Malcolm John

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.

Abstract:

We present a measurement of the branching fraction and time-dependent CP asymmetry of B0→ρ0K0. The results are obtained from a data sample of 227×106 Υ(4S)→BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at Stanford Linear Accelerator Center. From a time-dependent maximum likelihood fit yielding 111±19 signal events, we find B(B0→ρ0K0)=(4.9±0.8±0.9)×10-6, where the first error is statistical and the second systematic. We report the measurement of the CP parameters Sρ0KS0=0.20±0.52±0.24 and Cρ0KS0=0.64±0.41±0.20. © 2007 The American Physical Society.

Abstract:

We present an observation of B→η′K*. The data sample corresponds to 232×106 BB̄ 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(B0→η′K*0)=3.8±1.1±0.5 and B(B+→η′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→η′K* with B(B→η′K*)= 4.1-0.9+1.0±0.5. We also search for B→η′ρ and η′f0(980)(f0→π+π-) with results and 90% confidence level upper limits B(B+→η′ρ+)=8.7-2.8-1.3+3.1+2.3 (<14), B(B0→η′ρ0)<3.7, and B(B0→η′f0(980) (f0→π+π-))<1.5. Charge asymmetries in the channels with significant yields are consistent with zero. © 2007 The American Physical Society.

Abstract:

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)→BB̄ 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, B(B0→K+K-nγ;Eγmax =59MeV)<0.5×10-6(90%confidence level), where the first uncertainty is statistical and the second is systematic. Theoretical calculations can be used to extrapolate from the above measurements the nonradiative branching fractions, B0. Using one such calculation, we find: B0(B0→π+π-)=(5.5±0. 4±0.3)×10-6, B0(B0→K+π-)=(19.1±0.6±0.6) ×10-6, B0(B0→K+K-)<0.5×10-6(90%confidence level). Meaningful comparison between theory and experiment, as well as combination of measurements from different experiments, can be performed only in terms of these nonradiative quantities. © 2007 The American Physical Society.