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By combining a recent estimate of the total {bar B} → X{sub s}[gamma] branching fraction at O([alpha]{sub s}2) with a detailed analysis of the effects of a cut E{sub [gamma]} ≥ 1.6 GeV on photon energy, a prediction for the partial {bar B} → X{sub s}[gamma] branching fraction at next-to-next-to-leading order in renormalization-group improved perturbation theory is obtained, in which contributions from all relevant scales are properly factorized. The result Br({bar B} → X{sub s}{gamma}) = (2.98 ± 0.26) · 10−4 is about 1.4[sigma] lower than the experimental world average. This opens a window for significant New Physics contributions in rare radiative B decays.
The complete two-loop expression for the jet function J(p2, [mu]) of soft-collinear effective theory is presented, including non-logarithmic terms. Combined with our previous calculation of the soft function S([omega], [mu]), this result provides the basis for a calculation of the effect of a photon-energy cut in the measurement of the {bar B} 2!X{sub s}[gamma] decay rate at next-to-next-to-leading order in renormalization-group improved perturbation theory. The jet function is also relevant to the resummation of Sudakov logarithms in other hard QCD processes.
We present a measurement of the branching fraction and photon energy spectrum for the decay B → X{sub s}[gamma] using data from the BABAR experiment. The data sample corresponds to an integrated luminosity of 210 fb−1, from which approximately 680,000 B{bar B} events are tagged by a fully reconstructed hadronic decay of one of the B mesons. In the decay of the second B meson, an isolated high-energy photon is identified. We measure [Beta](B → X{sub s}[gamma]) = (3.66 ± 0.85{sub stat} ± 0.60{sub syst}) x 10−4 for photon energies E{sub {gamma}} above 1.9 GeV in the B rest frame. From the measured spectrum we calculate the first and second moments for different minimum photon energies, which are used to extract the heavy-quark parameters m{sub b} and [mu]{sub {pi}}2. In addition, measurements of the direct CP asymmetry and isospin asymmetry are presented.
The photon spectrum in B 2!X{sub s}[gamma] decay, where X{sub s} is any strange hadronic state, is studied using a data sample of 88.5 x 106 ee− 2![Upsilon](4S) 2!B{bar B} decays collected by the BABAR experiment at SLAC. The partial branching fraction, [Delta][Beta](B 2!X{sub s}[gamma]) = (3.67 ± 0.29(stat.) ± 0.34(sys.) ± 0.29(model)) x 10−4, the first moment E{sub {gamma}} = 2.288 ± 0.025 ± 0.017 ± 0.015 GeV and the second moment E{sub {gamma}}2 = 0.0328 ± 0.0040 ± 0.0023 ± 0.0036 GeV2 are measured for the photon energy range 1.9 GeV E{sub {gamma}}
Using 88.9 million B{bar B} events collected by the BABAR detector at the?(4S), they measure the branching fraction for the radiative penguin process B → X{sub s}? from the sum of 38 exclusive final states. The inclusive branching fraction above a minimum photon energy E{sub?}> 1.9 GeV is?(b → s?) = (3.27 ± 0.18(stat.){sub -0.40}{sup +0.55}(syst.){sub -0.09}{sup +0.04}(theory)) x 10−4. They also measure the isospin asymmetry between B− → X{sub s{bar u}}? and {bar B}° → X{sub sd}{gamma} to be?0 = -0.006 ± 0.058(stat.) ± 0.009(syst.) ± 0.024({bar B}°/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 m{sub b} and?{sub {pi}}2. The fitted parameters are consistent with those obtained from semileptonic B → X{sub c}l? decays, and are useful inputs for the extraction of.