Covariant Light-Front Approach for B to K* gamma, K1 gamma, K*2 gamma Decays
Abstract
Exclusive radiative B decays, B to K* gamma, K1(1270) gamma, K1(1400) gamma and K*2(1430) gamma, are studied in the framework of a covariant light-front quark model. The tensor form factor T1(q2) at q2=0, which is relevant to the decay B to K* gamma, is found to be 0.24, substantially smaller than what expected from the conventional light-front model or light-cone sum rules. Taking into account the sizable next-to-leading order (NLO) corrections, the calculated branching ratio of B to K* gamma agrees with experiment, while most of the existing models predict too large B to K* gamma compared to the data. The relative strength of B to K1(1270) gamma and B to K1(1400) gamma rates is very sensitive to the sign of the K1(1270)-K1(1400) mixing angle. Contrary to the other models in which K1(1270) gamma and K1(1400) gamma rates are predicted to be comparable, it is found that one of them is strongly suppressed owing to a large cancellation between two different form factor terms. The calculated branching ratio of B to K*2 gamma is in a good agreement with experiment and this may imply the smallness of NLO corrections to this radiative decay mode.
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