Looking for new physics via semi-leptonic and leptonic rare decays of D and D_s

Abstract：

It is well recognized that looking for new physics at lower energy colliders is a path which is complementary to high energy machines such as the LHC. Using the large volume of data collected by BESⅢ, we may have a unique opportunity to tackle this. In this paper we calculate the branching ratios of the semi-leptonic processes D _s ⁺→ K ⁺e ^-e ⁺and D _s ⁺→K ⁺e ^-μ ⁺, and the leptonic processes D ⁰→ e ^-e ⁺and D ⁰→ e ^-μ ⁺, in the frameworks of the U(1)' model, 2HDM and unparticle model. It is found that both the U(1)' model and 2HDM may influence the semi-leptonic decay rates, but only the U(1)' model offers substantial contributions to the pure leptonic decays, and the resultant branching ratio of D ⁰→ e ^-μ ⁺can be as large as 10 ^-7~10 ^-8. This might be observed at the future super τ-charm factory.