Charmless $B_{c} \to VV$ decays in the QCD factorization approach

TL;DR

This paper analyzes charmless Bc to VV decays using QCD factorization, comparing two schemes for end-point divergence regulation, and predicts observable branching ratios and polarization dominance.

Contribution

It introduces and compares two schemes for regulating end-point divergences in QCD factorization for Bc to VV decays, providing numerical predictions for branching ratios and polarization fractions.

Findings

Branching ratios around 10^{-7} for certain decay modes.

Decay modes are predominantly longitudinally polarized.

Scheme II yields larger annihilation amplitudes than scheme I.

Abstract

In this paper, we studied the charmless $B_{c}\to VV$ ($V$ denotes the light ground $\rm SU(3)$ vector meson) decays within the framework of QCD factorization. In the evaluation, two different schemes for regulating the end-point divergence are adopted. One (scheme I) is to use parameterization model, which is usually employed in the QCD factorization approach; the other (scheme II) is based on the infrared finite gluon propagator of Cornwall prescription. It is found that, in the annihilation amplitudes, the end-point divergence appears only in the power-suppressed corrections related to the twist-3 distribution amplitudes of $V$-meson. The strength of annihilation amplitudes evaluated in scheme II is generally larger than the one in scheme I. Numerically, in the decay modes considered in this paper, the CKM-favored $B_{c} \to \rho^{-}\omega, K^{*-}K^{*0} $ decays have the relatively large branching fractions, $\sim {\cal{O}}(10^{-7})$, and hence are likely to be the first observed by the future experiments. In addition, all of the decay modes are dominated by the longitudinal polarization state; numerically, $f_{L}(B_{c} \to VV) \gtrsim 99\%$.