We report measurements of the inclusive electron momentum spectra in decays of charged and neutral B mesons, and of the ratio of semileptonic branching fractions B(B+→Xeν) and B(B0→Xeν). These were performed on a sample of 231×106 BB̄ events recorded with the BABAR detector at the Υ(4S) resonance. Events are selected by fully reconstructing a hadronic decay of one B meson and identifying an electron among the decay products of the recoiling B̄ meson. We obtain B(B+→Xeν)/B(B0→Xeν)=1. 074±0.041(stat)±0.026(syst). © 2006 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.

We report the observation of 823±57 B0 and 970±65 B+ decays to doubly charmed final states D̄ (*)D(*)K, where D̄(*) and D(*) are fully reconstructed and K is either a K ± or a K0. We use a sample of 82.3 ±0.9 million B B̄ events collected between 1999 and 2002 with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. The 22 ossible B decays to D̄(*)D(*)K are reconstructed exclusively and the corresponding branching fractions or limits are determined. The branching fractions of the B0 and of the B + to D̄(*)D(*)K are found to be Β(B0→D̄(*)D(*)K) = [4.3±0.3(stat)±0.6(syst)]%, Β(B+→D̄ (*)D(*)K) = [3.5±0.3(stat)±0. 5(syst)]%.A search for decays to orbitally excited Ds states, B→D̄(*)DsJ+(DsJ+→D(*)0K+), is also performed. No statistically significant-contributions from Ds1+(2536) →D*0K+ and DsJ+(2573) →D0K+ to the D̄(*)D (*)0K+ final state are found and we set 90% C.L. limits on their production rates. © 2003 The American Physical Society.

We present branching fraction measurements of charged and neutral B decays to Dπ-, D*π-, and "D**"π- with a missing mass method, based on a sample of 231×106 Υ(4S)→BB̄ pairs collected by the BABAR detector at the PEP-II e+e- collider. One of the B mesons is fully reconstructed and the other one decays to a reconstructed charged π and a companion charmed meson identified by its recoil mass, inferred by kinematics. Here "D**" refers to the sum of all the nonstrange charm meson states with masses in the range 2.2-2.8GeV/c2. We measure the branching fractions: B(B-→D0π-)=(4.49±0.21±0.23) ×10-3, B(B-→D*0π-)=(5.13±0.22±0.28)×10- 3, B(B-→"D**0"π-)=(5.50±0.52±1.04) ×10-3, B(B̄0→D+π-)=(3.03±0.23±0.23)×10-3, B(B̄0→D*+π-)=(2.99±0.23±0.24)×10-3, B(B̄0→"D**+"π-)=(2.34±0.65±0. 88)×10-3, and their ratios. © 2006 The American Physical Society.

Four B + →J/ψpΛ̄ candidates in a data set of (88.9±1.0) X 10 6 Y(4S) decays were observed. The probability of the expected charged B background 0.21±0.14 events, producing ≥4 events was 2.5X10 -4 . The branching fraction is (12 -6 +9 )X10 -6 , where the uncertainty includes both statistical and systematic components.

We report on a search for the lepton-flavor-violating processes e+e-→μ+τ- and e+e-→e+τ-. The data sample corresponds to an integrated luminosity of 211fb-1 recorded by the BABAR experiment at the SLAC PEP-II asymmetric-energy B Factory at a center-of-mass energy of s=10.58GeV. We find no evidence for a signal and set the 90% confidence level upper limits on the cross sections to be σμτ<3.8fb and σeτ<9.2fb. The ratio of the cross sections with respect to the dimuon cross section are measured to be σμτ/σμμ<3.4×10-6 and σeτ/σμμ<8.2×10-6. © 2007 The American Physical Society.

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.

We study the decay B0→D*+D*-KS0 using (230±2) ×106BB̄ pairs collected by the BABAR detector at the PEP-II B factory. We measure a branching fraction B(B0→D*+D*-KS0)=(4. 4±0.4±0.7)×10-3 and find evidence for the decay B0→D*-Ds1+(2536) with a significance of 4.6σ. A time-dependent CP asymmetry analysis is also performed to study the possible resonant contributions to B0→D*+D*-KS0 and the sign of cos2β. Our measurement indicates that there is a sizable resonant contribution to the decay B0→D*+D*-KS0 from an unknown Ds1+ state with large width, and that cos2β is positive at the 94% confidence level under certain theoretical assumptions. © 2006 The American Physical Society.

We report the observation of e+e-→η near s=10.58GeV with 6.5σ significance in the K+K-γγ final state in a data sample of 224fb-1 collected by the BABAR experiment at the PEP-II e+e- storage rings. We measure the restricted radiation-corrected cross section to be σ(e+e-→η)=2.1±0.4(stat)±0.1(syst)fb within the range |cosθ*|<0.8, where θ* is the center-of-mass polar angle of the meson. The meson is required to be in the invariant mass range of 1.008

We present measurements of the total production rates and momentum distributions of the charmed baryon Λc+ in e+e-→hadrons at a center-of-mass energy of 10.54 GeV and in Υ(4S) decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in e+e-→cc̄ events, allowing direct studies of c-quark fragmentation. We measure a momentum distribution for Λc+ baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of xp=0.574±0.009 and a total rate of NΛcqq̄=0.057±0.002(exp.)±0.015(BF)Λc+ per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, pK-π+. In Υ(4S) decays we measure a total rate of NΛcΥ=0.091±0. 006(exp.)±0.024(BF) per Υ(4S) decay, and find a much softer momentum distribution than expected from B decays into a Λc+ plus an antinucleon and one to three pions. © 2007 The American Physical Society.