paper

from OPE Sum Rules for Heavy Flavor Transitions

arXiv:hep-ph/9405207 · doi:10.1103/PhysRevD.51.2217 10.1103/PhysRevD.52.3149

Abstract

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 from the measured exclusive rate of $B\ra D^* lν$ extrapolated to the point of zero recoil. The central `` exclusive" value of is in agreement with the value obtained from the inclusive semileptonic width $Γ(B\ra X_c lν)$. We argue that the theoretical uncertainty in determining from the total inclusive width is significantly reduced if a constraint on the quark mass difference stemming from the heavy quark expansion is taken into account.

14 pages + uuencoded ps file with 1 figure, Latex, TPI-MINN-94/13-T, NSF-ITP-94-39

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