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

We study the D-D-bar 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 3x3 Cabibbo-Kobayashi-Maskawa matrix is extended to a non-unitary 4x3 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-bar 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-bar and D→μ+μ- could be enhanced to be O(10-9), O(10-8) and O(10-9), respectively