Measurements of the Branching Fraction, CP Asymmetry And Isospin Asymmetry of the Radiative Penguin B0 ---> K*0 Gamma And a Search for the Decays B0 ---> Rho Gamma And B0 ---> Omega Gamma at BaBar

Measurements of the branching fraction, CP asymmetry and isospin asymmetry of the radiative penguin decay B → Kγ and a search for the decays B → ργ and B → ωγ at BABAR by Patrick Michael Spradlin Radiative penguin decays of B mesons provide a fertile ground for precision tests of the Standard Model. Because such decays must proceed through 1-loop or higher processes in Standard Model perturbation theory, they are quite rare and their amplitudes are particularly susceptible to interference from physics beyond the Standard Model. This thesis presents measurements carried out at the BABAR experiment of the branching fraction B, CP asymmetry parameter ACP and isospin asymmetry parameter ∆0− of the radiative penguin decay B → K∗0γ. The results of these measurements are B(B → K∗0γ) = (3.92± 0.20± 0.24)× 10−5 ACP (B → K∗γ) = −0.013± 0.036± 0.010 ∆0−(B → K∗γ) = 0.050± 0.045± 0.037. The measurements are consistent with Standard Model predictions, but do not rule out future discovery of non-Standard Model deviations with an enlarged data set. This thesis also presents a related search for the radiative penguin decays B → ργ, B → ργ and B → ωγ. These decays have yet to be observed at any experiment. This analysis sets 90% confidence upper limits on their branching fractions of B(B → ργ) < 0.4× 10−6 B(B → ργ) < 1.8× 10−6 B(B → ωγ) < 1.0× 10−6 B(B → (ρ/ω)γ) < 1.2× 10−6 , where B(B → (ρ/ω)γ) is a combined limit from a search for decays in any of the three modes. The B(B → (ρ/ω)γ) measurement assumes theoretical isospin relationships among B(B0 → ργ), B(B+ → ργ), and B(B0 → ωγ). The ratio of the branching fractions B(B → (ρ/ω)γ) and B(B → K∗γ) are related to the CKM matrix ratio |Vtd/Vts|. The measurements presented in this thesis give a 90% confidence level upper limit of |Vtd/Vts| < 0.190.