Transition form factors of B decays into p-wave axial-vector mesons in the perturbative QCD approach

TL;DR

This paper calculates B meson decay form factors into p-wave axial-vector mesons using perturbative QCD, providing predictions for decay rates and a model-independent method to analyze meson mixing effects.

Contribution

It offers the first perturbative QCD calculations of B to axial-vector meson form factors across the entire kinematic range and introduces a model-independent approach to determine mixing angles.

Findings

Form factors have the same sign for both axial-vector types.

Most semileptonic decay branching fractions are around 10^{-4}.

Proposes a new method to reduce mixing angle ambiguities.

Abstract

The $B_{u,d,s}\to V,A$ form factors are studied in perturbative QCD approach ($V,A$ denote a vector meson and two kinds of p-wave axial-vector mesons: $^3P_1$ and $^1P_1$ states, respectively.). The form factors are directly studied in the large recoiling region and extrapolated to the whole kinematic region within the dipole parametrization. Adopting decay constants with different signs for the two kinds of axial-vectors, we find that the two kinds of $B\to A$ form factors have the same sign. The two strange mesons $K_{1A}$ and $K_{1B}$ mix with each other via the SU(3) symmetry breaking effect. In order to reduce the ambiguities in the mixing angle between $K_{1A}$ and $K_{1B}$, we propose a model-independent way that utilizes the B decay data. Most of the branching fractions of the semilteptonic $B\to Al\bar \nu_l$ decays are of the order $10^{-4}$, which still need experimental tests in the on-going and forthcoming experiments.