Measurement of Branching Fractions, and CP and Isospin Asymmetries, for $B \to K^* \gamma$

TL;DR

This paper reports precise measurements of branching fractions, CP asymmetry, and isospin asymmetry in B meson decays to K* gamma, providing important tests of the Standard Model and constraints on new physics.

Contribution

The study presents the first measurements of these asymmetries with improved precision using a large data sample from BaBar.

Findings

Branching fraction B(B->K*0,gamma) = (3.92 +/- 0.20 +/- 0.24) x 10^{-5}

Branching fraction B(B->K*+,gamma) = (3.87 +/- 0.28 +/- 0.26) x 10^{-5}

CP asymmetry constrained to -0.74 < A_CP < 0.049

Abstract

The branching fractions of the decays B->K*0,gamma and B->K*+,gamma are measured using a sample of 88 x 10^6 B\bar{B} events collected with the BaBar detector at the PEP-II asymmetric-energy e^+e^- collider. We find B(B->K*0,gamma) = 3.92 +/- 0.20 (stat) +/- 0.24 (syst) x 10^{-5} and B(B->K*_,gamma) = 3.87 +/- 0.28 (stat) +/- 0.26 (syst) x 10^{-5}. Our measurements also constrain the direct $\CP$ asymmetry to be -0.74 < A_{CP}(B->K*,gamma) < 0.049, and the isospin asymmetry to be -0.46 < \Delata_{0-} < 0.146, both at the 90% confidence level.