$B \to D^{(*)}$ Form Factors from QCD Light-Cone Sum Rules

TL;DR

This paper derives new QCD light-cone sum rules for $B o D^{(*)}$ form factors using $B$-meson distribution amplitudes, providing theoretical predictions that are compared with experimental data for validation.

Contribution

It introduces a novel approach to calculating $B o D^{(*)}$ form factors using light-cone sum rules with $B$-meson DAs, incorporating finite charm-quark mass effects.

Findings

Calculated $B o D^{(*)}$ form factors at small momentum transfer.

In the heavy-quark limit, sum rules reduce to the Isgur-Wise function.

Predictions agree with experimental decay rate analyses.

Abstract

We derive new QCD sum rules for $B\to D$ and $B\to D^*$ form factors. The underlying correlation functions are expanded near the light-cone in terms of $B$-meson distribution amplitudes defined in HQET, whereas the $c$-quark mass is kept finite. The leading-order contributions of two- and three-particle distribution amplitudes are taken into account. From the resulting light-cone sum rules we calculate all $B\to \Dst $ form factors in the region of small momentum transfer (maximal recoil). In the infinite heavy-quark mass limit the sum rules reduce to a single expression for the Isgur-Wise function. We compare our predictions with the form factors extracted from experimental $B\to \Dst l \nu_l$ decay rates fitted to dispersive parameterizations.