Svjetlana Fajfer (Ljubljana):

Search for new physics in rare D decays

Abstract:

In many extensions of the standard model an additional up-like heavy quark appears. Its appearance induces flavour changing neutral current transition in the up-quark region at the tree level. We investigate possible effects of these models in the c → ul⁺l^- transitions. First we determine impact of new physics on the relevant Wilson coefficients and then we reevaluate the standard model long-distance contributions. We calculate differential branching ratio for the D⁺ → π⁺ l⁺ l^- and D⁰ → ρ⁰ l⁺ l^- decays. Among all D decay modes these two are the simplest ones for the experimental studies. We also determine the forward - backward asymmetry for the D⁰ → ρ⁰ l⁺ l^- decay and we comment on the effects of the Littlest Higgs model in both decay modes.