Paolo Franchini

Abstract:

A precise measurement of the cross section of the process e+e-→π+π-(γ) from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using 232fb-1 of data collected with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e+e-→μ+μ-γ(γ). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the ππ cross section measured from threshold to 1.8 GeV is (514.1±2.2(stat)±3.1(syst))×10- 10. © 2009 The American Physical Society.

Abstract:

We present an analysis of the decays B⁰ → K^∗0(892)γ and B⁺ → K^∗+(892)γ using a sample of about 383 × 10⁶ BB events collected with the BABAR detector at the PEP-II asymmetric energy B factory. We measure the branching fractions B(B⁰ → K^∗0γ = (4.47 ± 0.10 ± 0.16) × 10^-5 and B(B⁺ → K^∗+ γ) = (4.22 ± 0.14 ± 0.16) × 10^-5. We constrain the direct CP asymmetry to be -0.033 < A(B → K^∗ γ) < 0.028 and the isospin asymmetry to be 0.017 < δ0- < 0.116, where the limits are determined by the 90% confidence interval and include both the statistical and systematic uncertainties.

Abstract:

We present evidence of D0-D̄0 mixing using a time-dependent amplitude analysis of the decay D0→K+π-π0 in a data sample of 384fb-1 collected with the BABAR detector at the PEP-II e+e- collider at the Stanford Linear Accelerator Center. Assuming CP conservation, we measure the mixing parameters xKππ0′=[2.61-0.68+0.57(stat)±0.39(syst)]%, yKππ0′=[-0.06-0.64+0.55(stat)±0.34(syst)]%. This result is inconsistent with the no-mixing hypothesis with a significance of 3.2 standard deviations. We find no evidence of CP violation in mixing. © 2009 The American Physical Society.

Abstract:

We have performed a search for the ηb(1S) meson in the radiative decay of the Υ(2S) resonance using a sample of 91.6×106 Υ(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at Eγ=609.3-4.5+4.6(stat)±1.9(syst)MeV, corresponding to an ηb(1S) mass of 9394.2-4.9+4.8(stat)±2.0(syst)MeV/c2. The branching fraction for the decay Υ(2S)→γηb(1S) is determined to be [3.9±1.1(stat)-0.9+1.1(syst)]×10-4. We find the ratio of branching fractions B[Υ(2S)→γηb(1S)]/B[Υ(3S) →γηb(1S)]=0.82±0.24(stat)-0.19+0.20(syst). © 2009 The American Physical Society.

Abstract:

We search for evidence of a light scalar boson in the radiative decays of the Υ(2S) and Υ(3S) resonances: Υ(2S,3S)→γA0, A0→μ+μ-. Such a particle appears in extensions of the standard model, where a light CP-odd Higgs boson naturally couples strongly to b quarks. We find no evidence for such processes in the mass range 0.212≤mA0≤9.3GeV in the samples of 99×106 Υ(2S) and 122×106 Υ(3S) decays collected by the BABAR detector at the SLAC PEP-II B factory and set stringent upper limits on the effective coupling of the b quark to the A0. We also limit the dimuon branching fraction of the ηb meson: B(ηb→μ+μ-) <0.9% at 90% confidence level. © 2009 The American Physical Society.