Malcolm John

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.

Abstract:

We search for the rare leptonic decay B+→τ+ντ in a sample of 232×106 BB̄ pairs collected with the BABAR detector at the SLAC PEP-II B-Factory. Signal events are selected by examining the properties of the B meson recoiling against the semileptonic decay B-→D*0-ν̄. We find no evidence for a signal and set an upper limit on the branching fraction of B(B+→τ+ντ)<2.8×10-4 at the 90% confidence level. We combine this result with a previous, statistically independent BABAR search for B+→τ+ντ to give an upper limit of B(B+→τ+ντ)<2.6×10-4 at the 90% confidence level. © 2006 The American Physical Society.

Abstract:

We present the results of a search for the decay B0→τ+τ- in a data sample of (232±3)×106 Υ(4S)→BB̄ decays using the BABAR detector. Certain extensions of the standard model predict measurable levels of this otherwise rare decay. We reconstruct fully one neutral B meson and seek evidence for the signal decay in the rest of the event. We find no evidence for signal events and obtain B(B0→τ+τ-)<4.1×10-3 at the 90% confidence level. © 2006 The American Physical Society.

Abstract:

We present branching fraction measurements of 12 B meson decays of the form B→D(*)Ds(J)(*). The results are based on Υ(4S) decays in BB̄ pairs. One of the B mesons is fully reconstructed and the other decays to two charm mesons, of which one is reconstructed, and the mass and momentum of the other is inferred by kinematics. Combining these results with previous exclusive branching fraction measurements, we determine B(Ds-→ π-)=(4.62±0.36stat.±0.51syst.)%, B(DsJ(2460)-→Ds*- π0)=(56±13stat.±9syst.)% and B(DsJ(2460)-→Ds-γ)= (16±4stat.±3syst.)%. © 2006 The American Physical Society.

Abstract:

The e+e-→pp̄ cross section is determined over a range of pp̄ masses, from threshold to 4.5GeV/c2, by studying the e+e-→pp̄γ process. The data set corresponds to an integrated luminosity of 232fb-1, collected with the BABAR detector at the PEP-II storage ring, at an e+e- center-of-mass energy of 10.6 GeV. The mass dependence of the ratio of electric and magnetic form factors, |GE/GM|, is measured for pp̄ masses below 3GeV/c2; its value is found to be significantly larger than 1 for masses up to 2.2GeV/c2. We also measure J/ψ→pp̄ and ψ(2S)→pp̄ branching fractions and set an upper limit on Y(4260)→pp̄ production and decay. © 2006 The American Physical Society.