LHCb

Abstract:

Branching fraction measurements using B-meson decays to Ks ⁰π⁺π^- are presented. These measurements were obtained by analyzing a data sample of 88.9 × 10⁶ Υ(45) → BB̄ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. Using a maximum likelihood fit, the following branching fraction results were obtained: B(B⁰π ⁺π^-) = (43.7 ± 3.8 ± 3.4) × 10 ^-6, B(B⁰ → K*⁺π^-) (12.9 ± 2.4 ± 1.4) × 10^-6, and B(B⁰ → D^-(→Ks ⁰π⁺π ^-)π⁺) = (42.7 ± 2.1 ± 2.2) × 10^-6. The CP violating charge asymmetry AK*π for the decay B⁰ → K*⁺π^- was measured to be AK*π = 0.23 ± 0.18-0.06 ^+0.09. For all these measurements the first error is statistical and the second is systematic.

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⁺ → a0 ⁰π⁺) < 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:

Oscillations in the Bs⁰-Bs⁰ system were studied in events selected from about 4.3 million hadronic Z ⁰ decays registered by DELPHI between 1992 and 2000. This paper presents updates of two published analyses ([11,12]). The first analysis, which utilizes leptons emitted with large momentum transverse to a jet, was improved by means of a better algorithm for the vertex reconstuction and a new algorithm for flavour-tagging at production time. The second analysis, which utilizes Ds-lepton events, was improved by optimizing the treatment of proper time resolution. No signal of B⁰ oscillations was observed and limits on the mass difference between the physical B⁰ states were obtained to be: δms > 8.0ps^-1 at the 95% C.L. with a sensitivity of δms = 9.1 ps^-1 in the high pt lepton analysis and δms < 4.9 ps-1 at the 95% C.L. with a sensitivity of δms = 8.6 ps^-1 in the D s-lepton analysis. Previously published results on these analyses are superseded. The combination of these results with those obtained in other independent analyses previously performed in DELPHI (Ds-hadron, exclusive Bs⁰, inclusive vertex) gives: δm, > 8.5 ps^-1 at the 95% C.L. with a sensitivity of δms = 12.0 ps-1.