\frac{σ[e^+e^-\toπ^0π^0ψ_2(3823)]}{σ[e^+e^-\toπ^+π^-ψ_2(3823)]}=0.57\pm 0.14\pm0.05$, which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the $ψ_2(3823)$ is measured to be $M[ψ_2(3823…

Determination of Spin-parity Quantum Numbers for the Narrow Structure Near the $p\bar{\Lambda}$ Threshold in $e^+e^-\to pK^-\bar{\Lambda}+c.c.$

2023

A narrow structure in the $p\bar{\Lambda}$ system near the mass threshold, named as $X(2085)$, is observed in the process $e^+e^- \to p K^-\bar{\Lambda}$ with a statistical significance greater than $20\sigma$. Its spin and parity are determined for the first time to be $J^P=1^+$ in an amplitude analysis, with statistical significance greater than $5\sigma$ over other quantum numbers. The pole positions of $X(2085)$ are measured to be $M_{\rm pole}=(2086\pm4\pm6)$~MeV and $\Gamma_{\rm pole}=(56\pm5\pm16)$ MeV, where the first uncertainties are statistical and the second ones are systematic. The analysis is based on the study of the process $e^+e^-\to pK^-\bar{\Lambda}$ and uses the data sam…

Measurement of e+e−→γχc0,c1,c2 cross sections at center-of-mass energies between 3.77 and 4.60 GeV

2021

Observation of a cross-section enhancement near mass threshold in e + e - → Λ Λ

2018

The process e(+)e(-) -> Lambda(Lambda) over bar is studied using data samples at root s = 2.2324, 2.400, 2.800 and 3.080 GeV collected with the BESIII detector operating at the BEPCII collider. The Born cross section is measured at root s = 2.2324 GeV, which is 1.0 MeVabove the Lambda(Lambda) over bar mass threshold, to be 305 +/- 45(-36)(+66) pb, where the first uncertainty is statistical and the second systematic. The cross section near threshold is larger than that expected from theory, which predicts the cross section to vanish at threshold. The Born cross sections at root s = 2.400, 2.800 and 3.080 GeV are measured and found to be consistent with previous experimental results, but with…

Measurements of the branching fractions of ψ(3686)→Σ¯0Λ+c.c. and χcJ(J=0,1,2)→ΛΛ¯

2021

Study of the $f_{0}(980)$ through the decay $D_{s}^{+} \to \pi^{+} \pi^{-} e^{+} \nu_{e}$

2023

Using $e^+e^-$ collision data corresponding to an integrated luminosity of 7.33 ${\rm fb^{-1}}$ recorded by the BESIII detector at center-of-mass energies between 4.128 and 4.226 ${\rm GeV}$, we present an analysis of the decay $D_{s}^{+} \to f_{0}(980)e^{+}\nu_{e}$ with $f_{0}(980) \to \pi^{+}\pi^{-}$, where the $D_s^+$ is produced via the process $e^+e^- \to D_{s}^{*\pm}D_{s}^{\mp}$. We observe the $f_{0}(980)$ in the $\pi^+\pi^-$ system and the branching fraction of the decay $D_{s}^{+} \to f_{0}(980)e^{+}\nu_{e}$ with $f_0(980)\to\pi^+\pi^-$ is measured to be $(1.72 \pm 0.13_{\rm stat} \pm 0.10_{\rm syst}) \times10^{-3}$, where the uncertainties are statistical and systematic, respectiv…

Measurement of the branching fraction of $D_s^+\to \tau^+ \nu_{\tau}$ via $\tau^+ \to \mu^+ \nu_{\mu}\bar{\nu_{\tau}}$

2023

Utilizing $7.33~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data taken at the center-of-mass energies of 4.128, 4.157, 4.178, 4.189, 4.199, 4.209, 4.219, and 4.226 GeV with the BESIII detector, the branching fraction of the leptonic decay $D_s^+\to\tau^+\nu_\tau$ via $\tau^+\to\mu^+\nu_\mu\bar \nu_\tau$ is measured to be $\mathcal{B}_{D_s^+\to\tau^+\nu_\tau}=(5.34\pm0.16_{\rm stat}\pm0.10_{\rm syst})\%$. Combining this branching fraction with the world averages of the measurements of the masses of $\tau^+$ and $D_s^+$ as well as the lifetime of $D_s^+$, we extract the product of the decay constant of $D_s^+$ and the $c\to s$ Cabibbo-Kobayashi-Maskawa matrix element to be $f_{D_s^+}|V_{cs}|=(246…

Measurement of in oscillation using quantum correlations in at

2015

We report a measurement of the parameter y(CP) in D-0-(D) over bar (0) oscillations performed by taking advantage of quantum coherence between pairs of D-0(D) over bar (0) mesons produced in e(+)e(-) annihilations near threshold. In this work, doubly-tagged D-0(D) over bar (0) events, where one D decays to a CP eigenstate and the other D decays in a semileptonic mode, are reconstructed using a data sample of 2.92 fb(-1) collected with the BESIII detector at the center-of-mass energy of root s = 3.773 GeV. We obtain y(CP) = (-2.0 +/- 1.3 +/- 0.7)%, where the first uncertainty is statistical and the second is systematic. This result is compatible with the current world average.

Measurement of the doubly Cabibbo-suppressed decay D+→K+π+π−π0 with semileptonic tags

2021

Measurement of the branching fraction of leptonic decay Ds+ →τ+ντ via τ+ →π+π0 ν ¯ τ

2021

Search for the decay Ds+→a0(980)0e+νe

2021

Using 6.32 fb−1 of electron-positron collision data recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, we present the first search for the decay Ds+→a0(980)0e+νe, a0(980)0→π0η, which could proceed via a0(980)−f0(980) mixing. No significant signal is observed. An upper limit of 1.2×10−4 at the 90% confidence level is set on the product of the branching fractions of Ds+→a0(980)0e+νe and a0(980)0→π0η decays.

Precision measurement of the K S meson lifetime with the KLOE detector

2010

Using a large sample of pure, slow, short lived K0 mesons collected with KLOE detector at DaFne, we have measured the KS lifetime. From a fit to the proper time distribution we find tau = (89.562 +- 0.029_stat +- 0.043_syst) ps. This is the most precise measurement today in good agreement with the world average derived from previous measurements. We observe no dependence of the lifetime on the direction of the Ks.

Measurement of the absolute branching fraction of the singly Cabibbo suppressed decay Λc+ →pη′

2022

Physical review / D 106(7), 072002 (2022). doi:10.1103/PhysRevD.106.072002

New Features in the Electromagnetic Structure of the Neutron

2021

Here we present new results for the Born cross section and the effective form factor of the neutron at the center-of-mass energies ${\bf \sqrt{s}}$ between 2.0 and 3.08 GeV, using 18 data sets corresponding to an integrated luminosity of 647.9 pb${\bf ^{-1}}$ from e${\bf ^+}$e${\bf ^-}$ annihilation reactions collected at the BESIII experiment. The process $e^{+}e^{-}\to n\bar{n}$ is analyzed with three individual categories to improve the efficiency of $n\bar{n}$ reconstruction. The cross section of $e^{+}e^{-}\to n\bar{n}$ is measured at 18 c.m. energies where the best precision is 8.1\% at $\sqrt{s}=2.396$ GeV. The corresponding effective form factors are extracted under the assumption $…

Measurements of Differential Cross Sections of Inclusive $\pi^0$ and $K^0_S$ Production in $e^{+}e^{-}$ Annihilation at Energies from 2.2324 to 3.671…

2022

Based on electron positron collision data collected with the BESIII detector operating at the BEPCII storage rings, the differential cross sections of inclusive $\pi^0$ and $K^0_S$ production as a function of hadron momentum, normalized by the total cross section of the $e^{+}e^{-} \to$ hadrons process, are measured at six center-of-mass energies from 2.2324 to 3.6710 GeV. Our results with a relative hadron energy coverage from 0.1 to 0.9 significantly deviate from several theoretical calculations based on existing fragmentation functions, especially at lower energies.

Measurement of the $e^{+}e^{-}\rightarrow\Lambda\bar{\Lambda}$ cross section from threshold to 3.00 GeV using events with initial-state radiation

2023

Using initial-state radiation events from a total integrated luminosity of 11.957 fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at BEPCII, the cross section for the process $e^{+}e^{-}\rightarrow\Lambda\bar{\Lambda}$ is measured in 16 $\Lambda\bar{\Lambda}$ invariant mass intervals from the production threshold up to 3.00 GeV$/c^{2}$. The results are consistent with previous results from BaBar and BESIII, but with better precision and with narrower $\Lambda\bar{\Lambda}$ invariant mass intervals than BaBar.

Measurement of the branching fraction and decay asymmetry of $Λ\to nγ$

2022

The radiative hyperon decay $Λ\to nγ$ is studied using $(10087\pm44)\times 10^6$ $J/ψ$ events collected with the BESIII detector operating at BEPCII. The absolute branching fraction of the decay $Λ\to nγ$ is determined with a significance of 5.6$σ$ to be $[0.832\pm0.038(\rm stat.)\pm0.054(\rm syst.)]\times10^{-3}$, which lies significantly below the current PDG value. By analyzing the joint angular distribution of the decay products, the first determination of the decay asymmetry $α_γ$ is reported with a value of $-0.16\pm0.10(\rm stat.)\pm0.05(\rm syst.)$.

Observation of the Singly Cabibbo Suppressed Decay Λc+→nπ+

2022

Physical review letters 128(14), 142001 (2022). doi:10.1103/PhysRevLett.128.142001

Search for new decay modes of the $\psi_2(3823)$ and the process $e^+e^-\rightarrow\pi^0\pi^0\psi_2(3823)$

2021

The decays $\psi_2(3823)\rightarrow\gamma\chi_{c0,1,2}, \pi^+\pi^-J/\psi, \pi^0\pi^0J/\psi, \eta J/\psi$, and $\pi^0J/\psi$ are searched for using the reaction $e^+e^-\rightarrow\pi^+\pi^-\psi_2(3823)$ in a 19 fb$^{-1}$ data sample collected at center-of-mass energies between 4.1 and 4.7 GeV with the BESIII detector. The process $\psi_2(3823)\rightarrow\gamma\chi_{c1}$ is observed in a 9 fb$^{-1}$ data sample in the center-of-mass energy range 4.3 to 4.7 GeV, which confirms a previous observation but with a higher significance of $11.8\sigma$, and evidence for $\psi_2(3823)\rightarrow\gamma\chi_{c2}$ is found with a significance of $3.2\sigma$ for the first time. The branching-fraction rati…

Search for hyperon $ΔS=ΔQ$ violating decay $Ξ^{0}\toΣ^{-}e^{+}ν_{e}$

2022

Using a data sample of $(1.0087\pm0.0044)\times10^{10}$ $J/ψ$ decay events collected with the BESIII detector at the center-of-mass energy of $\sqrt{s}=3.097$ GeV, we present a search for the hyperon semileptonic decay $Ξ^{0}\toΣ^{-}e^{+}ν_{e}$ which violates the $ΔS=ΔQ$ rule. No significant signal is observed, and the upper limit on the branching fraction $\mathcal{B}(Ξ^{0}\toΣ^{-}e^{+}ν_{e})$ is determined to be $1.6\times10^{-4}$ at the 90% confidence level. This result improves the previous upper limit result by about one order of magnitude.

Measurement of the absolute branching fraction of the inclusive semileptonic $\Lambda_c^+$ decay

2018

Physical review letters 121(25), 251801 (2018). doi:10.1103/PhysRevLett.121.251801

Observation of $D^0\to K_1(1270)^- e^+\nu_e$

2021

Using 2.93 fb$^{-1}$ of $e^+e^-$ collision data taken with the BESIII detector at a center-of-mass energy of 3.773 $\rm \,GeV$, the observation of the $D^0\to K_1(1270)^- e^+\nu_e$ semileptonic decay is presented. The statistical significance of the decay $D^0\to K_1(1270)^- e^+\nu_e$ is greater than $10\sigma$. The branching fraction of $D^0\to K_1(1270)^- e^+\nu_e$ is measured to be $(1.09\pm0.13^{+0.09}_{-0.16} \pm 0.12)\times10^{-3}$. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of $K_1(1270)^- \rightarrow K^-\pi^+\pi^-$. The fraction of longitudinal polarization in $D^0\to K_1(1270)^- e^+\nu_e$ is det…

Search for the standard model Higgs boson

1993

Using a data sample corresponding to about 1 233 000 hadronic Z decays collected by the ALEPH experiment at LEP, the reaction e+e- --> HZ* has been used to search for the standard model Higgs boson, in association with missing energy when Z* --> nunuBAR, or with a pair of energetic leptons when Z* --> e+e- or mu+mu-. No signal was found and, at the 95% confidence level, m(H) exceeds 58.4 GeV/c2. RI ANTONELLI, ANTONELLA/C-6238-2011; Buttar, Craig/D-3706-2011; Stahl, Achim/E-8846-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; St.Denis, Richard/C-8997-2012; Forti, Francesco/H-3035-2011; Ferrante, Isidoro/F-1017-2012

Observation of a Near-Threshold Structure in the K + Recoil-Mass Spectra in e + e − → K + ( D s − D * 0 + D s * − D 0 )

Search for the decay $D_s^+\to a_0(980)^0e^+\nu_e$

2021

Using 6.32 fb$^{-1}$ of electron-positron collision data recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, we present the first search for the decay $D_s^+\to a_0(980)^0 e^+\nu_e,\,a_0(980)^0\rightarrow \pi^0\eta$, which could proceed via $a_0(980)$-$f_0(980)$ mixing. No significant signal is observed. An upper limit of $1.2 \times 10^{-4}$ at the $90\%$ confidence level is set on the product of the branching fractions of $D_{s}^{+}\to a_0(980)^0 e^+\nu_e$ and $a_0(980)^0\rightarrow \pi^0\eta$ decays.

Observation of an Isoscalar Resonance with Exotic J P C = 1 − + Quantum Numbers in J / ψ → γ η η ′

Measurement of the Cross Section for $e^{+}e^{-}\to$ hadrons at Energies from 2.2324 to 3.6710 GeV

2021

Based on electron-positron collision data collected with the BESIII detector operating at the Beijing Electron Positron Collider II storage rings, the value of $R\equiv\sigma(e^{+}e^{-}\to$hadrons)/$\sigma(e^{+}e^{-}\to\mu^{+}\mu^{-})$ is measured at 14 center-of-mass energies from 2.2324 to 3.6710 GeV. The resulting uncertainties are less than $3.0\%$, and are dominated by systematic uncertainties.

Study of the decay D+→K*(892)+KS0 in D+→K+KS0π0

2021

Limit on the production of a light vector gauge boson in $\phi $ mesondecays with the KLOE detector

2012

We present a new limit on the production of a light dark-force mediator with the KLOE detector at DAPHNE. This boson, called U, has been searched for in the decay phi --> eta U, U --> e+ e-, analyzing the decay eta --> pi0 pi0 pi0 in a data sample of 1.7 fb-1. No structures are observed in the e+e- invariant mass distribution over the background. This search is combined with a previous result obtained from the decay eta --> pi+ pi- pi0, increasing the sensitivity. We set an upper limit at 90% C.L. on the ratio between the U boson coupling constant and the fine structure constant of alpha'/alpha < 1.7x10^-5 for 30<M_U<400 MeV and alpha'/alpha < 8x10^-6 for the sub-region 50<M_U<210 MeV. This…

Search for new decay modes of the ψ2(3823) and the process e+e−→π0π0ψ2(3823)

2021

Search for the semi-leptonic decays $\Lambda_c^+ \to \Lambda \pi^+ \pi^- e^+ \nu_e$ and $\Lambda_c^+ \to p K_S^0 \pi^- e^+ \nu_e$

2023

We search for the semi-leptonic decays $\Lambda_c^+ \to \Lambda \pi^+ \pi^- e^+ \nu_e$ and $\Lambda_c^+ \to p K_S^0 \pi^- e^+ \nu_e$ in a sample of 4.5 $\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected in the center-of-mass energy region between 4.600 GeV and 4.699 GeV by the BESIII detector at the BEPCII. No significant signals are observed, and the upper limits on the decay branching fractions are set to be $\mathcal{B}(\Lambda_c^+ \to \Lambda \pi^+ \pi^- e^+ \nu_e)<3.9\times10^{-4}$ and $\mathcal{B}(\Lambda_c^+ \to p K_S^0 \pi^- e^+ \nu_e)<3.3\times10^{-4}$ at the 90% confidence level, respectively.

Study of the decay D s + → K S 0 K S 0 π + and observation of an isovector partner to f 0 ( 1710 )

Observation of the decay $\chi_{cJ} \to \Omega^- \bar{\Omega}^+$

2023

Using an $e^+e^-$ collision data sample of $(27.08 \pm 0.14) \times 10^{8}$ $\psi(3686)$ events collected by the BESIII detector, we report the first observation of $\chi_{cJ} \to \Omega^- \bar{\Omega}^+$ ($J=0,\,1,\,2$) decays with significances of $5.6\sigma$, $6.4\sigma$, and $18\sigma$, respectively, where the $\chi_{cJ}$ mesons are produced in the radiative $\psi(3686)$ decays. The branching fractions are determined to be $\mathcal{B}(\chi_{c0} \to \Omega^- \bar{\Omega}^+) = (3.51 \pm 0.54 \pm 0.29) \times 10^{-5}$, $\mathcal{B}(\chi_{c1} \to \Omega^- \bar{\Omega}^+) = (1.49 \pm 0.23 \pm 0.10) \times 10^{-5}$, and $\mathcal{B}(\chi_{c2} \to \Omega^- \bar{\Omega}^+) = (4.52 \pm 0.24 \pm…

Measurements of Born cross sections of e+e−→Ds*+DsJ−+c.c.

2021

Search for the decay $D^{0} \to π^{0} ν\barν$

2021

We present the first experimental search for the rare charm decay $D^{0} \to π^{0} ν\barν$. It is based on an $e^+e^-$ collision sample consisting of $10.6\times10^{6}$ pairs of $D^0\bar{D}^0$ mesons collected by the BESIII detector at $\sqrt{s}$=3.773 GeV, corresponding to an integrated luminosity of 2.93~fb$^{-1}$. A data-driven method is used to ensure the reliability of the background modeling. No significant $D^{0} \to π^{0} ν\barν$ signal is observed in data and an upper limit of the branching fraction is set to be $2.1\times 10^{-4}$ at the 90$\%$ confidence level. This is the first experimental constraint on charmed-hadron decays into dineutrino final states.

Search for the decay D0 → π0ν¯v

2022

We present the first experimental search for the rare charm decay D0→π0νν¯. It is based on an e+e− collision sample consisting of 10.6×106 pairs of D0D¯0 mesons collected by the BESIII detector at s=3.773 GeV, corresponding to an integrated luminosity of 2.93 fb−1. A data-driven method is used to ensure the reliability of the background modeling. No significant D0→π0νν¯ signal is observed in data and an upper limit of the branching fraction is set to be 2.1×10−4 at the 90% confidence level. This is the first experimental constraint on charmed-hadron decays into dineutrino final states.

Observation of an Isoscalar Resonance with Exotic $J^{P C} = 1^{− +}$ Quantum Numbers in $J / ψ → γ η η ′$

2022

Physical review letters 129(19), 192002 (2022). doi:10.1103/PhysRevLett.129.192002

Measurement of the phase between strong and electromagnetic amplitudes of J/ψ decays

2019

Kolcu, Onur Buğra (Arel Author)

Measurement of the Cross Section for e+e−→Ξ−Ξ¯+ and Observation of an Excited Ξ Baryon

2020

Using a total of 11.0 fb−1 of e+e− collision data with center-of-mass energies between 4.009 and 4.6 GeV and collected with the BESIII detector at BEPCII, we measure fifteen exclusive cross sections and effective form factors for the process e+e−→Ξ−Ξ¯+ by means of a single baryon-tag method. After performing a fit to the dressed cross section of e+e−→Ξ−Ξ¯+, no significant ψ(4230) or ψ(4260) resonance is observed in the Ξ−Ξ¯+ final states, and upper limits at the 90% confidence level on ΓeeB for the processes ψ(4230)/ψ(4260)→Ξ−Ξ¯+ are determined. In addition, an excited Ξ baryon at 1820 MeV/c2 is observed with a statistical significance of 6.2–6.5σ by including the systematic uncertainty, an…

Precision measurement of the matrix elements for $\eta\to\pi^+\pi^-\pi^0$ and $\eta\to\pi^0\pi^0\pi^0$ decays

2023

A precision measurement of the matrix elements for $\eta\to\pi^+\pi^-\pi^0$ and $\eta\to\pi^0\pi^0\pi^0$ decays is performed using a sample of $(10087\pm44)\times10^6$ $J/\psi$ decays collected with the BESIII detector. The decay $J/\psi \to \gamma \eta$ is used to select clean samples of 631,686 $\eta\to\pi^+\pi^-\pi^0$ decays and 272,322 $\eta\to\pi^0\pi^0\pi^0$ decays. The matrix elements for both channels are in reasonable agreement with previous measurements. The non-zero $gX^2Y$ term for the decay mode $\eta\to\pi^+\pi^-\pi^0$ is confirmed, as reported by the KLOE Collaboration, while the other higher-order terms are found to be insignificant. Dalitz plot asymmetries in the $\eta\to\p…