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 $^3P_1$ and $^1P_1$ states of the axial-vector meson $K_1$, respectively. Rates of $B\to Mγ$ decays are then calculated using the QCD factorization approach. The updated $B\to K^*γ$, $B\to K_1(1270)γ$, $K_1(1400)γ$ and $K_2γ$ 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 $B\to K_1(1270)γ$ and $K_1(1400)γ$. The formalism is then applied to $B_s\to M$ tensor form factors. We find that the calculated $B_s\to ϕγ$ rate is consistent with experiment, though in the lower end of the data. The branching fractions of $B_s\to f_1(1420)γ$ and $f'_2(1525)γ$ are predicted to be of order $10^{-5}$ and it will be interesting to search for these modes. Rates on $B_s\to f_1(1285)γ$, $h_1(1380)γ$, $h_1(1170)γ$, $f_2(1270)γ$ decays are also predicted.

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