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

Le résumé fourni par la source

Using 88.9 million B{bar B} events collected by the BABAR detector at the {Upsilon}(4S), they measure the branching fraction for the radiative penguin process B {yields} X{sub s}{gamma} from the sum of 38 exclusive final states. The inclusive branching fraction above a minimum photon energy E{sub {gamma}} > 1.9 GeV is {Beta}(b {yields} s{gamma}) = (3.27 {+-} 0.18(stat.){sub -0.40}{sup +0.55}(syst.){sub -0.09}{sup +0.04}(theory)) x 10{sup -4}. They also measure the isospin asymmetry between B{sup -} {yields} X{sub s{bar u}}{gamma} and {bar B}{sup 0} {yields} X{sub sd}{gamma} to be {Delta}{sub 0-} = -0.006 {+-} 0.058(stat.) {+-} 0.009(syst.) {+-} 0.024({bar B}{sup 0}/B{sup -}). 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 m{sub b} and {mu}{sub {pi}}{sup 2}. The fitted parameters are consistent with those obtained from semileptonic B {yields} X{sub c}{ell}{nu} decays, and are useful inputs for the extraction of |V{sub ub}| from measurements of semileptonic B {yields} X{sub u}{ell}{nu} decays.

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