Measurement of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi><mml:mo>→</mml:mo><mml:msub><mml:mi>X</mml:mi><mml:mi>s</mml:mi></mml:msub><mml:mi>γ</mml:mi></mml:math>branching fraction and photon energy spectrum using the recoil method

We present a measurement of the branching fraction and photon-energy spectrum for the decay $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ using data from the BABAR experiment. The data sample corresponds to an integrated luminosity of $210\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, from which approximately 680 000 $B\overline{B}$ 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 $\mathcal{B}(B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma})=(3.66\ifmmode\pm\else\textpm\fi{}{0.85}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.60}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ for photon energies ${E}_{\ensuremath{\gamma}}$ 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 ${m}_{\mathrm{b}}$ and ${\ensuremath{\mu}}_{\ensuremath{\pi}}^{2}$. In addition, measurements of the direct $CP$ asymmetry and isospin asymmetry are presented.

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