Ds→K,K*, φ form factors in the covariant light-front approach and exclusive Ds decays

In the covariant light-front quark model, we investigate the form factors of D-s -> K, K*, phi transitions and compare our results with the experimental data and the previous theoretical studies. The semileptonic D-s decays are studied: our result for the branching ratio of D-s phi l(+) nu is consistent with the data; while the other predictions, such as BR(D-s(+) -> (K) over bar (0) l(+) nu), the branching ratio and the polarization of D-s -> (K) over bar (0) l(+) nu, will be tested at the future experiments. Utilizing the results for form factors, we then calculate the two-body nonleptonic Ds decays and find: up to the leading power accuracy, theoretical predictions on branching ratios of nonleptonic Ds decays are typically smaller than the experimental data by a factor of 1.5-2.0. Large contributions from weak annihilation diagrams, together with the s, t-channel final state interactions, are expected to resolve this problem. The D-s -> K+ K*(0) decay, which can be easily measured in the K+ K- pi(-) final state, can directly shed light on internal information of the doubly Cabibbo-suppressed decay amplitudes.