$B\to D_1(2420)$ and $B\to D_1'(2430)$ form factors from QCD light-cone sum rules

TL;DR

This paper calculates the form factors for semileptonic B decays to D1(2420) and D1'(2430) mesons using QCD light-cone sum rules with a novel approach to distinguish contributions, providing numerical results and decay constants.

Contribution

First calculation of B to D1(2420) and D1'(2430) form factors using LCSRs with a new method to separate meson contributions and fixing parameters with sum rules and experimental data.

Findings

Numerical form factors for B to D1 and D1' decays.

Predicted decay constants for D1 and D1' mesons.

Estimated lepton-flavour universality ratios R(D1) and R(D1').

Abstract

We perform the first calculation of form factors in the semileptonic decays $B\!\to\! D_1(2420)\ell\nu_\ell$ and $B \to D_1^\prime (2430)\ell \nu_\ell$ using QCD light-cone sum rules (LCSRs) with $B$-meson distribution amplitudes. In this calculation the $c$-quark mass is finite. Analytical expressions for two-particle contributions up to twist four are obtained. To disentangle the $D_1$ and $D_1^\prime$ contributions in the LCSRs, we suggest a novel approach that introduces a combination of two interpolating currents for these charmed mesons. To fix all the parameters in the LCSRs, we use the two-point QCD sum rules for the decay constants of $D_1$ and $D_1^\prime$ mesons augmented by a single experimental input, that is the $B \to D_1(2420)\ell\nu_\ell$ decay width. We provide numerical results for all $B\to D_1$ and $B\to D_1^\prime$ form factors. As a byproduct, we also obtain the $D_1$- and $D_1'$-meson decay constants and predict the lepton-flavour universality ratios $R(D_1)$ and $R(D_1')$.