Measurement of the B --> K^* gamma Branching Fractions and Asymmetries

TL;DR

This paper reports precise measurements of the branching fractions and asymmetries in the radiative decay B --> K^* gamma, using data from the Belle detector, providing insights into flavor physics and CP violation.

Contribution

First measurement of B --> K^* gamma branching fractions and asymmetries using Belle data, improving precision and testing Standard Model predictions.

Findings

Branching fractions measured as (4.01 ± 0.21 ± 0.17)×10^{-5} and (4.25 ± 0.31 ± 0.24)×10^{-5}

Isospin asymmetry Δ_{0+} = +0.012 ± 0.044 ± 0.026

CP asymmetry A_{cp} = 0.015 ± 0.044 ± 0.012

Abstract

We report measurements of the radiative decay B --> K^*\gamma. The analysis is based on a data sample containing 85.0*10^6 B meson pairs collected by the Belle detector at the KEKB storage ring. We measure branching fractions of Br(B^0 --> K^{*0}\gamma) = (4.01 \pm 0.21 \pm 0.17)*10^{-5} and Br(B^+ --> K^{*+}\gamma) = (4.25 \pm 0.31 \pm 0.24)*10^{-5}, where the first and second errors are statistical and systematic, respectively. The isospin asymmetry between B^0 and B^+ decay widths is measured to be \Delta_{0+} = +0.012 \pm 0.044 \pm 0.026. We search for a partial rate asymmetry between CP conjugate modes, and find A_{cp}(B --> K^*\gamma) = =0.015 \pm 0.044 \pm 0.012.