Paolo Franchini

Abstract:

We present a study of B decays into semileptonic final states containing charged and neutral D1(2420) and D2*(2460). The analysis is based on a data sample of 208fb-1 collected at the Υ(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. With a simultaneous fit to four different decay chains, the semileptonic branching fractions are extracted from measurements of the mass difference Δm=m(D**)- m(D) distributions. Product branching fractions are determined to be B(B+→D10ℓ+νℓ)×B(D10→D*+π-)=(2.97±0. 17±0.17)×10-3, B(B+→D2*0ℓ+νℓ)×B (D2*0→D(*)+π-)=(2.29±0.23±0.21)×10-3, B(B0→D1-ℓ+ν)×B(D1-→D*0π-)=(2.78±0. 24±0.25)×10-3 and B(B0→D2*-ℓ+νℓ) ×B(D2*-→D(*)0π-)=(1.77±0.26±0.11) ×10-3. In addition we measure the branching ratio Γ(D2 *→Dπ-)/Γ(D2*→D(*)π-)=0.62±0. 03±0.02. © 2009 The American Physical Society.

Abstract:

Using a sample of 383×106 BB̄ events collected by the BABAR experiment, we measure sums of seven exclusive final states B→Xd(s)γ, where Xd(Xs) is a nonstrange (strange) charmless hadronic system in the mass range 0.6-1.8GeV/c2. After correcting for unmeasured decay modes in this mass range, we obtain a branching fraction for b→dγ of (7.2±2.7(stat)±2.3(syst))×10-6. Taking the ratio of Xd to Xs we find Γ(b→dγ)/Γ(b→sγ)=0.033±0. 013(stat)±0.009(syst), from which we determine |Vtd/Vts|=0.177±0. 043. © 2009 The American Physical Society.

Abstract:

We present improved measurements of the branching fraction B, the longitudinal polarization fraction fL, and the direct CP asymmetry ACP in the B meson decay channel B+→ρ+ρ0. The data sample was collected with the BABAR detector at SLAC. The results are B(B+→ρ+ρ0)=(23.7±1. 4±1.4)×10-6, fL=0.950±0.015±0.006, and ACP=-0.054±0.055±0.010, where the uncertainties are statistical and systematic, respectively. Based on these results, we perform an isospin analysis and determine the Cabibbo-Kobayashi-Maskawa phase angle α=arg(-VtdVtb*/VudVub*) to be (92.4-6.5+6.0)°. © 2009 The American Physical Society.

Abstract:

In a search for B→cc̄γK decays with the BABAR detector, where cc̄ includes J/ψ and ψ(2S), and K includes K±, KS0, and K*(892), we find evidence for X(3872)→J/ψγ and X(3872)→ψ(2S)γ with 3.6σ and 3.5σ significance, respectively. We measure the product of branching fractions B(B±→ X(3872)K±)×B(X(3872)→J/ψγ)=[2.8±0.8(stat) ±0.1(syst)]×10-6 and B(B±→X(3872)K±) ×B(X(3872)→ψ(2S)γ)=[9.5±2.7(stat)±0.6(syst)] ×10-6. © 2009 The American Physical Society.

Abstract:

We measure branching fractions and integrated rate asymmetries for the rare decays B→K(*)l+l-, where l+l- is either e+e- or μ+μ-, using a sample of 384×106 BB̄ events collected with the BABAR detector at the PEP-II e+e- collider. We find no evidence for direct CP or lepton-flavor asymmetries. However, for dilepton masses below the J/ψ resonance, we find evidence for unexpectedly large isospin asymmetries in both B→Kl+l- and B→K*l+l- which differ, respectively, by 3.2σ and 2.7σ, including systematic uncertainties, from the standard model expectations. © 2009 The American Physical Society.