D-D¯ mixing and rare D decays in the littlest Higgs model with non-unitarity matrix

We study the D-D¯ mixing and rare D decays in the littlest Higgs model. As the new weak singlet quark with the electric charge of 2/3 is introduced to cancel the quadratic divergence induced by the top quark, the standard unitary 3×3 Cabibbo-Kobayashi-Maskawa matrix is extended to a non-unitary 4×3 matrix in the quark charged currents and Z-mediated flavor changing neutral currents are generated at tree level. In this model, we show that the D-D¯ mixing parameter can be as large as the current experimental value and the decay branching ratio (BR) of D→Xuγ is small but its direct CP asymmetry could be O(10%). In addition, we find that the BRs of D→Xuℓ+ℓ−, D→Xuνν¯ and D→μ+μ− could be enhanced to be O(10−9), O(10−8) and O(10−9), respectively.