标题： 使用企鹅算符：$b \to s γ$的一些-exclusive模式的分支比的格点计算 显示英文标题

标题： Probing with Penguins: A lattice calculation of the branching ratio for some of the exclusive modes of $b \to s γ$

摘要： 我们计算了在夸克禁闭的格点QCD中，用O(a)改善的费米子作用，在$24^3\times48$晶格上于$\beta=6.2$温度下，$b \to s\gamma$的非弹性衰变的主阶矩阵元。这个矩阵元被用于提取$B \to K^*\gamma$和$B_s \to \phi\gamma$的形式因子$T_1(q^2=0)$，采用关于这些衰变的形式因子的$q^2$依赖性的两种不同假设。 对于 $B \to K^*\gamma$， $T_1(q^2=0)$ 在两种情况下分别被确定为 $0.159^{+34}_{-33}\pm 0.067$ 或 $0.124^{+20}_{-18} \pm 0.022$。我们发现结果（在标准模型中）与 CLEO 实验的 $BR(B\to K^*\gamma) = (4.5 \pm 1.5 \pm 0.9) \times 10^{-5}$ 分支比一致。 显示英文摘要

摘要： We calculate the leading-order matrix element for exclusive decays of $b \to s\gamma$ in the quenched approximation of lattice QCD on a $24^3\times48$ lattice at $\beta=6.2$, using an O(a)-improved fermion action. The matrix element is used to extract the on-shell form factor $T_1(q^2=0)$ for $B \to K^*\gamma$ and $B_s \to \phi\gamma$, using two different assumptions about the $q^2$ dependence of the form factors for these decays. For $B \to K^*\gamma$, $T_1(q^2=0)$ is determined to be $0.159^{+34}_{-33}\pm 0.067$ or $0.124^{+20}_{-18} \pm 0.022$ in the two cases. We find the results to be consistent (in the Standard Model) with the CLEO experimental branching ratio of $BR(B\to K^*\gamma) = (4.5 \pm 1.5 \pm 0.9) \times 10^{-5}$.