Malcolm John

Abstract:

We report on a study of inclusive B- and B̄0 meson decays to D0X, D̄0X, D+X, D-X, Ds+X, Ds-X, Λc+X, Λ̄c-X, based on a sample of 231×106 BB̄ events recorded with the BABAR detector at the Υ(4S) resonance. Events are selected by completely reconstructing one B and searching for a reconstructed charm particle in the rest of the event. From the measured branching fractions of these decays, we infer the number of charm and anticharm particles per B̄ decay, separately for charged and neutral parents. We derive the total charm yield per B- decay, nc-=1.208±0. 023±0.040-0.029+0.035, and per B̄0 decay, nc0=1.203±0. 030±0.034-0.035+0.044 where the first uncertainty is statistical, the second is systematic, and the third reflects the charm branching-fraction uncertainties. We also present the charm momentum distributions measured in the B̄ rest frame. © 2007 The American Physical Society.

Abstract:

Using 230.2fb-1 of e+e- annihilation data collected with the BABAR detector at and near the peak of the Υ(4S) resonance, 489±55 events containing the pure leptonic decay Ds+→μ+νμ have been isolated in charm-tagged events. The ratio of partial widths Γ(Ds+→μ+νμ) /Γ(Ds+→ π+) is measured to be 0.143±0.018±0.006 allowing a determination of the pseudoscalar decay constant fDs= (283±17±7±14)MeV. The errors are statistical, systematic, and from the Ds+→ π+ branching ratio, respectively. © 2007 The American Physical Society.

Abstract:

We measure the branching ratios of the Cabibbo-suppressed decays Λc+→ΛK+ and Λc+→Σ0K+ relative to the Cabibbo-favored decay modes Λc+→Λπ+ and Λc+→Σ0π+ to be 0.044±0.004(stat.)±0.003(syst. ) and 0.038±0.005(stat.)±0.003(syst.), respectively. We set an upper limit on the branching ratio at the 90% confidence level for Λc+→ΛK+π+π- of 4.1×10-2 relative to Λc+→Λπ+, and for Λc+→Σ0K+π+π- of 2.0×10-2 relative to Λc+→Σ0π+. We also measure the branching fraction for the Cabibbo-favored mode Λc+→Σ0π+ relative to Λc+→Λπ+ to be 0.977±0.015(stat.) ±0.051(syst.). This analysis was performed using a data sample with an integrated luminosity of 125fb-1 collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. © 2007 The American Physical Society.

Abstract:

We report the observation of decays B0→Ds(*)+π- and B0→Ds(*)-K+ in a sample of 230×106 Υ(4S)→BB̄ events recorded with the BABAR detector at the SLAC PEP-II asymmetric-energy e+e- storage ring. We measure the branching fractions B(B0→Ds+π-)=(1. 3±0.3(stat)±0.2(syst))×10-5, B(B0→Ds-K+)=(2.5±0. 4(stat)±0.4(syst))×10-5, B(B0→Ds*+π-)=(2.8±0. 6(stat)±0.5(syst))×10-5, and B(B0→Ds*-K+)=(2.0±0. 5(stat)±0.4(syst))×10-5. The significances of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is the first observation of B0→Ds+π-, B0→Ds*+π-, and B0→Ds*-K+ decays. © 2007 The American Physical Society.

Abstract:

Using 65×106 Υ(4S)→BB̄ events collected with the BABAR detector at the PEP-II e+e- storage ring at the Stanford Linear Accelerator Center, we measure the color-favored branching fractions B(B̄0→D+π- )=(2.55±0.05±0.16)×10-3, B(B̄0→D*+π-)=(2. 79±0.08±0.17)×10-3, B(B-→D0π-)=(4.90±0. 07±0.22)×10-3 and B(B-→D*0π-)=(5.52±0. 17±0.42)×10-3, where the first error is statistical and the second is systematic. With these results and the current world average for the branching fraction for the color-suppressed decay B̄0→D(*) 0π0, the cosines of the strong phase difference δ between the I=1/2 and I=3/2 isospin amplitudes are determined to be cos δ=0.872-0.007-0.029+0. 008+0.031 for the B̄→Dπ process and cos δ=0.924-0.017-0. 054+0.019+0.063 for the B̄→D*π process. Under the isospin symmetry, the results for cos δ suggest the presence of final-state interactions in the Dπ system. © 2007 The American Physical Society.