Measurements of the B to Xs gamma Branching Fraction and Spectral Shape from a Sum of Exclusive Final States

Using 88.9 million B(bar B) events collected by the BABAR detector at the Υ(4S), they measure the branching fraction for the radiative penguin process B → Xsγ from the sum of 38 exclusive final states. The inclusive branching fraction above a minimum photon energy Eγ > 1.9 GeV is Β(b → sγ) = (3.27 ± 0.18(stat.)-0.40+0.55(syst.)-0.09+0.04(theory)) x 10-4. They also measure the isospin asymmetry between B- → Xs#bar uγ# and (bar B)0 → Xsdγ to be Δ0- = -0.006 ± 0.058(stat.) ± 0.009(syst.) ± 0.024((bar B)0/B-). The photon energy spectrum is measured in the B rest frame, from which moments are derived for different values of the minimum photon energy. They present fits to the photon spectrum and moments which give the heavy-quark parameters mb and μπ2. The fitted parameters are consistent with those obtained from semileptonic B → Xc(ell)ν decays, and are useful inputs for the extraction of |Vub| from measurements of semileptonic B → Xu(ell)ν decays