We use 772$times 10^6$ $B bar{B}$ meson pairs collected at the $Upsilon(4S)$ resonance with the Belle detector to measure the branching fraction for $bar{B} rightarrow X_s gamma$. Our measurement uses a sum-of-exclusives approach in which 38 of the h
adronic final states with strangeness equal to $+1$, denoted by $X_s$, are reconstructed. The inclusive branching fraction for $M_{X_s}<$ 2.8 GeV/$c^2$, which corresponds to a minimum photon energy of 1.9 GeV, is measured to be ${cal B}(bar{B} rightarrow X_s gamma)=(3.51pm0.17pm0.33)times10^{-4}$, where the first uncertainty is statistical and the second is systematic.
We report the first measurement of the lepton forward-backward asymmetry ${cal A}_{rm FB}$ as a function of the squared four-momentum of the dilepton system, $q^2$, for the electroweak penguin process $B rightarrow X_s ell^+ ell^-$ with a sum of excl
usive final states, where $ell$ is an electron or a muon and $X_s$ is a hadronic recoil system with an $s$ quark. The results are based on a data sample containing $772times10^6$ $Bbar{B}$ pairs recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. ${cal A}_{rm FB}$ for the inclusive $B rightarrow X_s ell^+ ell^-$ is extrapolated from the sum of 10 exclusive $X_s$ states whose invariant mass is less than 2 GeV/$c^2$. For $q^2 > 10.2$ GeV$^2$/$c^2$, ${cal A}_{rm FB} < 0$ is excluded at the 2.3$sigma$ level, where $sigma$ is the standard deviation. For $q^2 < 4.3$ GeV$^2$/$c^2$, the result is within 1.8$sigma$ of the Standard Model theoretical expectation.
