Malcolm John

Abstract:

We present results of searches for 5-meson decays to K+π -π+ with the BABAR detector. With a data sample of 61.6 × 106 BB̄ pairs, we measure the branching fractions and 90% confidence-level upper limits averaged over charge-conjugate states (the first error is statistical and the second is systematic): B[B+ → K*0(892)π+] = (15.5 ± 1.8 -4.0+1.5) × 10-6, B[B+ → f0(980)K+, f0 → π+π -] = (9.2 ± 1.2-2.6+2.1) × 10 -6, B[B+ → D̄0π+, D̄0 → K+π-] = (184.6 ± 3.2 ± 9.7) × 10-6, B[B+ → ρ0(770)K+] < 6.2 × 10-6 and B[B+ → K+π-π+ nonresonant] < 17 × 10-6.

Abstract:

We present a search for B decays to charmless final states involving charged or neutral a0 mesons. The data sample corresponds to 89 × 106 BB̄ pairs collected with the BABAR detector operating at the PEP-II asymmetric-energy B Factory at Stanford Linear Accelerator Center. We find no significant signals and determine the following 90% C.L. upper limits: B(B0 → a0-π+) < 5.1 × 10-6, B(B0 → a0-K+) < 2.1 × 10-6, B(B- → a0-K̄0) < 3.9 × 10-6, B(B+ → a00π+) < 5.8 × 10-6, B(B+ → a00K+) < 2.5 × 10-6, and B(B0 → a00K0) < 7.8 × 10-6, where in all cases B indicates the product of branching fractions for B → a0X and a0 ηπ, where X indicates K or π.

Abstract:

Based on an 87-fb-1 data set collected by the BABAR detector at the PEP-II asymmetric-energy B Factory, a search for D0- D̄0 mixing has been made using the semileptonic decay modes D*+ → π+D0, D0 → K(*)eν (+c.c.). The use of these modes allows unambiguous flavor tagging and a combined fit of the D0 decay time and D*+-D0 mass difference (ΔM) distributions. The high-statistics sample of unmixed semileptonic D0 decays is used to model the ΔM distribution and time dependence of mixed events directly from the data Neural networks are used to select events and reconstruct the D0. A result consistent with no charm mixing has been obtained, Rmix = 0.0023 ± 0.0012 ± 0.0004. This corresponds to an upper limit of Rmix < 0.0042 (90% C.L.).

Abstract:

The process e+ e- → π+ π- π0 γ has been studied at a center-of-mass energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with the BABAR detector at the PEP-II collider. From the measured 3π mass spectrum we have obtained the products of branching fractions for the ω and φ mesons, B(ω → e+ e-) B(ω → 3π) = (6.70 ± 0.06 ± 0.27) × 10 -5 and B(φ → e+e-)B(φ → 3π) = (4.30 ± 0.08 ± 0.21) × 10-5 and evaluated the e+ e- → π+ π- π0 cross section for the e+ e - center-of-mass energy range 1.05 to 3.00 GeV. About 900 e + e- → J/ψγ → π+ π- π0 γ events have been selected and the branching fraction B(J/ψ → π+ π- π0) = (2.18 ± 0.19)% has been measured.