Using isolated leptons reconstructed in the Mark II detector to tag bb events, we measure the fraction of bb events in hadronic Z0 decays to be 0.23-0.09+0.11, in good agreement with the standard-model prediction of 0.22. We find (Zbb)=0.43-0.17+0.21 GeV. © 1990 The American Physical Society.

New measurements of Ds+and Ds*+meson production rates from B decays and from qq̄ continuum events near the Y(4S) resonance are presented. Using 20.8 fb-1of data on the Y(4S) resonance and 2.6 fb-1off-resonance, we find the inclusive branching fractions B(B→Ds+X)=(10.93±0.19±0.58±2.73)% and B(B→Ds*+X)=(7.9±0.8±0.7 ±2.0)%, where the first error is statistical, the second is systematic, and the third is due to the Ds+→φπ+branching fraction uncertainty. The production cross sections σ(e+e-→Ds+X) × B(Ds+→φπ+)=7.55±0.20 ±0.34 pb and σ(e+e-→Ds*±X) × B(Ds+→φπ+) = 5.8±0.7±0.5 pb are measured at center-of-mass energies about 40 MeV below the Y(4S) mass. The branching fractions ΣB(B→Ds(*)+D̄(*))=(5.07±0.14±0.30±1.27)% and ∑B(B→Ds*+D̄(*)) =(4.1±0.2±0.4±1.0)% are determined from the Ds(*)+momentum spectra. The mass difference m(Ds+)-m(D+)=98.4±0.1 ±0.3 MeV/c2is also measured.

We report a study of the [Formula presented] meson decays, [Formula presented] , [Formula presented], [Formula presented] , [Formula presented], and [Formula presented] using [Formula presented] [Formula presented] events collected at the [Formula presented] resonance with the BABAR detector at the PEP-II [Formula presented] asymmetric-energy storage ring. We measure the branching fractions [Formula presented] and [Formula presented] , and set upper limits at [Formula presented] confidence level for the branching fractions [Formula presented] , [Formula presented], and [Formula presented] . © 2003 The American Physical Society.

We report a measurement of the CP-violation parameter sin 2β with B0J/ψKS0decays in which the J/ψ decays to hadrons or to muons that do not satisfy our standard identification criteria. With a sample of 88 million BB̄ events collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we reconstruct 100±17 such events, with J/ψ→π-π-π0being the most prevalent, and measure sin2β=1.56± 0.42(stat)±0.21(syst). © 2004 The American Physical Society.

We present a measurement of time-dependent CP-violating asymmetries in neutral B meson decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e-collider at the Stanford Linear Accelerator Center. The data sample consists of 29.7 fb-1recorded at the γ(4S) resonance and 3.9 fb-1off resonance. One of the neutral B mesons, which are produced in pairs at the γ(4S), is fully reconstructed in the CP decay modes J/ ψKS0, ψ(2S)KS0, χc1KS0, J/ψK*0(K*0→KS0π0) and J/ψKL0, or in flavor-eigenstate modes involving D(*)π/p/a1and J/ψK*0(K*0→K+π-). The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. A neural netsvork tagging algorithm is used to recover events without a clear lepton or kaon tag. The proper time elapsed between the decays is determined by measuring the distance between the decay vertices. Wrong-tag probabilities, the time-difference resolution function, and the B0-B̄0oscillation frequency Δmdare measured with a sample of about 6350 fully-reconstructed B0decays in hadronic flavor-eigenstate modes. A maximum-likelihood fit to this flavor eigenstate sample finds Δmd=0.516±0.016(stat)±0.010(syst) ps-1. The value of the asymmetry amplitude sin 2β is determined from a simultaneous maximum-likelihood fit to the time-difference distribution of the flavor-eigenstate sample and about 642 tagged B0decays in the CP-eigenstate modes. We find sin 2β=0.59 ±0.14(stat)±0. 05(syst), demonstrating that CP violation exists in the neutral B meson system. We also determine the value of the CP violation parameter |λ|=0. 93±0.09(stat)±0.03(syst), which is consistent with the expectation of |λ|=1 for no direct CP violation. © 2002 The American Physical Society.

Flavor oscillations of neutral B mesons have been studied in [Formula presented] annihilation data collected with the BABAR detector at center-of-mass energies near the [Formula presented] resonance. The data sample used for this purpose consists of events in which one [Formula presented] meson is reconstructed in a hadronic decay mode, while the flavor of the recoiling [Formula presented] is determined with a tagging algorithm that exploits the correlation between the flavor of the heavy quark and the charges of its decay products. From the time development of the observed mixed and unmixed final states, we determine the [Formula presented] oscillation frequency [Formula presented] to be [Formula presented]. © 2002 The American Physical Society.

BABAR is a solenoidal detector optimized for the asymmetric-energy beams at PEP-II and is described in detail. As such, charged particle (track) momenta are measured with a 5-layer double-sided silicon vertex tracker and a 40-layer drift chamber (DCH) inside a 1.5 T superconducting solenoidal magnet. This paper reports on an observation of the decays B ± →π ± π 0 and B ± →K ± π 0 , a measurement of their CP-violating charge asymmetries, and a search for the decay B 0 →π 0 π 0 , using (87.9±1.0)×10 6 BB̄ pairs collected with the BABAR detector.

The branching fraction Β(Β0→rho;- e+v)=(3.29±0.42±0.47±0.55)x10-4 was measured using isospin constraints and extrapolating to all electron energies according to five different form-factor calculations. The errors are statistical, systematic, and theoretical. The value of |Vub| determined by the same form-factor calculations is |Vub|=(3/64±0.22±0.25-0.56 +0.39) X 10-3.

The BaBar detector operated successfully at the PEP-II 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. © 2013 Elsevier B.V.

The Mark II detector has been upgraded in preparation for its role as the first detector to take data at the Stanford Linear Collider. The new detector components include the central drift chamber, the time-of-flight system, the coil, the endcap electromagnetic calorimeters and the beam energy and luminosity measuring devices. There have also been improvements in detector hermeticity. All of the major components were installed for a test run at the PEP storage ring (√s = 29 GeV) in 1985. This paper describes the upgraded detector, including its trigger and data acquisition systems, and gives performance figures for its components. Future improvements are also discussed. © 1989.