Branching Fraction and Photon Energy Spectrum b -> s gamma

TL;DR

This paper reports precise measurements of the branching fraction and photon energy spectrum for the b -> s gamma decay, providing insights into the Standard Model and Heavy Quark Effective Theory parameters.

Contribution

The study presents the first and second moments of the photon energy spectrum and extracts the HQET parameter Lambda[Bar] from experimental data.

Findings

BR(b -> s gamma) = (3.21 +- 0.43 +- 0.27 +0.18 -0.10) x 10^(-4)

First moment of photon energy: 2.346 +- 0.032 +- 0.011 GeV

HQET parameter Lambda[Bar] = 0.35 +- 0.08 +- 0.10 GeV

Abstract

We have measured the branching fraction and photon energy spectrum for the radiative penguin process b -> s gamma. We find BR(b -> s gamma) = (3.21 +- 0.43 +- 0.27 +0.18 -0.10) 10^(-4), where the errors are statistical, systematic, and from theory corrections. We obtain first and second moments of the photon energy spectrum above 2.0 GeV, < E_\gamma > = 2.346 +- 0.032 +- 0.011 GeV, and <E^2_gamma> - <E_gamma>^2 = 0.0226 +- 0.0066 +- 0.0020 GeV^2, where the errors are statistical and systematic. From the first moment we obtain (in MS[Bar], to order 1/M^3 and beta_0 alpha_s^2) the HQET parameter Lambda[Bar] = 0.35 +- 0.08 +- 0.10 GeV.