Branching Fraction and Photon Energy Spectrum forb→sγ

Abstract

We have measured the branching fraction and photon energy spectrum for the radiative penguin process $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$. We find $B(b\ensuremath{\rightarrow}s\ensuremath{\gamma})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(3.21\ifmmode\pm\else\textpm\fi{}0.43\ifmmode\pm\else\textpm\fi{}{0.27}_{\ensuremath{-}0.10}^{+0.18})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, where the errors are statistical, systematic, and from theory corrections. We obtain first and second moments of the photon energy spectrum above 2.0 GeV, $〈{E}_{\ensuremath{\gamma}}〉\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.346\ifmmode\pm\else\textpm\fi{}0.032\ifmmode\pm\else\textpm\fi{}0.011\mathrm{GeV}$, and $〈{E}_{\ensuremath{\gamma}}^{2}〉\ensuremath{-}〈{E}_{\ensuremath{\gamma}}{〉}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.0226\ifmmode\pm\else\textpm\fi{}0.0066\ifmmode\pm\else\textpm\fi{}0.0020{\mathrm{GeV}}^{2}$, where the errors are statistical and systematic. From the first moment, we obtain (in the modified minimal subtraction renormalization scheme, to order ${1/M}_{B}^{3}$ and ${\ensuremath{\beta}}_{0}{\ensuremath{\alpha}}_{s}^{2}$) the heavy quark effective theory parameter $\overline{\ensuremath{\Lambda}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.35\ifmmode\pm\else\textpm\fi{}0.08\ifmmode\pm\else\textpm\fi{}0.10\mathrm{GeV}$.