Paper
Analysis of the Photon Spectrum in Inclusive $B\to X_s\,γ$ Decays
Authors
Abstract
Using a combination of the operator product and heavy quark expansions, we resum the leading nonperturbative contributions to the inclusive photon spectrum in decays. The shape of the spectrum is determined by a universal structure function, which describes the distribution of the light-cone momentum of the -quark inside the -meson. The moments of this function are proportional to forward matrix elements of higher-dimension operators. As a by-product, we obtain the bound for one of the parameters of the heavy quark effective theory. The integral over the structure function is related to the shape function that governs the fall-off of the lepton spectrum close to the endpoint in decays. A measurement of the photon spectrum in rare -decays can therefore help to obtain a model-independent determination of .