Measurement of the $\bar{B}\to X_s\gamma$ Branching Fraction with a Sum of Exclusive Decays

Abstract

We use 772$\times 10^6$ $B\bar{B}$ meson pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector to measure the branching fraction for $\bar{B}\to X_s\gamma$. Our measurement uses a sum-of-exclusives approach in which 38 of the hadronic final states with strangeness equal to $+1$, denoted by $X_s$, are reconstructed. The inclusive branching fraction for $M_{X_s}<$ 2.8 GeV/$c^2$, which corresponds to a minimum photon energy of 1.9 GeV, is measured to be $\mathcal{B}(\bar{B}\to X_s\gamma )=(3.51\pm 0.17\pm 0.33)\times 10^{-4}$, where the first uncertainty is statistical and the second is systematic.

Comments: 13 pages, 21 figures, submitted to PRD