Malcolm John

Abstract:

We report on a search for the rare decay B̄0→D*0γ, which in the standard model is dominated by W-exchange. The analysis is based on a data sample comprising 87.8×106 BB̄ pairs collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. No significant signal is observed, and an upper limit on the branching fraction of 2.5×10-5 at the 90% confidence level is obtained. © 2005 The American Physical Society.

Abstract:

We present an analysis of exclusive charmless semileptonic B-meson decays based on 83×106 BB̄ pairs recorded with the BABAR detector at the Υ(4S) resonance. Using isospin symmetry, we measure branching fractions B(B0→π- +ν)=(1.38±0.10±0.16±0.08)×10-4 and B(B0→ρ- +ν)=(2.14±0.21±0.48±0.28)×10-4, where the errors are statistical, experimental systematic, and due to form-factor shape uncertainties. We compare the measured distribution in q2, the momentum-transfer squared, with theoretical predictions for the form factors from lattice QCD and light-cone sum rules, and extract the Cabibbo-Kobayashi- Maskawa (CKM) matrix element |Vub|=(3.82±0.14±0.22±0.11-0. 52+0.88)×10-3 from B→π ν, where the fourth error reflects the uncertainty of the form-factor normalization. © 2005 The American Physical Society.

Abstract:

We study e+e-→J/ψcc̄ by measuring the invariant mass distribution recoiling against fully reconstructed J/ψ decays, using 124fb-1 of data collected at a center-of-mass energy of 10.6 GeV with the BABAR detector. We observe signals for ηc(1S), χc0, and ηc(2S) in the recoil mass distribution, thus confirming previous measurements. We measure σ(e+e-→J/ψ+cc̄)B(cc̄→>2charged) to be 17.6±2.8(stat)-2.1+1.5(syst)fb, 10.3±2.5(stat)-1.8+1.4(syst)fb, and 16.4±3.7(stat)-3.0+2.4(syst)fb with cc̄=ηc(1S), χc0, and ηc(2S), respectively. © 2005 The American Physical Society.

Abstract:

We present a measurement of the parameters of the Υ(10580) resonance based on a dataset collected with the BABAR detector at the SLAC PEP-II asymmetric B factory. We measure the total width Γtot=(20.7±1. 6±2.5)MeV, the electronic partial width Γee=(0.321±0. 017±0.029)keV and the mass M=(10579.3±0.4±1.2)MeV/c2. © 2005 The American Physical Society.

Abstract:

We search for B-→D0K- and B-→D*0K- and charge conjugates. Here the symbol D0 indicates decay of a D0 or D̄0 into K+π-, while the symbol D*0 indicates decay of a D*0 or D̄*0 to D0π0 or D0γ. These final states can be reached through the b→c transition B-→D(*)0K- followed by the doubly Cabibbo-Kobayashi-Maskawa (CKM)-suppressed D0→K+π-, or the b→u transition B-→D̄(*)0K- followed by the CKM-favored D̄0→K+π-. The interference of these two amplitudes is sensitive to the angle γ of the unitarity triangle. Our results are based on 232×106 Υ(4S)→BB̄ decays collected with the BABAR detector at SLAC. We find no significant evidence for these decays. We set a limit rB|A(B-→D̄0K-)/A(B-→D0K-)|<0.23 at 90% C.L. using the most conservative assumptions on the values of the CKM angle γ and the strong phases in the B and D decay amplitudes. In the case of the D* we set a 90% C.L. limit rB*2|A(B-→D̄*0K-)/A(B-→D*0K-) |2<(0.16)2 which is independent of assumptions on γ and strong phases. © 2005 The American Physical Society.