Determination of the Branching Fraction for Inclusive Decays B -> X_{s} gamma

TL;DR

This paper reports a preliminary measurement of the inclusive branching fraction for the rare decay B -> X_s gamma using data from the BaBar detector, reducing background with a novel tagging method, and finds results consistent with the Standard Model.

Contribution

First measurement of B -> X_s gamma branching fraction using a tagging method that minimizes model dependence and background, based on 60 million BB pairs.

Findings

Branching fraction measured as (3.88 +- 0.36 (stat) +- 0.37 (sys) +0.43-0.23 (model)) x 10^{-4}.

Result consistent with Standard Model predictions.

Provides constraints on new physics contributions to B decays.

Abstract

We present a preliminary determination of the inclusive branching fraction for the rare radiative penguin transition B -> X_{s} gamma. The measurement is based on a data sample of 60 million BB pairs collected between 1999 and 2001 with the BaBar detector at the PEPII asymmetric-energy e+e- B Factory at SLAC. We study events containing a high-energy photon from one B (or Bbar) decay and a tagging primary lepton from the decay of the other B meson. By this means, we are able to reduce a significant component of the background without introduction of model dependent uncertainties in the event selection efficiency. We determine the branching fraction BR(B->X_{s} gamma)=3.88 +-0.36(stat.)+-0.37(sys.) +0.43-0.23(model.)x10^{-4}, which is consistent with Standard Model predictions and provides a constraint on possible new physics contributions to the electromagnetic penguin amplitude in B decays.