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…

Search for an Invisibly Decaying Z′ Boson at Belle II in e+e−→μ+μ−(e±μ∓) Plus Missing Energy Final States

2020

Theories beyond the standard model often predict the existence of an additional neutral boson, the Z′. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a Z′ in the process e+e-→μ+μ-Z′ and of a lepton-flavor-violating Z′ in e+e-→e±μZ′. We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an Lμ-Lτ theory, into upper limits on the Z′ coupling constant at the level of 5×10-2-1 for MZ′≤6 GeV/c2.

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.

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 ...

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

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

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$)^\circ$…

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…

First Evidence for cos2β>0 and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity

2018

We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] p…

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

2019

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

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

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.

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

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…

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…

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.

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]}<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…

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

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…

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

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.

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

Proton Shell Evolution below Sn132 : First Measurement of Low-Lying β -Emitting Isomers in Ag123,125

2019

The β-delayed γ-ray spectroscopy of neutron-rich 123;125Ag isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN and the long-predicted 1/2¯ β-emitting isomers in 123;125Ag are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest 9/2+ and 1/2¯ levels is extended in Ag isotopes up to N = 78, providing a clear signal for the reduction of the Z = 40 subshell gap in Ag towards N = 82. Shellmodel calculations with the state-of-the-art VMU plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in 123;125Ag. The tensor force is found to play a crucial role in the evolution of…

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…

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…

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…

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.

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

2021

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 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.

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)%.

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.

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…

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

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…

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.

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.

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…

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

The Belle II Physics Book

2019

cd. autorów: L. Cao48,‡, G. Caria145,‡, G. Casarosa57,‡, C. Cecchi56,‡,D. Cˇ ervenkov10,‡,M.-C. Chang22,‡, P. Chang92,‡, R. Cheaib146,‡, V. Chekelian83,‡, Y. Chen154,‡, B. G. Cheon28,‡, K. Chilikin77,‡, K. Cho70,‡, J. Choi14,‡, S.-K. Choi27,‡, S. Choudhury35,‡, D. Cinabro170,‡, L. M. Cremaldi146,‡, D. Cuesta47,‡, S. Cunliffe16,‡, N. Dash33,‡, E. de la Cruz Burelo9,‡, E. de Lucia52,‡, G. De Nardo54,‡, †Editor. ‡Belle II Collaborator. §Theory or external contributing author. M. De Nuccio16,‡, G. De Pietro59,‡, A. De Yta Hernandez9,‡, B. Deschamps129,‡, M. Destefanis60,‡, S. Dey116,‡, F.Di Capua54,‡, S.Di Carlo75,‡, J. Dingfelder129,‡, Z. Doležal10,‡, I. Domínguez Jiménez125,‡, T.V. Dong30,26,…

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…

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

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…