D{sub s}{yields}K, K, {phi} form factors in the Covariant Light-Front Approach and Exclusive D{sub s} Decays

In the covariant light-front quark model, we investigate the form factors of D{sub s}{yields}K, K*, {phi} transitions and compare our results with the experimental data and the previous theoretical studies. The semileptonic D{sub s} decays are studied: our result for the branching ratio of D{sub s}{yields}{phi}l{sup +}{nu} is consistent with the data; while the other predictions, such as BR(D{sub s}{sup +}{yields}K{sup 0}l{sup +}{nu}), the branching ratio and the polarization of D{sub s}{yields}K*{sup 0}l{sup +}{nu}, will be tested at the future experiments. Utilizing the results for form factors, we then calculate the two-body nonleptonic D{sub s} decays and find: up to the leading power accuracy, theoretical predictions on branching ratios of nonleptonic D{sub s} 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{sub s}{yields}K{sup +}K*{sup 0} decay, which can be easily measured in the K{sup +}K{sup +}{pi}{sup -} final state, can directly shed light on internal information of the doubly Cabibbo-suppressed decay amplitudes.