Measurement of the B0^0 and B+^+ meson lifetimes with fully reconstructed hadronic final states

The B0 and B+ meson lifetimes have been measured in e+e- annihilation data collected in 1999 and 2000 with the BABAR detector at center-of-mass energies near the Upsilon(4S) resonance. Events are selected in which one B meson is fully reconstructed in a hadronic final state while the second B meson is reconstructed inclusively. A combined fit to the B0 and the B+ decay time difference distributions yields tau_{B0} = 1.546 +/- 0.032 (stat) +/- 0.022(syst) ps, tau_{B+} = 1.673 +/- 0.032 (stat) +/- 0.023 (syst) ps and tau_{B+} / tau_{B0} = 1.082 +/- 0.026 (stat) +/- 0.012 (syst

Precise measurement of the b quark fragmentation function in Z0 boson decays

We have developed a new technique for inclusive reconstruction of the energy of B hadrons. The excellent efficiency and resolution of this technique allow us to make the most precise determination of the b-quark fragmentation function, using e+e-→Z0 decays recorded in the SLAC Large Detector experiment. We compared our measurement with the predictions of a number of fragmentation models. We excluded several of these models and measured the average scaled energy of weakly decaying B hadrons to be (xB) = 0.714 ± 0.005(stat) ± 0.007(syst) ± 0.002 (model dependence). © 2000 The American Physical Society

Measurement of branching fractions for exclusive B decays to charmonium final states

We report branching fraction measurements for exclusive decays of charged and neutral B mesons into two-body final states containing a charmonium meson. We use a sample of 22.72 +/- 0.36 million B anti-B events collected between October 1999 and October 2000 with the BABAR detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. The charmonium mesons considered here are J/psi, psi(2S), and chi_c1, and the light meson in We report branching fraction measurements for exclusive decays of charged and neutral B mesons into two-body final states containing a charmonium meson. We use a sample of 22.72 +/- 0.36 million B anti-B events collected between October 1999 and October 2000 with the BABAR detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. The charmonium mesons considered here are J/psi, psi(2S), and chi_c1, and the light meson in the decay is either a K, K^*, or pi^0. the decay is either a K, K^*, or pi^0

Measurement of the B→J/ψK∗(892)B \rightarrow J/\psi K*(892) decay amplitudes

We present a measurement of the decay amplitudes in B-->J/psi K^*(892) channels using 20.7 fb-1 of data collected at the Upsilon(4S) resonance with the BABAR detector at PEP-II. We measure a P-wave fraction R_perp = (16.0+/-3.2+/-1.4)% and a longitudinal polarization fraction (59.7+/-2.8+/-2.4)%. The measurement of a relative phase that is neither 0 nor pi, phi_ll = 2.50+/-0.20+/-0.08 radians, favors a departure from the factorization hypothesis. Although the decay B-->J/psi Kpi proceeds mainly via K^*(892), there is also evidence for K^*_2(1430) and Kpi S-wave contributions

Measurement of branching fractions and search for CP-violating charge asymmetries in charmless two-body B decays into pions and kaons

We present measurements of the branching fractions and a search for CP-violating charge asymmetries in charmless hadronic decays of B mesons into two-body final states of kaons and pions. The results are based on a data sample of approximately 23 million BB(bar) pairs collected by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. We find the following branching fractions: BF(B0-->pi+pi-)= (4.1+/-1.0+/-0.7) x 10^{-6}, BF(B0-->K+pi-)=(16.7+/-1.6+/-1.3) x 10^{-6}, BF(B+-->K+pi0)=(10.8^{+2.1}_{-1.9}+/-1.0) x 10^{-6}, BF(B+-->K0pi+)=(18.2^{+3.3}_{-3.0}+/-2.0) x 10^{-6}, BF(B0-->K0pi0)=(8.2^{+3.1}_{-2.7}+/-1.2) x 10^{-6}. We also report the 90% confidence level upper limits BF(B0-->K+K-) pi+pi0) anti-K0K+) < 2.4 x 10^{-6}. In addition, charge asymmetries have been measured and found to be consistent with zero, where the statistical precision is in the range of +/-0.10 to +/-0.18, depending on the decay mode

Measurement of J/ψJ/\psi production in continuum e+e−e^{+}e^{-} annihilations near s=10.6−GeV\sqrt{s}=10.6-GeV

The production of $J/\psi$ mesons in continuum $e^+e^-$ annihilations has been studied with the BABAR detector at energies near the $\Upsilon(4S)$ resonance, approximately 10.6 GeV. The mesons are distinguished from $J/\psi$ production in B decays through their center-of-mass momentum and energy. We measure the cross section $e^+e^-\to J/\psi X$ to be $2.52\pm 0.21\pm 0.21$ pb; for momentum above 2 GeV/c, it is $1.87\pm 0.10\pm 0.15$ pb. We set a 90% confidence level upper limit on the branching fraction for direct $\Upsilon(4S)$\to J/\psi X$decays at$4.3\times 10^{-4}$

Study of CP-violating asymmetries in B0→π+π−,K+π−B^0 \to \pi^+\pi^-, K^+\pi^- decays

We present a measurement of the time-dependent CP-violating asymmetries in neutral B decays to the $\pi^+\pi^-$ CP eigenstate, and an updated measurement of the charge asymmetry in $B^0\to K^+\pi^-$ decays. In a sample of 33 million $\Upsilon(4S)\to B\bar B$ decays collected with the BABAR detector at the SLAC PEP-II asymmetric $B$ Factory, we find $65^{+12}_{-11}$ $\pi^+\pi^-$ and $217\pm 18$ $K^+\pi^-$ candidates and measure the asymmetry parameters $S_{\pi\pi} = 0.03^{+0.53}_{-0.56}\pm 0.11$, $C_{\pi\pi} = -0.25^{+0.45}_{-0.47}\pm 0.14$, and ${\cal A}_{K\pi} = -0.07 \pm 0.08 \pm 0.02$, where the first error is statistical and the second is systematic