B to V, A, T Tensor Form Factors in the Covariant Light-Front Approach: Implications on Radiative B Decays

TL;DR

This paper reanalyzes B meson tensor form factors using a covariant light-front model, improving treatment of meson mixing, and calculates radiative decay rates that align well with experimental data, providing predictions for various B_s decay modes.

Contribution

It introduces an improved covariant light-front approach for B to tensor meson form factors and applies it to predict radiative decay rates, including updated mixing angles and new decay mode predictions.

Findings

Calculated B to V, A, T form factors agree with experimental data.

Determined the K1(1270)-K1(1400) mixing angle to be about 51°.

Predicted branching fractions for several B_s radiative decays.

Abstract

We reanalyze the $B\to M$ tensor form factors in a covariant light-front quark model, where $M$ represents a vector meson $V$, an axial-vector meson $A$, or a tensor meson $T$. The treatment of masses and mixing angles in the $K_{1A,1B}$ systems is improved, where $K_{1A}$ and $K_{1B}$ are the $^3P_1$ and $^1P_1$ states of the axial-vector meson $K_1$, respectively. Rates of $B\to M\gamma$ decays are then calculated using the QCD factorization approach. The updated $B\to K^*\gamma$, $B\to K_1(1270)\gamma$, $K_1(1400)\gamma$ and $K_2\gamma$ rates agree with the data. The $K_1(1270)$--$K_1(1400)$ mixing angle is found to be about $51^\circ$. The sign of the mixing angle is fixed by the observed relative strength of $B\to K_1(1270)\gamma$ and $K_1(1400)\gamma$. The formalism is then applied to $B_s\to M$ tensor form factors. We find that the calculated $B_s\to \phi\gamma$ rate is consistent with experiment, though in the lower end of the data. The branching fractions of $B_s\to f_1(1420)\gamma$ and $f'_2(1525)\gamma$ are predicted to be of order $10^{-5}$ and it will be interesting to search for these modes. Rates on $B_s\to f_1(1285)\gamma$, $h_1(1380)\gamma$, $h_1(1170)\gamma$, $f_2(1270)\gamma$ decays are also predicted.