Radiative B Meson Decay as a Probe of Physics Beyond the Standard Model: Time-Dependent CP Violation in B<super>0</super> &rarr; K_S &pi;<super>0</super> &gamma; and the B &rarr; &phi; K &gamma; Branching Fraction

Abstract

I present measurements of radiative B meson decays to the final states KS π0 γ and K φ γ based on data collected at the Υ(4S) resonance with the BaBar detector at the PEP-II e+e– collider at SLAC. In a data sample of 467 million BBbar pairs, the time-dependent CP asymmetry in B0 → KS π0 γ decays is measured in two regions of KS-π0 invariant mass. In the K* region, 0.8 < m(KS π0) < 1.0 GeV/c2, we find SK* γ = –0.03 ± 0.29 ± 0.03 and CK* γ = –0.14 ± 0.16 ± 0.03; in the range 1.1 < m(KS π0) < 1.8 GeV/c2, we find SKS π0 γ = –0.78 ± 0.59 ± 0.09 and CKS π0 γ = –0.36 ± 0.33 ± 0.04. With a sample of 228 million BBbar pairs we measure the branching fraction B(B+ → K+ φ γ) = (3.5 ± 0.6 ± 0.4) × 10–6 and set the limit B(B0 → K0 φ γ) < 2.7 × 10–6 at 90% confidence level. The direct CP asymmetry in B+ → K+ φ γ is found to be ACP = (–26 ± 14 ± 5)%. In each case the uncertainties are statistical and systematic, respectively.