Physics
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Item Radiative B Meson Decay as a Probe of Physics Beyond the Standard Model: Time-Dependent CP Violation in B0 → KS π0 γ and the B → φ K γ Branching Fraction(2008) Tuggle, Joseph M.; Jawahery, Abolhassan; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)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.Item Measurements of the CP Content and CP Violating Asymmetries in Neutral B Decays to Two D* Mesons with the BaBar Detector(2004-04-12) Lillard, Vincent; Roberts, Douglas; PhysicsThis dissertation presents a measurement of time-dependent CP-violating asymmetries and a measurement of the CP-odd parity fraction in the decay B0 -> D*+D*-. The measurements are derived from a data sample of 88 x 10^6 BBbar pairs collected by the BaBar detector at the PEP-II asymmetric-energy B Factory located at the Stanford Linear Accelerator Center. A one-dimensional angular analysis of the decay products measures the CP-odd fraction to be 0.063 +/- 0.055(stat) +/- 0.009(syst), indicating that the D*+D*- final state is mostly CP-even. The time-dependent CP asymmetry parameters Im(lambda_+) and |lambda_+| are determined from an analysis of the time-dependence of flavor-tagged B decays. One neutral B meson is fully reconstructed in a D*+D*- final state, while the other B is inclusively reconstructed in order to determine its flavor. The Standard Model predicts the CP asymmetry parameters Im(lambda_+) and |lambda_+| to be -sin(2beta) and 1, respectively, in the absence of penguin diagram contributions. They are determined to be 0.05 +/- 0.29(stat) +/- 0.10(syst) and 0.75 +/- 0.19(stat) +/- 0.02(syst), respectively, which corresponds to a 2.5 sigma deviation from Standard Model predictions with penguin contributions ignored.