Moments of the photon energy spectrum from $B\to X_s \gamma$ decays measured by Belle

Abstract

We report preliminary measurements of the first (mean) and second moment (variance) of the inclusive photon energy spectrum in $B\to X_s\gamma$ decays, for threshold values of the photon energy in the range 1.8--2.3 GeV as measured in the rest frame of the $B$-meson. These results are obtained from the Belle measurement of the spectrum, which used a data set consisting of 152 million $B\bar{B}$ pairs collected by the Belle detector at the KEKB asymmetric-energy electron-positron collider operated on the $\Upsilon(4S)$ resonance.