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

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 ${}^3{P}_1$ and ${}^1{P}_1$ 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 $B\to K^{\ast }\gamma$, $B\to K_1(1270)\gamma$, $K_1(1400)\gamma$ 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 $B_s\to \varphi \gamma$ 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$f’_2(1525)\gamma$arepredictedtobeoforder$10^{-5}$anditwillbeinterestingtosearchforthesemodes\mathrm{.}Rateson$B_s\to f_1(1285)\gamma$,$h_1(1380)\gamma$,$h_1(1170)\gamma$,$f_2(1270)\gamma$ decays are also predicted.