Malcolm John

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.

Abstract:

We present a search for the decay of a B0 or B̄0 meson to a K̄*0K0 or K*0K̄0 final state, using a sample of approximately 232×106 BB̄ events collected with the BABAR detector at the PEP-II asymmetric energy e+e- collider at SLAC. The measured branching fraction is B(B0→K̄*0K0)+B(B0→K*0K̄0)=(0.2-0.8- 0.3+0.9+0.1)×10-6. We obtain the following upper limit for the branching fraction at 90% confidence level: B(B0→K̄*0K0) +B(B0→K*0K̄0)<1.9×10-6. We use our result to constrain the standard model prediction for the deviation of the CP asymmetry in B0→K0 from sin2β. © 2006 The American Physical Society.

Abstract:

We present the first search for the decay B0→KS0KS0KL0 using a data sample of 232×106 BB̄ pairs. We find no statistically significant evidence for the nonresonant component of this decay. Our central value for the branching fraction, assuming the true Dalitz distribution is uniform and excluding the resonance, is B(B0→KS0KS0KL0)=(2.4-2.5+2.7±0.6) ×10-6 where the errors are statistical and systematic, respectively. We set a single-sided Bayesian upper limit of B(B0→KS0KS0KL0)<7.4×10- 6 at 90% confidence level using a uniform prior probability for physical values. Assuming the worst-case true Dalitz distribution, where the signal is entirely in the region of lowest efficiency, the 90% confidence level upper limit is B(B0→KS0KS0KL0)<16×10-6. © 2006 The American Physical Society.

Abstract:

A search for the decay of the τ lepton to five charged and two neutral pions is performed using data collected by the BABAR detector at the PEP-II asymmetric-energy e+e- collider. The analysis uses 232fb-1 of data at center-of-mass energies on or near the Υ(4S) resonance. We observe 10 events with an expected background of 6.5-1.4+2.0 events. In the absence of a signal, we set the limit on the branching ratio B(τ-→3π- 2π+2π0ντ)<3.4×10-6 at the 90% confidence level. This is a significant improvement over the previously established limit. In addition, we search for the decay mode τ-→2ωπ-ντ. We observe 1 event with an expected background of 0.4+1.0-0.4 events and calculate the upper limit B(τ-→2ωπ-ντ)<5.4×10-7 at the 90% confidence level. This is the first upper limit for this mode. © 2006 The American Physical Society.