0000000001076173
AUTHOR
P. Elmer
Updated measurement of the τ lepton lifetime
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.
Studies of Quantum Chromodynamics with the ALEPH Detector
Previously published and as vet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented.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 forCPTand Lorentz Violation inB0−B¯0Oscillations with Dilepton Events
We report results of a search for CPT and Lorentz violation in B{sup 0}-{bar B}{sup 0} oscillations using inclusive dilepton events from 232 million {Upsilon}(4S) {yields} B{bar B} decays recorded by the BABAR detector at the PEP-II B Factory at SLAC. We find 2.8{sigma} significance, compatible with no signal, for variations in the complex CPT violation parameter z at the Earth's sidereal frequency and extract values for the quantities {Delta}a{sub {mu}} in the general Lorentz-violating standard-model extension. The spectral powers for variations in z over the frequency range 0.26 year{sup -1} to 2.1 day{sup -1} are also compatible with no signal.
Improved tau polarisation measurement
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…
Search for the decayB+→K¯*0(892)K+
We report on a search for the process B+ -> (K) over bar*(0)(892)K+ using 232 X 10(6) Y(4S) -> B (B) over bar B decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. From a signal yield of 25 +/- 13[stat] +/- 7[syst] B+ -> (K) over bar*(0)(892)(-> K-pi(+))K+ events, we place an upper limit on the branching fraction B(B+ -> (K) over bar*(0)(892)K+) of 1.1 X 10(-6), at the 90% confidence level.
Measurement ofCP-violating asymmetries inB0→(ρπ)0decays using a time-dependent Dalitz plot analysis
We report on a measurement of CP-violating asymmetries (A{sub CP}) in the Cabibbo-suppressed D{sup 0} {yields} {pi}{sup +}{pi}{sup -} and D{sup 0} {yields} K{sup +}K{sup -} decays reconstructed in a data sample corresponding to 5.9 fb{sup -1} of integrated luminosity collected by the upgraded Collider Detector at Fermilab. We use the strong decay D*{sup +} {yields} D{sup 0}{pi}{sup +} to identify the flavor of the charmed meson at production and exploit CP-conserving strong c{bar c} pair-production in p{bar p} collisions. High-statistics samples of Cabibbo-favored D{sup 0} {yields} K{sup -}{pi}{sup +} decays with and without a D*{sup {+-}} tag are used to correct for instrumental effects an…
A measurement of the inclusive b → sγ branching ratio
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 …
Study of the CP asymmetry of B0 -> J/psi K0S decays in ALEPH
The decay B0 -> J/psi K0_S is reconstructed with J/psi -> e+ e- or mu+ mu- and K0_S -> pi+ pi-. From the full ALEPH dataset at LEP1 of about 4 million hadronic Z decays, 23 candidates are selected with an estimated purity of 71%. They are used to measure the CP asymmetry of this decay, given by sin 2beta in the Standard Model, with the result sin 2beta = 0.84 +0.82-1.04 +-0.16. This is combined with existing measurements from other experiments, and increases the confidence level that CP violation has been observed in this channel to 98%.
Search for the Bc meson in hadronic Z decays
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…
Measurement of the hadronic form factor inD0→K−e+νedecays
We present a preliminary measurement of the q2 dependence of the D0 --> K- e+ nu_e decay rate. This rate is proportional to the hadronic form factor squared, specified by a single parameter. This is either the mass in the simple pole ansatz m_pole = (1.854 +- 0.016 +- 0.020) GeV/c2 or the scale in the modified pole ansatz alpha_pole = 0.43 +- 0.03 +- 0.04. The first error refers to the statistical, the second to the systematic uncertainty.
Measurement of the W mass in e(+)e(-) collisions at production threshold
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…
Measurement ofcos2βinB0→D(*)h0Decays with a Time-Dependent Dalitz Plot Analysis ofD→Ks0π+π−
We study the time-dependent Dalitz plot of D-->K_{S};{0}pi;{+}pi;{-} in B;{0}-->D;{(*)}h;{0} decays, where h;{0} is a pi;{0}, eta, eta;{'}, or omega meson and D;{*}-->Dpi;{0}, using a data sample of 383x10;{6} Upsilon(4S)-->BB[over ] decays collected with the BABAR detector. We determine cos2beta=0.42+/-0.49+/-0.09+/-0.13, sin2beta=0.29+/-0.34+/-0.03+/-0.05, and |lambda|=1.01+/-0.08+/-0.02, where the first error is statistical, the second is the experimental systematic uncertainty, and the third, where given, is the Dalitz model uncertainty. Assuming the world average value for sin2beta and |lambda|=1, cos2beta>0 is preferred over cos2beta<0 at 86% confidence level.
Scalar quark searches in $e^+ e^-$ collisions at $\sqrt{s}$ = 181-184 GeV
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 DecaysB0→Ds(*)+π−andB0→Ds(*)−K+
We report the observation of decays B-0 -> D-s((*)+)pi(-) and B-0 -> Ds(*)-K+ in a sample of 230x10(6) Upsilon(4S)-> BB events recorded with the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) storage ring. We measure the branching fractions B(B-0 -> D-s(+)pi(-))=(1.3 +/- 0.3(stat)+/- 0.2(syst))x10(-5), B(B-0 -> Ds-K+)=(2.5 +/- 0.4(stat)+/- 0.4(syst))x10(-5), B(B-0 -> D-s(*+)pi(-))=(2.8 +/- 0.6(stat)+/- 0.5(syst))x10(-5), and B(B-0 -> Ds*-K+)=(2.0 +/- 0.5(stat)+/- 0.4(syst))x10(-5). The significances of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is the first observation of B-0 -> D-s(+)pi(-), B-0 -> D-s(*+)pi(-), and B-0 -> D…
Production and decay of Ωc0
We present an analysis of inclusive Omega(c)(0) baryon production and decays in 230.5 fb(-1) of data recorded with the BABAR detector. Omega(c)(0) baryons are reconstructed in four final states (Omega(-)pi(+), Omega(-)pi(+)pi(0), Omega(-)pi(+)pi(+)pi(-), Xi(-)K(-)pi(+)pi(+)) and the corresponding ratios of branching fractions are measured. We also measure the momentum spectrum in the e(+)e(-) center-of-mass frame. From the spectrum, we observe Omega(c)(0) production from B decays and in cc events, and extract the two rates of production.
Search ForT,CP, andCPTViolation inB0−B¯0Mixing with Inclusive Dilepton Events
The authors report the results of a search for T, CP and CPT violation in B{sup 0}-{bar B}{sup 0} mixing using an inclusive dilepton sample collected by the BABAR experiment at the PEP-II B Factory. Using a sample of 232 million B{bar B} pairs, with a simultaneous likelihood fit of the same-sign and opposite-sign dileptons, they measure the T and Cp violation parameter |q/p|-1 = (-0.8 {+-} 2.7(stat.) {+-} 1.9(syst.)) x 10{sup -3}, and the CPT and CP parameters Im z = (-13.9 {+-} 7.3(stat.) {+-} 3.2(syst.)) x 10{sup -3} and {Delta}{Lambda} x Re z = (-7.1 {+-} 3.9(stat.) {+-} 2.0(syst.)) x 10{sup -3} ps{sup -1}. The statistical correlation between the measurements of Im z and {Delta}{Lambda} …
Observation ofCPViolation inB→η′K0Decays
We report observations of CP violation in the decays B0 -> K+pi- and B0 -> pi+pi- in a sample of 383 million Y4S -> BBbar events. We find 4372 +/- 82 B0 -> K+pi- decays and measure the direct CP-violating charge asymmetry Akpi = -0.107 +/- 0.018 (stat) +0.007-0.004 (syst), which excludes the CP-conserving hypothesis with a significance of 5.5 standard deviations. In the same sample we find 1139 +/- 49 B0 -> pi+pi- decays and measure the CP-violating asymmetries Spipi = -0.60 +/- 0.11 (stat) +/- 0.03 (syst) and Cpipi = -0.21 +/- 0.09 (stat) +/- 0.02 (syst). CP conservation in B0 -> pi+pi- (Spipi=Cpipi=0) is excluded at a confidence level 1-C.L. = 8 * 10^{-8}, corresponding to 5.4 standard de…
Measurements of the branching fractions ofB0→K*0K+K−,B0→K*0π+K−,B0→K*0K+π−, andB0→K*0π+π−
Branching fraction measurements of charmless B{sup 0}{yields}K*{sup 0}h{sub 1}{sup +}h{sub 2}{sup -} (h{sub 1,2}=K, {pi}) decays are presented, using a data sample of 383x10{sup 6} {upsilon}(4S){yields}BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. The results are B(B{sup 0}{yields}K*{sup 0}K{sup +}K{sup -})=(27.5{+-}1.3{+-}2.2)x10{sup -6}, B(B{sup 0}{yields}K*{sup 0}{pi}{sup +}K{sup -})=(4.6{+-}1.1{+-}0.8)x10{sup -6}, and B(B{sup 0}{yields}K*{sup 0}{pi}{sup +}{pi}{sup -})=(54.5{+-}2.9{+-}4.3)x10{sup -6}. The first errors quoted are statistical and the second are systematic. An upper limit is set for B(B{sup 0}{yields}K*{sup 0}K{sup +}{p…
Study of theDsJ*(2317)+andDsJ(2460)+mesons in inclusivecc¯production nears=10.6 GeV
A study of the $D_{sJ}^*(2317)^+$ and $D_{sJ}(2460)^+$ mesons in inclusive $c\bar{c}$ production is presented using 232~${\rm fb}^{-1}$ of data collected by the BaBar experiment near $\sqrt{s} = 10.6$~\gev. Final states consisting of a $D_s^+$ meson along with one or more $\pi^0$, $\pi^\pm$, or $\gamma$ particles are considered. Estimates of the mass and limits on the width are provided for both mesons and for the $D_{s1}(2536)^+$ meson. A search is also performed for neutral and doubly-charged partners of the $D_{sJ}^*(2317)^+$ meson.
Search for charginos and neutralinos with R-parity violation at =130 136
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.
Tau leptonic branching ratios
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
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 the Pseudoscalar Decay ConstantfDsUsing Charm-Tagged Events ine+e−Collisions ats=10.58 GeV
Using 230.2 fb^(-1) of e+e- annihilation data collected with the BABAR detector at and near the peak of the Y(4S) resonance, 489 +/- 55 events containing the pure leptonic decay D_s^+ --> mu^+ nu_mu have been isolated in charm-tagged events. The ratio of partial widths Gamma(D_s^+ --> mu^+ nu_mu)/Gamma(D_s^+ --> phi pi^+) is measured to be 0.143 +/- 0.018 +/- 0.006 allowing a determination of the pseudoscalar decay constant f_{D_s} = (283 +/- 17 +/- 7 +/- 14) MeV. The errors are statistical, systematic, and from the D_s^+ --> phi pi^+ branching ratio, respectively.
Study of muon-pair production at centre-of-mass energies from 20 to 136 GeV with the ALEPH detector
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 …
Resonant structure and flavour tagging in the Bπ±system using fully reconstructed B decays
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…
Search for rare quark-annihilation decays, B --> Ds(*) Phi
We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, these decays are expected to be highly suppressed since they proceed through annihilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set Bayesian 90% confidence level upper limits on the branching fractions BF(B- --> Ds- Phi) Ds*- Phi)<1.2x10^(-5). These results are consistent with Standard Model expectations.
Observation ofB0→K*0K¯*0and Search forB0→K*0K*0
We report the observation of the b-->d penguin-dominated decay B;{0}-->K;{*0}K[over ];{*0} with a sample of 383.2+/-4.2 million BB[over ] pairs collected with the BABAR detector at the PEP-II asymmetric-energy e;{+}e;{-} collider at the Stanford Linear Accelerator Center. The measured branching fraction is B(B;{0}-->K;{*0}K[over ];{*0})=[1.28_{-0.30};{+0.35}+/-0.11]x10;{-6} and the fraction of longitudinal polarization is f_{L}(B;{0}-->K;{*0}K[over ];{*0})=0.80_{-0.12};{+0.10}+/-0.06. The first error quoted is statistical and the second systematic. We also obtain an upper limit at the 90% confidence level on the branching fraction for B(B;{0}-->K;{*0}K;{*0})<0.41x10;{-6}.
Measurement of the branching fraction forB±→χc0K±
We present a measurement of the branching fraction of the decay ${B}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\chi}}_{c0}{K}^{\ifmmode\pm\else\textpm\fi{}}$ from a sample of $89\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected by the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. The ${\ensuremath{\chi}}_{c0}$ meson is reconstructed through its two-body decays to ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${K}^{+}{K}^{\ensuremath{-}}.$ We measure $\mathcal{B}{(B}^{\ifmmode\pm\else\textpm\fi{}}\stackrel{\ensuremath{\rightarrow}}{}{\ensuremath{\chi}}_{c0}{K}^{\ifmmode\pm\else\textpm\fi{}})\ifmmode\times\e…
Study of resonances in exclusiveBdecays toD¯(*)D(*)K
We present a study of resonances in exclusive decays of $B$ mesons to $\bar{D}^{(*)} D^{(*)} K$. We report the observation of the decays $B \to \Dbar^{(*)} D^+_{s1}(2536)$ where the $D^+_{s1}(2536)$ is reconstructed in the $D^{*0}K^+$ and $D^{*+} K^0_S$ decay channels. We report also the observation of the decays $B \to \psi(3770) K$ where the $\psi(3770)$ decays to $\Dbar^0 D^0$ and $D^- D^+$. In addition, we present the observation of an enhancement for the $\Dbar^{*0} D^0$ invariant mass in the decays $B \to \Dbar^{*0} D^0 K$, at a mass of $(3875.1 {}^{+0.7}_{-0.5} \pm 0.5)$ MeV/$c^2$ with a width of $(3.0 {}^{+1.9}_{-1.4} \pm 0.9)$ MeV (the first errors are statistical and the second ar…
Observation of the Semileptonic DecaysB→D*τ−ν¯τand Evidence forB→Dτ−ν¯τ
We present measurements of the semileptonic decays B--->D0tau-nutau, B--->D*0tau-nutau, B0-->D+tau-nutau, and B0-->D*+tau-nutau, which are potentially sensitive to non-standard model amplitudes. The data sample comprises 232x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector. From a combined fit to B- and B0 channels, we obtain the branching fractions B(B-->Dtau-nutau)=(0.86+/-0.24+/-0.11+/-0.06)% and B(B-->D*tau-nutau)=(1.62+/-0.31+/-0.10+/-0.05)% (normalized for the B0), where the uncertainties are statistical, systematic, and normalization-mode-related.
A study of single W production in e+e− collisions at –183 GeV
Abstract Single W production is studied in the data recorded with the ALEPH detector at LEP at centre-of-mass energies between 161 and 183 GeV. The cross section is measured to be σW=0.41±0.17(stat.)±0.04(syst.) pb at 183 GeV, consistent with the Standard Model expectation. Limits on non-standard WWγ couplings are deduced as −1.6 γ (λ γ =0) and −1.6 γ (κ γ =1) at 95% C.L. A search for effectively invisible decays of the W boson in W pair production is performed, leading to an upper limit on the branching ratio of 1.3% ( Γ inv =27 MeV ) at 95% C.L.
Four-fermion production in $e^+e^-$ collisions at centre-of-mass energies of 130 and 136 GeV
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
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, …
Measurement of the branching fraction and time-dependentCPasymmetry in the decayB0→D*+D*−Ks0
We study the decay B-0 ->(D*+D*-KS0) using (230 +/- 2)x10(6)B (B) over bar pairs collected by the BABAR detector at the PEP-II B factory. We measure a branching fraction B(B-0 ->(D*+D*-KS0))=(4.4 +/- 0.4 +/- 0.7)x10(-3) and find evidence for the decay B-0 -> D*-Ds1+(2536) with a significance of 4.6 sigma. A time-dependent CP asymmetry analysis is also performed to study the possible resonant contributions to B-0 ->(D*+D*-KS0) and the sign of cos2 beta. Our measurement indicates that there is a sizable resonant contribution to the decay B-0 ->(D*+D*-KS0) from an unknown D-s1(+) state with large width, and that cos2 beta is positive at the 94% confidence level under certain theoretical assump…
Dalitz plot analysis of the decay B±→K±K±K∓
We analyze the three-body charmless decay B-+/-->(KKK -/+)-K-+/--K-+/- using a sample of 226.0 +/- 2.5 million B (B) over bar pairs collected by the BABAR detector. We measure the total branching fraction and CP asymmetry to be B=(35.2 +/- 0.9 +/- 1.6)x10(-6) and A(CP)=(-1.7 +/- 2.6 +/- 1.5)%. We fit the Dalitz plot distribution using an isobar model and measure the magnitudes and phases of the decay coefficients. We find no evidence of CP violation for the individual components of the isobar model. The decay dynamics is dominated by the K+K- S-wave, for which we perform a partial-wave analysis in the region m(K+K-)< 2 GeV/c(2). Significant production of the f(0)(980) resonance, and of a sp…
Study ofe+e−→pp¯via initial-state radiation atBABAR
The e{sup +}e{sup -}{yields}pp cross section is determined over a range of pp masses, from threshold to 4.5 GeV/c{sup 2}, by studying the e{sup +}e{sup -}{yields}pp{gamma} process. The data set corresponds to an integrated luminosity of 232 fb{sup -1}, collected with the BABAR detector at the PEP-II storage ring, at an e{sup +}e{sup -} center-of-mass energy of 10.6 GeV. The mass dependence of the ratio of electric and magnetic form factors, G{sub E}/G{sub M}, is measured for pp masses below 3 GeV/c{sup 2}; its value is found to be significantly larger than 1 for masses up to 2.2 GeV/c{sup 2}. We also measure J/{psi}{yields}pp and {psi}(2S){yields}pp branching fractions and set an upper limi…
Study ofB→D(*)Ds(J)(*)decays and measurement ofDs−andDsJ(2460)−branching fractions
We present branching fraction measurements of twelve B meson decays of the form B --> D^(*)D_s(J)^(*). The results are based on Y(4S) decays in BBbar pairs. One of the B mesons is fully reconstructed and the other decays to two charm mesons, of which one is reconstructed, and the mass and momentum of the other is inferred by kinematics. Combining these results with previous exclusive branching fraction measurements, we determine BR(D_s^- --> phi pi^-) = (4.62 +/- 0.36_stat. +/- 0.51_syst.)%, BR(D_sJ(2460)^- --> D_s^*- pi^0) = (56 +/- 13_stat. +/- 9_syst.)% and BR(D-sJ(2460)^- --> D_s^- gamma) = (16 +/- 4_stat. +/- 3_syst.)%.
Measurement of the Time-DependentCPAsymmetry inB0→DCP(*)h0Decays
We report a measurement of the time-dependent CP-asymmetry parameters S and C in color-suppressed B-0 -> D((*)0)h(0) decays, where h(0) is a pi(0), eta, or omega meson, and the decays to one of the CP eigenstates K+K-, K-S(0)pi(0), or K-S(0)omega. The data sample consists of 383x10(6) Upsilon(4S)-> B (B) over bar decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The results are S=-0.56 +/- 0.23 +/- 0.05 and C=-0.23 +/- 0.16 +/- 0.04, where the first error is statistical and the second is systematic.
Improved measurement of time-dependentCPasymmetries and theCP-odd fraction in the decayB0→D*+D*−
We present an updated measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B0-->D*+D*- using 232x10(6)BB pairs collected by the BABAR detector at the SLAC PEP-II B factory. We determine the CP-odd fraction to be 0.125+/-0.044(stat)+/-0.007(syst). The time-dependent CP asymmetry parameters C+ and S+ are determined to be 0.06+/-0.17(stat)+/-0.03(syst) and -0.75+/-0.25(stat)+/-0.03(syst), respectively. The standard model predicts these parameters to be 0 and -sin2beta, respectively, in the absence of penguin amplitude contributions.
Measurements ofe+e−→K+K−η,K+K−π0, andKs0K±π∓cross sections using initial state radiation events
This paper reports measurements of processes: e+e-→γKS0K±π∓, e+e-→γK+K-π0, e+e-→γϕη, and e+e-→γϕπ0. The initial-state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ≈4.6 GeV. The overall size of the data sample analyzed is 232 fb-1, collected by the BABAR detector running at the PEP-II e+e- storage ring. From the Dalitz plot analysis of the KS0K±π∓ final state, moduli, and relative phase of the isoscalar and the isovector components of the e+e-→KK*(892) cross section are determined. Parameters of ϕ and ρ recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli, and phases…
Observation ofY(3940)→J/ψωinB→J/ψωKatBABAR
We present a study of the decays B;{0,+}-->J/psiomegaK;{0,+} using 383x10;{6} BB[over ] events obtained with the BABAR detector at PEP-II. We observe Y(3940)-->J/psiomega, with mass 3914.6_{-3.4};{+3.8}(stat)+/-2.0(syst) MeV/c;{2}, and width 34_{-8};{+12}(stat)+/-5(syst) MeV. The ratio of B0 and B+ decay to YK is 0.27_{-0.23};{+0.28}(stat)-0.01+0.04(syst), and the relevant B0 and B+ branching fractions are reported.
Observation ofB+→a1+(1260)K0andB0→a1−(1260)K+
We present branching fraction measurements of the decays B(+)-->a(1)(+)(1260)K(0) and B(0)-->a(1)(-)(1260)K(+) with a(1)(+/-)(1260)-->pi(-/+)pi(+/-)pi(+/-). The data sample corresponds to 383 x 10(6) BB pairs produced in e(+)e(-) annihilation through the Upsilon(4S) resonance. We measure the products of the branching fractions B(B(+)-->a(1)(+)(1260)K(0)B(a(1)(+)(1260)-->pi(-)pi(+)pi(+))=(17.4+/-2.5+/-2.2) x 10(-6) and B(B(0)-->a(1)(-)(1260)K(+)B(a(1)(-)(1260)-->pi(+)pi(-)pi(-)) = (8.2+/-1.5+/-1.2) x 10(-6). We also measure the charge asymmetries A(ch)(B(+)-->a(1)(+)(1260)K(0) = 0.12+/-0.11+/-0.02 and A(ch)(B(0)-->a(1)(-)(1260)K+) = -0.16+/-0.12+/-0.01. The first uncertainty quoted is statis…
Study of the exclusive initial-state-radiation production of the D¯¯¯D system
A study of exclusive production of the $D \bar D$ system through initial-state r adiation is performed in a search for charmonium states, where $D=D^0$ or $D^+$. The $D^0$ mesons are reconstructed in the $D^0 \to K^- \pi^+$, $D^0 \to K^- \pi^+ \pi^0$, and $D^0 \to K^- \pi^+ \pi^+ \pi^-$ decay modes. The $D^+$ is reconstructed through the $D^+ \to K^- \pi^+ \pi^+$ decay mode. The analysis makes use of an integrated luminosity of 288.5 fb$^{-1}$ collected by the BaBar experiment. The $D \bar D$ mass spectrum shows a clear $\psi(3770)$ signal. Further structures appear in the 3.9 and 4.1 GeV/$c^2$ regions. No evidence is found for Y(4260) decays to $D \bar D$, implying an up per limit $\frac{\…
Search for B^{+}→τ^{+}ν
We present a search for the decay B + → τ + ν using 383 × 10 6 B ¯¯¯ B pairs collected at the Υ ( 4 S ) resonance with the BABAR detector at the SLAC PEP-II B -Factory. A sample of events with one reconstructed semileptonic B decay ( B − → D 0 ℓ − ¯ ν ℓ X ) is selected, and in the recoil a search for B + → τ + ν is performed. The τ is identified in the following channels: τ + → e + ν ¯ ν , τ + → μ + ν ¯ ν , τ + → π + ¯ ν , and τ + → π + π 0 ¯ ν . We measure a branching fraction of B ( B + → τ + ν ) = ( 0.9 ± 0.6 ( stat . ) ± 0.1 ( syst . ) ) × 10 − 4 . In the absence of a significant signal, we calculate an upper limit at the 90% confidence level of B ( B + → τ + ν ) < 1.7 × 10 − 4 . We cal…
Charm counting in b decays
??? 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 the Rare Decay B→πl+l−
We have performed a search for the flavor-changing neutral-current decays B → π ℓ + ℓ − , where ℓ + ℓ − is either e + e − or μ + μ − , using a sample of 230 × 10 6 Υ ( 4 S ) → B ¯¯¯ B decays collected with the BABAR detector. We observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be B ( B → π ℓ + ℓ − ) < 9.1 × 10 − 8 at 90% confidence level. We also search for the lepton-flavor-violating decays B → π e ± μ ∓ and measure an upper limit on the isospin-averaged branching fraction of B ( B → π e ± μ ∓ ) < 9.2 × 10 − 8 at 90% confidence level.
Study of excited charm-strange baryons with evidence for new baryonsΞc(3055)+andΞc(3123)+
We present a study of excited charm-strange baryon states produced in e{sup +}e{sup -} annihilations at or near a center-of-mass energy of 10.58 GeV, in a data sample with an integrated luminosity of 384 fb{sup -1} recorded with the BABAR detector at the PEP-II e+e storage rings at the Stanford Linear Accelerator Center. We study strong decays of charm-strange baryons to {Lambda}{sub c}{sup +}K{sub S}{sup 0}, {Lambda}{sub c}{sup +}K{sup -}, {Lambda}{sub c}{sup +}K{sup -}{pi}{sup +}, {Lambda}{sub c}{sup +}K{sub S}{sup 0}{pi}{sup -}, {Lambda}{sub c}{sup +}K{sub S}{sup 0}{pi}{sup -}{pi}{sup +}, {Lambda}{sub c}{sup +}K{sup -}{pi}{sup -}{pi}{sup +}. This study confirms the existence of the state…
Test of the flavour independence of αs
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 theB0→π−l+νForm-Factor Shape and Branching Fraction, and Determination of|Vub|with a Loose Neutrino Reconstruction Technique
We report the results of a study of the exclusive charmless semileptonic decay, B-0 ->pi(-)center dot(+)nu, undertaken with approximately 227x10(6) BB pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with an innovative loose neutrino reconstruction technique. We obtain partial branching fractions in 12 bins of q(2), the momentum transfer squared, from which we extract the f(+)(q(2)) form-factor shape and the total branching fraction B(B-0 ->pi(-)l(+)nu)=(1.46 +/- 0.07(stat)+/- 0.08(syst))x10(-4). Based on a recent unquenched lattice QCD calculation of the form factor in the range q(2)> 16 GeV2, we f…
Search for the decaysB0→e+e−γandB0→μ+μ−γ
We present results of a search for the decays $B^0 \to \ell^+\ell^-\gamma$ ($\ell=e$, $\mu$). The search is performed using $320\times 10^{6}$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the BABAR detector at the PEP-II $B$ Factory at SLAC. We find no significant signal and set the following branching fraction upper limits at the 90% confidence level: $\mathcal{B}(B^0\to e^+e^-\gamma)<1.2\times 10^{-7}$ and $\mathcal{B}(B^0\to \mu^+\mu^-\gamma)<1.5\times 10^{-7}$.
Search for the neutral Higgs bosons of the MSSM in e(+)e(-) collisions at root s from 130 to 172 GeV
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…
Search for the rare charmless hadronic decayB+→a0+π0
We present a search for B decays to a charged scalar meson a0+ and a pi0 where the a0+ decays to an eta meson and a pi+. The analysis was performed on a data sample consisting of 383x10-6 BBbar pairs collected with the Babar detector at the PEP-II asymmetric-energy B Factory at SLAC. We find no significant signal and set an upper limit on the product branching fraction BF[(B+ -> a0+ pi0) x (a0+ -> eta pi+)] of 1.4x10-6 at the 90% confidence level.
Measurement of the branching fraction for D0 → K-π+
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
Study ofB0→π0π0,B±→π±π0, andB±→K±π0decays, and isospin analysis ofB→ππdecays
We present updated measurements of the branching fractions and CP asymmetries for B{sup 0}{yields}{pi}{sup 0}{pi}{sup 0}, B{sup {+-}}{yields}{pi}{sup {+-}}{pi}{sup 0}, and B{sup {+-}}{yields}K{sup {+-}}{pi}{sup 0}. Based on a sample of 383x10{sup 6} {upsilon}(4S){yields}BB decays collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we measure B(B{sup 0}{yields}{pi}{sup 0}{pi}{sup 0})=(1.47{+-}0.25{+-}0.12)x10{sup -6}, B(B{sup {+-}}{yields}{pi}{sup {+-}}{pi}{sup 0})=(5.02{+-}0.46{+-}0.29)x10{sup -6}, and B(B{sup {+-}}{yields}K{sup {+-}}{pi}{sup 0})=(13.6{+-}0.6{+-}0.7)x10{sup -6}. We also measure the CP asymmetries C{sub {pi}{sup 0}}{sub {pi}{sup 0}}=-0.49{+-}0.…
Search for the decayB0→KS0KS0KL0
We present the first search for the decay B0 --> K0_S K0_S K0_L using a data sample of 232 million B Bbar pairs. We find no statistically significant evidence for the non-resonant component of this decay. Our central value for the branching fraction, assuming the true Dalitz distribution is uniform and excluding the phi resonance, is B(B0 --> K0_S K0_S K0_L) = (2.4 +2.7 -2.5 +/- 0.6) x 10^{-6} where the errors are statistical and systematic, respectively. We set a single-sided Bayesian upper limit of B(B0 --> K0_S K0_S K0_L) K0_S K0_S K0_L) < 14 x 10^{-6}.
Evidence forB0→ρ0ρ0Decays and Implications for the Cabibbo-Kobayashi-Maskawa Angleα
We search for the decays B(0) --> rho(0)rho(0), B(0) --> rho(0)f(0)(980), and B(0) --> f(0)(980)f(0)(980) in a sample of about 384 x 10(6) Upsilon(4S) --> BB[over] decays collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at Stanford Linear Accelerator Center. We find evidence for B(0) --> rho(0)rho(0) with 3.5 sigma significance and measure the branching fraction B = (1.07 +/- 0.33 +/- 0.19) x 10(-6) and longitudinal polarization fraction f(L) = 0.87 +/- 0.13 +/- 0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the Cabibbo-Kobayashi-Maskawa quark-mixing matrix unitarity angle alpha due to penguin contributio…
A direct measurement of |Vcs| in hadronic W decays using a charm tag
Abstract The inclusive charm production rate in W decays is measured from a study of the properties of final state particles. The sample of W pairs is selected from 67.7 pb−1 collected by ALEPH in 1996 and 1997 at centre-of-mass energies near 172 and 183 GeV in the channels W+W−→4q and W + W − →lνq q . The branching fraction of hadronic W decays to a final state containing a c quark, RWc= Γ(W→cX)/Γ(W→hadrons), is measured to be 0.51±0.05stat±0.03syst. This allows a direct determination of the CKM matrix element |Vcs|=1.00±0.11stat±0.07syst.
Amplitude Analysis of theB±→φK*(892)±Decay
We perform an amplitude analysis of B-+/-->phi(1020)K-*(892)(+/-) decay with a sample of about 384x10(6) B (B) over bar pairs recorded with the BABAR detector. Overall, twelve parameters are measured, including the fractions of longitudinal f(L) and parity-odd transverse f(perpendicular to) amplitudes, branching fraction, strong phases, and six parameters sensitive to CP violation. We use the dependence on the K pi invariant mass of the interference between the J(P)=1(-) and 0(+) K pi components to resolve the discrete ambiguity in the determination of the strong and weak phases. Our measurements of f(L)=0.49 +/- 0.05 +/- 0.03, f(perpendicular to)=0.21 +/- 0.05 +/- 0.02, and the strong phas…
Search for the Standard Model Higgs boson in e+e− collisions at =161, 170 172
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.
Determination of the form factors for the decayB0→D*−l+νland of the CKM matrix element|Vcb|
We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cb vertical bar and of the parameters rho(2), R-1(1), and R-2(1), which fully characterize the form factors for the B-0 -> D*(-)center dot(+)nu(center dot) decay in the framework of heavy-quark effective field theory. The results, based on a selected sample of about 52 800 B-0 -> D*(-)center dot(+)nu(center dot) decays, recorded by the BABAR detector, are rho(2)=1.157 +/- 0.094 +/- 0.027, R-1(1)=1.327 +/- 0.131 +/- 0.043, R-2(1)=0.859 +/- 0.077 +/- 0.021, and F(1)vertical bar V-cb vertical bar=(34.7 +/- 0.4 +/- 1.0)x10(-3). The first error is the statistical and the second is the systematic unce…
Study ofB0→ρ+ρ−decays and constraints on the CKM angleα
We present results from an analysis of B0→ρ+ρ- decays using (383.6±4.2)×106 BB pairs collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The measurements of the B0→ρ+ρ- branching fraction, longitudinal polarization fraction fL, and the CP-violating parameters Slong and Clong are as follows: B(B0→ρ+ρ-)=(25.5±2.1(stat)-3.9+3.6(syst))×10-6, fL=0.992±0.024(stat)-0.013+0.026(syst), Slong=-0.17±0.20(stat)-0. 06+0.05(syst), Clong=0.01±0.15(stat)±0.06(syst). We determine the unitarity triangle angle α, using an isospin analysis of B→ρρ decays. One of the two solutions, α=[73.1,117.0]° at 68% confidence level, is compatible with standard model-based fits of existing da…
Search forB+→τ+νdecays with hadronicBtags
We present a search for the decay B{sup +}{yields}{tau}{sup +}{nu} using 383x10{sup 6} BB pairs collected at the {upsilon}(4S) resonance with the BABAR detector at the SLAC PEP-II B Factory. We select a sample of events with one completely reconstructed tag B in a hadronic decay mode (B{sup -}{yields}D{sup (*)0}X{sup -}), and examine the rest of the event to search for a B{sup +}{yields}{tau}{sup +}{nu} decay. We identify the {tau} lepton in the following modes: {tau}{sup +}{yields}e{sup +}{nu}{nu}, {tau}{sup +}{yields}{mu}{sup +}{nu}{nu}, {tau}{sup +}{yields}{pi}{sup +}{nu}, and {tau}{sup +}{yields}{pi}{sup +}{pi}{sup 0}{nu}. We find a 2.2{sigma} excess in data and measure a branching frac…
Search for sleptons in e+e− collisions at centre-of-mass energies of 161 GeV and 172 GeV
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.
Search for Supersymmetric Particles in e+e- Collisions at sqrt(s) up to 202GeV and Mass Limit for the Lightest Neutralino
Searches for pair production of squarks, sleptons, charginos, and neutralinos are performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies from 188.6 to 201.6 GeV. No evidence for any such signals is observed in a total integrated luminosity of about 410pb-1. The negative results of the searches are translated into exclusion domains in the space of the relevant MSSM parameters, which improve significantly on the constraints set previously. Under the assumptions of gaugino and sfermion mass unification, these results allow a 95% C.L. lower limit of 37GeV/c2 to be set on the mass of the lightest neutralino for any tan beta and sfermion mass. Additional constra…
Measurement of W-pair production in e+e- collisions at 183 GeV
The production of W+W- pairs is analysed in a data sample collected by ALEPH at a mean centre-of-mass energy of 182.7 GeV, corresponding to an integrated luminosity of 57 pb-1. Cross sections are given for different topologies of W decays into leptons or hadrons. Under Standard Model assumptions for the W-pair production and decay, the W-pair cross section is measured to be 15.57+-0.62(stat.)+-0.29(syst.) pb. Using also the W-pair data samples collected by ALEPH at lower centre-of-mass energies, the decay branching ratio of the W boson into hadrons is measured to be B(W->hadrons)= 68.93+-1.21(stat.)+-0.51(syst.)%, allowing a determination of the CKM matrix element |Vcs|= 1.043 +- 0.058(s…
Inclusive π±, K± and(p,p¯) differential cross-sections at the Z resonance
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.
Measurement of theB−→D0K*−branching fraction
From a sample of 232 million {Upsilon}(4S) {yields} B{bar B} events collected with the BABAR detector at the PEP-II B Factory in 1999-2004, they measure the B{sup -} {yields} D{sup 0} K*{sup -}(892) decay branching fraction using events where the K*{sup -} is reconstructed in the K{sub S}{sup 0}{pi}{sup -} mode and the D{sup 0} in the K{sup -}{pi}{sup +}, K{sup -}{pi}{sup +}{pi}{sup 0}, and K{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -} channels: {Beta}(B{sup -} {yields} D{sup 0}K*{sup -}(892)) = (5.29 {+-} 0.30 (stat) {+-} 0.34 (syst)) x 10{sup -4}.
Improved measurements of the branching fractions forB0→π+π−andB0→K+π−, and a search forB0→K+K−
We present measurements of the branching fractions for the charmless two-body decays B0→π+π- and B0→K+π-, and a search for the decay B0→K+K-. We include the effects of final-state radiation from the daughter mesons for the first time, and quote branching fractions for the inclusive processes B0→h+h′-nγ, where h and h′ are pions or kaons. The maximum value of the sum of the energies of the n undetected photons, Eγmax, is mode-dependent. Using a data sample of approximately 227×106 Υ(4S)→BB decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we measure: B(B0→π+π-nγ;Eγmax =150MeV)=(5.1±0.4±0.2) ×10-6, B(B0→K+π-nγ;Eγmax =105MeV)=(18.1±0. 6±0.6)×10-6, …
Observation of a Charmed Baryon Decaying toD0pat a Mass Near2.94 GeV/c2
A search for charmed baryons decaying to $D^0 p$ reveals two states: the $\Lambda_c(2880)^+$ baryon and a previously unobserved state at a mass of [$2939.8\pm 1.3 \text{(stat.)}\pm 1.0 \text{(syst.)}$]~\mevcc and with an intrinsic width of [$17.5\pm 5.2 \text{(stat.)}\pm 5.9 \text{(syst.)}$]~\mev. Consistent and significant signals are observed for the $K^-\pi^+$ and $K^-\pi^+\pi^-\pi^+$ decay modes of the $D^0$ in 287 ${\rm fb}^{-1}$ annihilation data recorded by the BaBar detector at a center-of-mass energy of 10.58~${\rm GeV}/c^2$. There is no evidence in the $D^+ p$ spectrum of doubly-charged partners. The mass and intrinsic width of the $\Lambda_c(2880)^+$ baryon and relative yield of …
Observation of Tree-LevelBDecays withss¯Production from Gluon Radiation
We report on our search for decays proceeding via a tree-level b-->c quark transition in which a gluon radiates into an ss[over ] pair. We present observations of the decays B;{-}-->D_{s};{+}K;{-}pi;{-} and B[over ];{0}-->D_{s};{+}K_{S};{0}pi;{-} and evidence for B;{-}-->D_{s};{+}K;{-}K;{-} and set upper limits on the branching fractions for B[over ];{0}-->D_{s};{+}K_{S};{0}pi;{-} and B;{-}-->D_{s};{+}K;{-}K;{-} using 383x10;{6} Upsilon(4S)-->BB[over ] events collected by the BABAR detector at SLAC. We present evidence that the invariant mass distributions of D_{s};{+}K;{-} pairs from B;{-}-->D_{s};{+}K;{-}pi;{-} decays are inconsistent with the phase-space model, suggesting the presence of…
Observation of the Decay B+→K+K−π+
We report the observation of charmless hadronic decays of charged B mesons to the final state K + K − π + . Using a data sample of 347.5 fb − 1 collected at the Υ ( 4 S ) resonance with the BABAR detector, we observe 429 ± 43 signal events with a significance of 9.6 σ . We measure the inclusive branching fraction B ( B + → K + K − π + ) = [ 5.0 ± 0.5 ( stat ) ± 0.5 ( syst ) ] × 10 − 6 . Inspection of the Dalitz plot of signal candidates shows a broad structure peaking near 1.5 GeV / c 2 in the K + K − invariant mass distribution. We find the direct C P asymmetry to be consistent with zero.
Thee+e−→2(π+π−)π0,2(π+π−)η,K+K−π+π−π0andK+K−π+π−ηcross sections measured with initial-state radiation
We study the processes $e^+ e^-\to 2(\pi^+\pi^-)\pi^0\gamma$, $2(\pi^+\pi^-)\eta\gamma$, $K^+ K^-\pi^+\pi^-\pi^0\gamma$ and $K^+ K^-\pi^+\pi^-\eta\gamma$ with the hard photon radiated from the initial state. About 20000, 4300, 5500 and 375 fully reconstructed events, respectively, are selected from 232 fb$^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective $e^+ e^-$ center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct \epem measurements, currently available only for the $\eta\pi^+\pi^-$ and $\omega\pi^+\pi^-$ submodes of the $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$ channel. Studyi…
Precision measurement of the Λ+c baryon mass
The $\Lambda_c^+$ baryon mass is measured using $\Lambda_c^+\to\Lambda K^0_S K^+$ and $\Lambda_c^+\to\Sigma^0 K^0_S K^+$ decays reconstructed in 232 fb$^{-1}$ of data collected with the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ storage ring. The $\Lambda_c^+$ mass is measured to be $2286.46\pm0.14\mathrm{MeV}/c^2$. The dominant systematic uncertainties arise from the amount of material in the tracking volume and from the magnetic field strength.
Search for doubly charmed baryonsΞcc+andΞcc++inBABAR
We search for the production of doubly charmed baryons in e(+)e(-) annihilations at or near a center-of-mass energy of 10.58 GeV, in a data sample with an integrated luminosity of 232 fb(-1) recorded with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. We search for Xi(+)(cc) baryons in the final states Lambda K-+(c)-pi(+) and Xi(0)(c)pi(+), and Xi(++)(cc) baryons in the final states Lambda K-+(c)-pi(+)pi(+) and Xi(0)(c)pi(+)pi(+). We find no evidence for the production of doubly charmed baryons.
Branching fraction andCP-violation charge asymmetry measurements forB-meson decays toηK±,ηπ±,η′K,η′π±,ωK, andωπ±
The authors present measurements of the branching fractions for B{sup 0} meson decays to {eta}{prime}K{sup 0} and {omega}K{sup 0}, and of the branching fractions and CP-violation charge asymmetries for B{sup +} meson decays to {eta}{pi}{sup +}, {eta}K{sup +}, {eta}{prime}{pi}{sup +}, {eta}{prime}K{sup +}, {omega}{pi}{sup +}, and {omega}K{sup +}. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 383 million B{bar B} pairs produced in e{sup +}e{sup -} annihilation. The measurements agree with previous results; they find no evidence for direct CP violation.
Search for the decay of aB0orB¯0meson toK¯*0K0orK*0K¯0
We present a search for the decay of a B0 or B0bar meson to a K*0bar K0 or K*0 K0bar final state, using a sample of approximately 232 million BBbar events collected with the BABAR detector at the PEP-II asymmetric energy e+e- collider at SLAC. The measured branching fraction is B(B0 --> K*0bar K0) + B(B0 --> K*0 K0bar) = (0.2+0.9-0.8+0.1-0.3)x 10-6. We obtain the following upper limit for the branching fraction at 90% confidence level: B(B0 --> K*0bar K0) + B(B0 --> K*0 K0bar) phi K0 from sin(2beta).
Measurement of thett¯production cross section inpp¯collisions ats=1.96 TeVusing soft electronb-tagging
The authors present a measurement of the t{bar t} production cross section using events with one charged lepton and jets from p{bar p} collisions at a center-of-mass energy of 1.96 TeV. A b-tagging algorithm based on the probability of displaced tracks coming from the event interaction vertex is applied to identify b quarks from top decay. Using 318 pb{sup -1} of data collected with the CDF II detector, they measure the t{bar t} production cross section in events with at least one restrictive (tight) b-tagged jet and obtain 8.9{sub -1.0}{sup +1.0}(stat.){sub -1.0}{sup +1.1}(syst.) pb. The cross section value assumes a top quark mass of m{sub t} is presented in the paper. This result is cons…
Measurement of theτ−→K−π0ντbranching fraction
A measurement of the tau(-)-> K-pi(0)nu(tau) branching fraction has been made using 230.2 fb(-1) of data recorded by the BABAR detector at the PEP-II e(+)e(-) collider, located at the Stanford Linear Accelerator Center (SLAC), at a center-of-mass energy root s close to 10.58 GeV. We measure B(tau(-)-> K-pi(0)nu(tau))=(0.416 +/- 0.003(stat)+/- 0.018(syst))%.
Searches for scalar top and scalar bottom quarks at LEP2
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 --> c chi, stop --> b l snu, and sbottom --> b chi. For the channel stop --> 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…
Measurement ofB¯0→D(*)0K¯(*)0branching fractions
We present a study of the decays (B) over bar (0)-> D-(*)0(K) over bar ((*)0) using a sample of 226x10(6) Upsilon(4S)-> B (B) over bar decays collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at SLAC. We report evidence for the decay of B-0 and (B) over bar (0) mesons to the (DKS0)-K-*0 final state with an average branching fraction B(B-0 ->(DK0)-K-*0)equivalent to(B((B) over bar (0)-> D-*0(K) over bar (0))+B(B-0 ->(DK0)-K-*0))/2=(3.6 +/- 1.2 +/- 0.3)x10(-5). Similarly, we measure B(B-0 ->(DK0)-K-0)equivalent to(B((B) over bar (0)-> D-0(K) over bar (0))+B(B-0 ->(DK0)-K-0))/2=(5.3 +/- 0.7 +/- 0.3)x10(-5) for the (DKS0)-K-0 final state. We measure B((K) over …
Measurements ofCP-Violating Asymmetries in the DecayB0→K+K−K0
The authors analyze the decay B{sup 0} {yields} K{sup +}K{sup -}K{sup 0} using 383 million B{bar B} events collected by the BABAR detector at SLAC to extract CP violation parameter values over the Dalitz plot. Combining all K{sup +}K{sup -}K{sup 0} events, they find A{sub CP} = -0.015 {+-} 0.077 {+-} 0.053 and {beta}{sub eff} = 0.352 {+-} 0.076 {+-} 0.026 rad, corresponding to a CP violation significance of 4.8{sigma}. A second solution near {pi}/2 - {beta}{sub eff} is disfavored with a significance of 4.5{sigma}. They also report A{sub CP} and {beta}{sub eff} separately for decays to {phi}(1020)K{sup 0}, f{sub 0}(980)K{sup 0}, and K{sup +}K{sup -}K{sup 0} with m{sub K{sup +}K{sup -}} > 1.1…
Measurement ofCPViolation Parameters with a Dalitz Plot Analysis ofB±→Dπ+π−π0K±
We report the results of a CP violation analysis of the decay B-+/- -> D pi+pi(-)pi K-0(+/-), where D-pi(+)pi(-)pi(0) indicates a neutral D meson detected in the final state pi(+)pi(-)pi(0), excluding K-S(0)pi(0). The analysis makes use of 324x10(6) e(+)e -> B (B) over bar events recorded by the BABAR experiment at the PEP-II e(+)e(-) storage ring. Analyzing the pi(+)pi(-)pi(0) Dalitz plot distribution and the B-+/- -> D-pi(+)pi(-)pi K-0(+/-) branching fraction and decay rate asymmetry, we find the following one-standard-deviation constraints on the amplitude ratio and on the weak and strong phases: 0.06 pi(+)pi(-)pi(0) decay amplitude.
Measurements of branching fractions, polarizations, and directCP-violation asymmetries inB+→ρ0K*+andB+→f0(980)K*+decays
We report searches for B-meson decays to the charmless final states rho K* and f0(980) K* with a sample of 232 million BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We measure the following branching fractions in units of 10^{-6}: B (B+ --> rho0 K*+) = 3.6 +/- 1.7 +/- 0.8 ( rho+ K*0) = 9.6 +/- 1.7 +/- 1.5, B (B0 --> rho- K*+) = 5.4 +/- 3.6 +/- 1.6 ( rho0 K*0) = 5.6 +/- 0.9 +/- 1.3, B (B+ --> f0(980) K*+) = 5.2 +/- 1.2 +/- 0.5, and B (B0 --> f0(980) K*0) = 2.6 +/- 0.6 +/- 0.9 ( rho+ K*0) = 0.52 +/- 0.10 +/- 0.04, f_L (B0 --> rho0 K*0) = 0.57 +/- 0.09 +/- 0.08, A_CP (B+ --> rho+ K*0) = -0.01 +/- 0.16 +/- 0.02, A_CP (B0 --> rho0 K*0) = 0.0…
Measurement of the absolute branching fraction of D-0 -> K-pi(+)
We measure the absolute branching fraction for D0 --> K- pi+ using partial reconstruction of B0bar --> D^{*+} X \ell^{-} \bar{\nu}_{\ell} decays, in which only the charged lepton and the pion from the decay D^{*+} --> D0 pi^+ are used. Based on a data sample of 230 million B Bbar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we obtain the absolute branching fractions of D0 --> K- pi+ = (4.007 \pm 0.037 \pm 0.072)%, where the first uncertainty is statistical and the second is systematic.
Search for the glueball candidates f0(1500) and fJ(1710) in γγ collisions
Abstract Data taken with the ALEPH detector at LEP1 have been used to search for γγ production of the glueball candidates f0(1500) and fJ(1710) via their decay to π+π−. No signal is observed and upper limits to the product of γγ width and π+π− branching ratio of the f0(1500) and the fJ(1710) have been measured to be Γ(γγ→f 0 (1500))· B R (f 0 (1500)→π + π − ) keV and Γ(γγ→f J (1710))· B R (f J (1710)→π + π − ) keV at 95% confidence level.
Branching fraction and charge asymmetry measurements in B→J/ψππ decays
The authors study the decays B{sup 0} {yields} J/{psi} {pi}{sup +}{pi}{sup -} and B{sup +} {yields} J/{psi} {pi}{sup +}{pi}{sup 0}, including intermediate resonances, using a sample of 382 million B{bar B} pairs recorded by the BABAR detector at the PEP-II e{sup +}e{sup -} B factory. They measure the branching fractions {Beta}(B{sup 0} {yields} J/{psi} {rho}{sup 0}) = (2.7 {+-} 0.3 {+-} 0.17) x 10{sup -5} and {Beta}(B{sup +} {yields} J/{psi} {rho}{sup +}) = (5.0 {+-} 0.7 {+-} 0.31) x 10{sup -5}. The authors also set the following upper limits at the 90% confidence level: {Beta}(B{sup 0} {yields} J/{psi} {pi}{sup +}{pi}{sup -} non-resonant) < 1.2 x 10{sup -5}, {Beta}(B{sup 0} {yields} J/{psi…
Observation ofB+→ρ+K0and measurement of its branching fraction and charge asymmetry
We present the first observation of the decay B+→ρ+K0, using a data sample of 348fb-1 collected at the Υ(4S) resonance with the BABAR detector. The branching fraction and charge asymmetry are measured to be (8.0-1.3+1.4±0.6)×10-6 and (-12.2±16.6±2.0)%, respectively, where the first uncertainty is statistical and the second is systematic. The charge asymmetry is defined by Ach=(ΓB - ΓB+)/(ΓB-+ΓB+) with ΓB± the B± decay rate. The significance of the observed branching fraction, including systematic uncertainties, is 7.9 standard deviations. © 2007 The American Physical Society.
Search forD0−D¯0Mixing and a Measurement of the Doubly Cabibbo-Suppressed Decay Rate inD0→KπDecays
The authors present a search for D{sup 0}-{bar D}{sup 0} mixing using regions of phase space in which the rate of doubly Cabibbo-suppressed decays D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} relative to Cabibbo-favored decays D{sup 0} {yields} K{sup -} {pi}{sup +}{pi}{sup 0} is reduced. They analyze 230.4 fb{sup -1} of data collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at SLAC. They present results with and without the assumption of CP conservation. Assuming CP conservation, they measure the time-integrated mixing rate R{sub M} = (0.023{sub -0.014}{sup +0.018}(stat.) {+-} 0.004(syst.))%, and R{sub M} < 0.054% at the 95% confidence level. They find that the d…
Observation of charmless hadronic B decays
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)(…
Search for the rare decaysB0→Ds(*)+a0(2)−
We have searched for the decays B{sup 0}{yields}D{sub s}{sup +}a{sub 0}{sup -}, B{sup 0}{yields}D{sub s}*{sup +}a{sub 0}{sup -}, B{sup 0}{yields}D{sub s}{sup +}a{sub 2}{sup -} and B{sup 0}{yields}D{sub s}*{sup +}a{sub 2}{sup -} in a sample of about 230x10{sup 6} {upsilon}(4S){yields}BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We find no evidence for these decays and set upper limits at 90% C.L. on the branching fractions: B(B{sup 0}{yields}D{sub s}{sup +}a{sub 0}{sup -})<1.9x10{sup -5}, B(B{sup 0}{yields}D{sub s}*{sup +}a{sub 0}{sup -})<3.6x10{sup -5}, B(B{sup 0}{yields}D{sub s}{sup +}a{sub 2}{sup -})<1.9x10{sup -4}, and B(B{sup 0}{yields}D…
Measurements of the branching fraction and time-dependentCPasymmetries ofB0→J/ψπ0decays
We present measurements of the branching fraction and time-dependent CP asymmetries in B{sup 0} {yields} J/{psi}{pi}{sup 0} decays based on (231.8 {+-} 2.6) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We obtain a branching fraction {Beta}(B{sup 0} {yields} J/{psi}{pi}{sup 0}) = (1.94 {+-} 0.22 (stat) {+-} 0.17 (syst)) x 10{sup -5}. We also measure the CP asymmetry parameters C = -0.21 {+-} 0.26 (stat) {+-} 0.06 (syst) and S = -0.68 {+-} 0.30 (stat) {+-} 0.04 (syst).
Observation of a NewDsMeson Decaying toDKat a Mass of2.86 GeV/c2
We observe a new D_s meson with mass (2856.6 +/- 1.5_{stat.} +/- 5.0_{syst.}) MeV/c^2 and width (48 +/- 7_{stat.} +/- 10_{syst.}) MeV decaying into D^0 K^+ and D^+K^0_S. In the same mass distributions we also observe a broad structure with mass (2688 +/- 4_{stat.} +/- 3_{syst.}) MeV/c^2 and width (112 +/- 7_{stat.} +/- 36_{syst.}) MeV. To obtain this result we use 240 fb^-1 of data recorded by the BaBar detector at the PEP-II asymmetric-energy e^+e^- storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.
Measurement of the D∗± cross section in two photon collisions at LEP
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…
Evidence for ChargedBMeson Decays toa1±(1260)π0anda10(1260)π±
We present measurements of the branching fractions for the decays B±→a1±(1260)π0 and B±→a10(1260)π± from a data sample of 232×106 BB pairs produced in e+e- annihilation through the Υ(4S) resonance. We measure the branching fraction B(B±→a1±(1260)π0)×B(a1±(1260) →π-π+π±)=(13.2±2.7±2.1)×10-6 with a significance of 4.2σ, and the branching fraction B(B±→ a10(1260)π±)×B(a10(1260)→π-π+π0)=(20.4±4. 7±3.4)×10-6 with a significance of 3.8σ, where the first error quoted is statistical and the second is systematic. © 2007 The American Physical Society.
Search forB0→ϕ(K+π−)decays with largeK+π−invariant mass
Motivated by the polarization anomaly in the B→ (1020)K*(892) decay, we extend our search for other K* final states in the decay B0→ (1020)K*0 with the K*0→K+π- invariant mass above 1.6 GeV. The final states considered include the K*(1680)0, K3*(1780)0, K4*(2045)0, and a Kπ spin-zero nonresonant component. We also search for B0→ D0 decay with the same final state. The analysis is based on a sample of about 384×106 BB pairs recorded with the BABAR detector. We place upper limits on the branching fractions B(B0→ K*(1680)0)<3.5×10-6, B(B0→ K3*(1780)0) <2.7×10-6, B(B0→ K4*(2045)0)<15.3×10-6, and B(B0→ D0)<11.7×10-6 at 90% C.L. The nonresonant contribution is consistent with the measurements in …
Searches for sleptons and squarks in e(+)e(-) collisions at 189 GeV
The data collected at a centre-of-mass energy of 188.6 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 173.6 pb$^{-1}$, are analysed in a search for the scalar partners of quarks and leptons predicted in supersymmetric models. No evidence for any such particles was found in the decay channels $\sle \to \ell \chi$, $\stop \rightarrow \mathrm{c}\neu$, $\stop \rightarrow \mathrm{b}\ell\snu$, $\sbot \rightarrow \mathrm{b}\neu$, and $\mathrm{\tilde{q}} \rightarrow \mathrm{q}\neu$. Improved mass lower limits have been obtained in the framework of the Minimal Supersymmetric Standard Model.
Measurements of |Vcb|, form factors and branching fractions in the decays → ℓ and → ℓ
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…
Thee+e−→3(π+π−),2(π+π−π0)andK+K−2(π+π−)cross sections at center-of-mass energies from production threshold to 4.5 GeV measured with initial-state radiation
We study the processes e^+e^- → 3(π^+π^-)γ, 2(π^+π^-π^0)γ and K^+K^-2(π^+π^-)γ, with the photon radiated from the initial state. About 20 000, 33 000 and 4000 fully reconstructed events, respectively, have been selected from 232 fb^(-1) of BABAR data. The invariant mass of the hadronic final state defines the effective e^+e^- center-of-mass energy, so that these data can be compared with the corresponding direct e^+e^- measurements. From the 3(π^+π^-), 2(π^+π^-π^0) and K^+K^-2(π^+π^-) mass spectra, the cross sections for the processes e^+e^- → 3(π^+π^-), e^+e^- → 2(π^+π^-π^0) and e^+e^- → K^+K^-2(π^+π^-) are measured for center-of-mass energies from production threshold to 4.5 GeV. The unc…
The BaBar detector: Upgrades, operation and performance
The BABAR detector operated successfully at the PEP-Il asymmetric e(+) e(-) collider at the SLAC National Accelerator Laboratory from 1999 to 2008. This report covers upgrades, operation, and performance of the collider and the detector systems, as well as the trigger, online and offline computing, and aspects of event reconstruction since the beginning of data taking.
Search for the standard model Higgs boson at the LEP2 collider near
Abstract During 1997 the ALEPH experiment at LEP gathered 57 pb −1 of data at centre-of-mass energies near 183 GeV . These data are used to look for possible signals from the production of the Standard Model Higgs boson in the reaction e+e−→HZ. No evidence of a signal is found in the data; seven events are selected, in agreement with the expectation of 7.2 events from background processes. This observation results in an improved lower limit on the mass of the Higgs boson: m H >87.9 GeV /c 2 at 95% confidence level.
Search for the decay B0→a1±ρ∓
We present a search for the rare B-meson decay B-0 -> a(1)(+/-)rho(-/+) with a(1)(+/-)->pi(+)pi(-)pi(+/-). We use (110 +/- 1.2)x10(6) Upsilon(4S)-> B (B) over bar decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We obtain an upper limit of 30x10(-6) (90%C.L.) for the branching fraction product B(B-0 -> a(1)(+/-)rho(-/+))B(a(1)(+/-)->pi(+)pi(-)pi(+/-)), where we assume that the a(1)(+/-) decays exclusively to rho(0)pi(+/-).
Measurement of theB±→ρ±π0branching fraction and directCPasymmetry
We present improved measurements of the branching fraction and CP asymmetry for the process B±→ρ±π0. The data sample corresponding to 211fb-1 comprises 232×106 Υ(4S)→BB decays collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. The yield and CP asymmetry are measured using an extended maximum likelihood fitting method. The branching fraction and CP asymmetry are found to be B(B±→ρ±π0)=[10.2±1.4(stat)±0.9(syst)] ×10-6 and ACP(B±→ρ±π0)=-0.01±0.13(stat) ±0.02(syst). © 2007 The American Physical Society.
Structure at 2175 MeV ine+e−→ϕf0(980)observed via initial-state radiation
We study the initial-state-radiation processes e+e-→K+K-π+π- γ and e+e-→K+K-π0π0γ using an integrated luminosity of 232fb-1 collected at the Υ(4S) mass with the BABAR detector at SLAC. Even though these reactions are dominated by intermediate states with excited kaons, we are able to study for the first time the cross section for e+e-→ (1020)f0(980) as a function of center-of-mass energy. We observe a structure near threshold consistent with a 1 - resonance with mass m=2.175±0. 010±0.015GeV/c2 and width Γ=58±16±20MeV. We observe no Y(4260) signal and set a limit of BY→ π+π-•ΓeeY<0. 4eV (90% confidence level), which excludes some models. © 2006 The American Physical Society.
Search forCPViolation in the DecaysD0→K−K+andD0→π−π+
We report a search for CP violation in the decay modes D±→KS0K±, Ds±→KS0K±, and Ds±→KS0π± using a data set corresponding to an integrated luminosity of 469 fb-1 collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings. The decay rate CP asymmetries, ACP, are determined to be (+0.13±0.36(stat)±0.25(syst))%, (-0.05±0.23(stat)±0.24(syst))%, and (+0.6±2.0(stat)±0.3(syst))%, respectively. These measurements are consistent with zero, and also with the Standard Model prediction [(-0.332±0.006)% for the D±→KS0K± and Ds±→KS0K± modes, and (+0.332±0.006)% for the Ds±→KS0π± mode]. They are the most precise determinations to date.
A study of the decay width difference in the B0s– system using φφ correlations
In a data sample of about four million hadronic Z decays recorded with the ALEPH detector from 1991 to 1995, the decay is observed, based on tagging the final state with two φ mesons in the same hemisphere. The final state is mostly CP even and corresponds to the short-lived B0s mass eigenstate. The branching ratio of this decay is measured to be . A measurement of the lifetime of the B0s(short) gives 1.27±0.33±0.08 ps. The lifetime and branching ratio measurements provide two essentially independent methods of estimating the relative decay width difference ΔΓ/Γ in the B0s– system, corresponding to an average value ΔΓ/Γ=(25+21−14)%.
Measurement of decay amplitudes ofB→J/ψK*,ψ(2S)K*, andχc1K*with an angular analysis
We perform the first three-dimensional measurement of the amplitudes of B→ψ(2S)K* and B→χc1K* decays and update our previous measurement for B→J/ψK*. We use a data sample collected with the BABAR detector at the PEP-II storage ring, corresponding to 232×106 BB pairs. The longitudinal polarization of decays involving a JPC=1++ χc1 meson is found to be larger than that with a 1 - J/ψ or ψ(2S) meson. No direct CP-violating charge asymmetry is observed. © 2007 The American Physical Society.
Search for prompt production ofχcandX(3872)ine+e−annihilations
We have searched for prompt production of χc1, χc2 and X(3872) in continuum e+e- annihilations using a 386fb-1 data sample collected around s=10.6GeV with the BABAR detector using the γJ/ψ decay mode. After accounting for the feed-down from ψ(2S)→γχc1,2, no significant signal for prompt χc1,2 production is observed. We present improved upper limits at 90% confidence level on the production cross sections of 77fb for χc1 and 79fb for χc2, for events where the χc momentum exceeds 2.0 GeV and there are at least three additional charged tracks. These limits are consistent with NRQCD predictions. We also set an upper limit on the prompt production of X(3872) through the decay X(3872)→γJ/ψ. © 200…
Search for the DecayB+→K+τ∓μ±
We present a search for the lepton flavor violating decay B+-->K+ tau-/+ mu+/- using 383 x 10;{6} BB[over ] events collected by the BABAR experiment. The branching fraction for this decay can be substantially enhanced in new physics models. The kinematics of the tau from the signal B decay are inferred from the K+, mu, and other B in the event, which is fully reconstructed in one of a variety of hadronic decay modes, allowing the signal B candidate to be fully reconstructed. We observe no excess of events over the expected background and set a limit of B(B+-->K+ tau mu)<7.7 x 10(-5) at 90% confidence level, where the branching fraction is for the sum of the K+ tau- mu+ and K+ tau+mu- final …
Observation ofBMeson Decays tob1πandb1K
We present the results of searches for decays of B mesons to final states with a b_1 meson and a charged pion or kaon. The data, collected with the BaBar detector at the Stanford Linear Accelerator Center, represent 382 million B-Bbar pairs produced in e+e- annihilation. The results for the branching fractions are, in units of 10^{-6}, B(B+ -> b1^0 pi+) = 6.7 +/- 1.7 +/- 1.0 (4.0 sigma), B(B+ -> b1^0 K+ = 9.1+/- 1.7+/- 1.0 (5.3 sigma), B(B0 -> b1^-/+ pi^+/-) = 10.9 +/- 1.2 +/- 0.9 (8.9 sigma), and B(B0 -> b1^-K+) = 7.4 +/- 1.0 +/- 1.0 (6.1 sigma), with the assumption that B(b_1 -> omega pi)=1. We also measure charge and flavor asymmetries Ach(B+ -> b1^0 pi+) = 0.05 +/- 0.16 +/- 0.02, Ach(B+…
Measurements of the Branching Fraction andCP-Violation Asymmetries inB0→f0(980)KS0
The authors present measurements of the branching fraction and CP-violating asymmetries in the decay B{sup 0} {yields} f{sub 0}(980)K{sub S}{sup 0}. The results are obtained from a data sample of 123 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays. From a time-dependent maximum likelihood fit they measure the branching fraction {Beta}(B{sup 0} {yields} f{sub 0}(980)({yields}{Pi}{sup +}{pi}{sup 0})K{sup 0}) = (6.0 {+-} 0.9 {+-} 0.6 {+-} 1.2) x 10{sup -6}, the mixing-induced CP violation parameter S = 1.62{sub -0.51}{sup +0.56} {+-} 0.09 {+-} 0.04 and the direct CP violation parameter C = 0.27 {+-} 0.36 {+-} 0.10 {+-} 0.07, where the first errors are statistical, the second systematic and …
Search for single top production in e+e− collisions at –202 GeV
Abstract Single top production via flavour changing neutral currents in the reactions e + e − → t c / u is searched for in approximately 411 pb −1 of data collected by ALEPH at centre-of-mass energies in the range between 189 and 202 GeV. In total, 58 events are selected in the data to be compared with 50.3 expected from Standard Model backgrounds. No deviation from the Standard Model expectation is observed. Upper limits at 95% CL on single top production cross sections at s =189 –202 GeV are derived. A model-dependent limit on the sum of branching ratios BR(t→Zc)+BR(t→Zu)
Study ofBMeson Decays with Excitedηandη′Mesons
Using 383 million B{bar B} pairs from the BABAR data sample, they report results for branching fractions of six charged B-meson decay modes, where a charged kaon recoils against a charmless resonance decaying to K{bar K}* or {eta}{pi}{pi} final states with mass in the range (1.2-1.8) GeV/c{sup 2}. They observe a significant enhancement at the low K{bar K}* invariant mass which is interpreted as B{sup +} {yields} {eta}(1475)K{sup +}, find evidence for the decay B{sup +} {yields} {eta}(1295)K{sup +}, and place upper limits on the decays B{sup +} {yields} {eta}(1405)K{sup +}, B{sup +} {yields} f{sub 1}(1285)K{sup +}, B{sup +} {yields} f{sub 1}(1420)K{sup +}, and B{sup +} {yields} {phi}(1680)K{…
Measurements ofΛc+branching fractions of Cabibbo-suppressed decay modes involvingΛandΣ0
We measure the branching ratios of the Cabibbo-suppressed decays $\Lambda^+_c$ $\to$ $\Lambda$ $K^+$ and $\Lambda^+_c$ $\to$ $\Sigma^{0}$ $K^+$ %(measured with improved accuracy). relative to the Cabibbo-favored decay modes $\Lambda^+_c$ $\to$ $\Lambda$ $\pi^+$ and $\Lambda^+_c$ $\to$ $\Sigma^{0}$ $\pi^+$ to be $ 0.044 \pm 0.004 ~(\textnormal{stat.})~ \pm ~0.003 \~(\textnormal{syst.})$ and $ 0.039~ \pm ~0.005 ~(\textnormal{stat.})~ \pm \~0.003 ~(\textnormal{syst.})$, respectively. We set an upper limit on the branching ratio at 90 % confidence level for $\Lambda^+_c$ $\to$ $\Lambda$ $K^+ \pi^+ \pi^-$ to be $ 4.1 \times ~10^{-2}$ relative to $\Lambda^+_c$ $\to$ $\Lambda$ $\pi^+$ and for $\La…
A measurement of the gluon splitting rate into bb̄ pairs in hadronic Z decays
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 .
Search forD0−D¯0mixing using doubly flavor tagged semileptonic decay modes
We have searched for D0-D0 mixing in D*+→π+D0 decays with D0→K(*)eν in a sample of e+e-→cc events produced near 10.58 GeV. The charge of the slow pion from charged D* decay tags the charm flavor at production, and it is required to be consistent with the flavor of a fully reconstructed second charm decay in the same event. We observe 3 mixed candidates compared to 2.85 background events expected from simulation. We ascribe a 50% systematic uncertainty to this expected background rate. We find a central value for the mixing rate of 0.4×10-4. Using a frequentist method, we set corresponding 68% and 90% confidence intervals at (-5.6,7.4)×10-4 and (-13,12)×10-4, respectively. © 2007 The America…
Bose-Einstein correlations in W-pair decays
Bose-Einstein correlations are studied in semileptonic (WW --> q (q) over bar lv) and fully hadronic (WW --> q (q) over bar q (q) over bar) W-pair decays with the ALEPH detector at LEP at centre-of-mass energies of 172, 183 and 189 GeV. They are compared with those made at the Z peak after correction for the different flavour compositions. A Monte Carlo model of Bose-Einstein correlations based on the JETSET hadronization scheme was tuned to the Z data and reproduces the correlations in the WW --> q (q) over bar lv events. The same Monte Carlo reproduces the correlations in the WW --> q (q) over bar q (q) over bar channel assuming independent fragmentation of the two W's. A variant of this …
Search forB+→X(3872)K+,X(3872)→J/ψγ
In a study of B+ --> J/psi gamma K+ decays, we find evidence for the radiative decay X(3872) --> J/psi gamma with a statistical significance of 3.4 sigma. We measure the product of branching fractions BF(B+ --> X(3872) K+).BF(X(3872) --> J/psi gamma) = (3.3 +/- 1.0 +/- 0.3) x 10^-6, where the uncertainties are statistical and systematic, respectively. We also measure the branching fraction BF(B+ --> chi_c1 K+) = (4.9 +/- 0.2 +/- 0.4) x 10^-4. These results are obtained from (287+/-3) million BBar decays collected at the Y(4S) resonance with the BaBar detector at the PEP-II B Factory at SLAC.
Evidence for the Rare DecayB+→Ds+π0
We have searched for the rare decay B+ -> D-s(+) pi(0). The analysis is based on a sample of 232 X 10(6) Y(4S) -> B (B) over bar decays collected with the BABAR detector at the SLAC PEP-II e(+)e(-) storage ring. We find 19.6 signal events, corresponding to a significance of 4.7 sigma. The extracted signal yield including statistical and systematic uncertainties is 20.1(-6.0-1.5)(+6.8+0.4) and we measure B(B+ -> D-s(+) pi(0)) = (1.5(-0.4)(+0.5) +/- 0.1 +/- 0.2) X x 10(-5), where the first uncertainty is statistical, the second is systematic, and the last is due to the uncertainty on the D-s(+) decay and its daughter decay branching fractions.
Measurements of Branching Fraction, Polarization, and Charge Asymmetry ofB±→ρ±ρ0and a Search forB±→ρ±f0(980)
We measure the branching fraction (B), polarization (f(L)), and CP asymmetry (A(CP)) of B-+/-->rho(+/-)rho(0) decays and search for the decay B-+/-->rho(+/-)f(0)(980) based on a data sample of 231.8x10(6) Upsilon(4S)-> B (B) over bar decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. In B-+/-->rho(+/-)rho(0) decays we measure B=(16.8 +/- 2.2 +/- 2.3)x10(-6), f(L)=0.905 +/- 0.042(-0.027)(+0.023), and A(CP)=-0.12 +/- 0.13 +/- 0.10, and find an upper limit on the branching fraction of B-+/-->rho(+/-)f(0)(980)(->pi(+)pi(-)) decays of 1.9x10(-6) at 90% confidence level.
Search for neutralB-meson decays toa0π,a0K,ηρ0, andηf0
We present a search for B0 decays to charmless final states involving an eta meson, a charged pion and a second charged pion or kaon. The data sample corresponds to 383x10^6 BBbar pairs collected with the BABAR detector operating at the PEP-II asymmetric-energy B Factory at SLAC. We find no significant signals and determine the following 90% C.L. upper limits: BR(B->a0-pi+) x BR(a0- -> etapi-) a0-K+) x BR(a0- -> etapi-) a0(1450)-pi+) x BR(a0(1450)- -> etapi-) a0(1450)-K+) x BR(a0(1450)- -> etapi-) etarho0) eta f0(980)) x BR(f0(980)- -> pi+pi-) < 0.4x10^-6.
Observation ofB+→K¯0K+andB0→K0K¯0
The authors report observations of the b {yields} d penguin-dominated decays B{sup +} {yields} {bar K}{sup 0}K{sup +} and B{sup 0} {yields} K{sup 0}{bar K}{sup 0} in approximately 350 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector. They measure the branching fractions {Beta}(B{sup +} {yields} {bar K}{sup 0}K{sup +}) = (1.61 {+-} 0.44 {+-} 0.09) x 10{sup -6} and {Beta}(B{sup 0} {yields} K{sup 0}{bar K}{sup 0}) = (1.08 {+-} 0.28 {+-} 0.11) x 10{sup -6}, and the CP-violating charge asymmetry {Alpha}{sub CP} ({bar K}{sup 0} K{sup +}) = 0.10 {+-} 0.26 {+-} 0.03. Using a vertexing technique previously employed in several analyses of all-neutral final states conta…
Inclusive semileptonic branching ratios of b hadrons produced in Z decays
A measurement of the inclusive semileptonic branching ratios of b hadrons produced in Z decay is presented, using four million hadronic events collected by the ALEPH detector from 1991 to 1995. Electrons and muons are selected opposite to b-tagged hemispheres. Two different methods are explored to distinguish the contributions from direct $\bl$ and cascade $\bcl$ decays to the total lepton yield. One is based on the lepton transverse momentum spectrum, the other makes use of the correlation between the charge of the lepton and charge estimators built from tracks in the opposite hemisphere of the event. The latter method reduces the dependence on the modelling of semileptonic b decays. The r…
Search for decays ofB0mesons intoe+e−,μ+μ−ande±μ∓final states
We present a search for the decays B0→e+e-, B0→μ+μ-, and B0→e±μ using data collected with the BABAR detector at the PEP-II e+e- collider at SLAC. Using a data set corresponding to 384×106 BB pairs, we do not find evidence of any of the three decay modes. We obtain upper limit on the branching fractions, at 90% confidence level, of B(B0→e+e-)<11.3×10-8, B(B0→μ+μ-)<5.2×10-8, and B(B0→e±μ)<9.2×10-8. © 2008 The American Physical Society.
Measurement of theCP-violating asymmetries inB0→Ks0π0and of the branching fractionB0→K0π0
We present a measurement of the time-dependent CP-violating asymmetries in B-0 -> K-S(0)pi(0) decays based on 383x10(6) Upsilon(4S)-> B (B) over bar events collected by the BABAR experiment at the PEP-II asymmetric-energy B Factory at the Stanford Linear Accelerator Center. We measure the direct CP-violating asymmetry C-KS(0)pi(0)=0.24 +/- 0.15 +/- 0.03 and the CP-violating asymmetry in the interference between mixing and decay S-KS(0)pi(0)=0.40 +/- 0.23 +/- 0.03, where the first errors are statistical and the second are systematic. On the same sample, we measure the decay branching fraction, obtaining B(B-0 -> K-0 pi(0))=(10.3 +/- 0.7 +/- 0.6)x10(-6).
Observation ofB→η′K*and Evidence forB+→η′ρ+
We present an observation of B-->eta'K*. The data sample corresponds to 232x10(6) BB[over ] pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. We measure the branching fractions (in units of 10(-6)) B(B(0)-->eta'K*0)=3.8+/-1.1+/-0.5 and B(B+-->eta'K*+)=4.9(1.7)(+1.9)+/-0.8, where the first error is statistical and the second systematic. A simultaneous fit results in the observation of B-->eta'K* with B(B-->eta'K*)=4.1(-0.9)(+1.0)+/-0.5. We also search for B-->eta'rho and eta'f(0)(980)(f(0)-->pi+pi-) with results and 90% confidence level upper limits B(B+-->eta'rho+)=8.7(-2.8-1.3)(+3.1+2.3) ( eta'rho0) eta'f(0)(980)(f(…
Determination of A(FB)(b) using jet charge measurements in Z decays
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…