Malcolm John

Abstract:

A Dalitz plot analysis of approximately 12500 D0 events reconstructed in the hadronic decay D0→K̄0K+K- is presented. This analysis is based on a data sample of 91.5fb-1 collected with the BABAR detector at the PEP-II asymmetric-energy e+e- storage rings at SLAC running at center-of-mass energies on and 40 MeV below the Υ(4S) resonance. The events are selected from e+e-→cc̄ annihilations using the decay D*+→D0π+. The following ratio of branching fractions has been obtained: BR= Γ(D0→K̄0K+K-)Γ(D0→K̄0π+π-)=(15.8±0. 1(stat.)±0.5(syst.))×10-2. Estimates of fractions and phases for resonant and nonresonant contributions to the Dalitz plot are also presented. The a0(980)→K̄K projection has been extracted with little background. A search for CP asymmetries on the Dalitz plot has been performed. © 2005 The American Physical Society.

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:

A search for the decay of the τ lepton to seven charged pions and one or zero π0 mesons was performed using the BABAR detector at the PEP-II asymmetric-energy e+e- collider. The analysis uses 232.2fb-1 of data at center-of-mass energies on or near the Υ(4S) resonance. We observe 24 events with an expected background of 21.6±1.3 events. Without evidence for a signal, we calculate an upper limit of B(τ-→4π-3π+(π0) ντ)<3.0×10-7 at 90% confidence level. This is an improvement by nearly an order of magnitude over the previously established limit. In addition, we set upper limits for the exclusive decays τ-→4π-3π+ντ and τ-→4π-3π+π0ντ. © 2005 The American Physical Society.

Abstract:

We report on the search for the rare decays B+→D(*)+KS0 in approximately 226×106 Υ(4S)→BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We do not observe any significant signal and we set 90% confidence-level upper limits on the branching fractions, B(B+→D+K0)<0.5×10-5 and B(B+→D*+K0)<0.9×10-5. © 2005 The American Physical Society.