标题： $|V_{cb}|$来自重夸克跃迁的OPE求和规则 显示英文标题

标题： $|V_{cb}|$ from OPE Sum Rules for Heavy Flavor Transitions

摘要： 我们推导出在零动量转移时，$B\ra D^*$转换的轴矢量形式因子的模型无关上限，$F_{B\ra D^*}$。 该形式因子明显小于1。 $F_{B\ra D^*}$与1的偏离比之前预期的大。 使用我们的估计值，我们从测量到的$B\ra D^* l\nu$的独占率中提取$|V_{cb}|$，并将其外推到零动量转移点。 $|V_{cb}|$的中心“独占”值与从包括性半轻子宽度$\Gamma (B\ra X_c l\nu)$得到的值一致。 我们认为，如果考虑来自重夸克展开的夸克质量差$m_b - m_c$的约束，则从总不变宽度中确定$|V_{cb}|$的理论不确定性会显著降低。 显示英文摘要

摘要： We derive a model-independent upper bound for the axial-vector form factor of the $B\ra D^*$ transition at zero recoil, $F_{B\ra D^*}$. The form factor turns out to be noticeably less than unity. The deviation of $F_{B\ra D^*}$ from unity is larger than previously anticipated. Using our estimate we extract $|V_{cb}|$ from the measured exclusive rate of $B\ra D^* l\nu$ extrapolated to the point of zero recoil. The central `` exclusive" value of $|V_{cb}|$ is in agreement with the value obtained from the inclusive semileptonic width $\Gamma (B\ra X_c l\nu)$. We argue that the theoretical uncertainty in determining $|V_{cb}|$ from the total inclusive width is significantly reduced if a constraint on the quark mass difference $m_b - m_c$ stemming from the heavy quark expansion is taken into account.