Malcolm John

Abstract:

We search for the production of doubly charmed baryons in e+e- annihilations at or near a center-of-mass energy of 10.58 GeV, in a data sample with an integrated luminosity of 232fb-1 recorded with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. We search for Ξcc+ baryons in the final states Λc+K-π+ and Ξc0π+, and Ξcc++ baryons in the final states Λc+K-π+π+ and Ξc0π+π+. We find no evidence for the production of doubly charmed baryons. © 2006 The American Physical Society.

Abstract:

A search for the nonconservation of lepton flavor in the decay τ±→e±γ has been performed with 2.07×108 e+e-→τ+τ- events collected by the BABAR detector at the SLAC PEP II storage ring at a center-of-mass energy near 10.58 GeV. We find no evidence for a signal and set an upper limit on the branching ratio of B(τ±→ e±γ)<1.1×10-7 at 90% confidence level. © 2006 The American Physical Society.

Abstract:

We report on searches for B-→Ds- and B-→Ds*-. In the context of the standard model, these decays are expected to be highly suppressed since they proceed through annihilation of the b and ū quarks in the B- meson. Our results are based on 234×106 Υ(4S)→BB̄ decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set Bayesian 90% confidence level upper limits on the branching fractions B(B-→Ds-)<1.9×10-6 and B(B-→Ds*-)<1. 2×10-5. These results are consistent with standard model expectations. © 2006 The American Physical Society.

Abstract:

We search for the charmed pentaquark candidate reported by the H1 collaboration, the Θc(3100)0, in e+e- interactions at a center-of-mass (c.m.) energy of 10.58 GeV, using 124fb-1 of data recorded with the BABAR detector at the PEP-II e+e- facility at SLAC. We find no evidence for such a state in the same pD*- decay mode reported by H1, and we set limits on its production cross section times branching fraction into pD*- as a function of c.m. momentum. The corresponding limit on its total rate per e+e-→qq̄ event, times branching fraction, is about 3 orders of magnitude lower than rates measured for the charmed Λc and Σc baryons in such events. © 2006 The American Physical Society.

Abstract:

We present a search for the rare B-meson decay B0→a1±ρ with a1±→π+π-π±. We use (110±1.2) ×106Υ(4S)→BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We obtain an upper limit of 30×10-6(90%C.L.) for the branching fraction product B(B0→a1± ρ)B(a1±→π+π-π±), where we assume that the a1± decays exclusively to ρ0π±. © 2006 The American Physical Society.