D~0-~0 mixing parameter y in the factorization-assisted topological-amplitude approach

We calculate the D~0-~0 mixing parameter y in the factorization-assisted topological-amplitude(FAT)approach, considering contributions from D~0→PP, PV, and VV modes, where P(V) stands for a pseudoscalar(vector) meson. The D~0→PP and PV decay amplitudes are extracted in the FAT approach, and the D~0→VV decay amplitudes with final states in the longitudinal polarization are estimated via the parameter set for D~0→PV. It is found that the VV contribution to y, being of order of 10-4, is negligible, and that the PP and PV contributions amount only up to y_(PP+PV) =(0.21±0.07)%, a prediction more precise than those previously obtained in the literature,and much lower than the experimental data y_(exp) =(0.61 ±0.08)%. We conclude that D~0 meson decays into other two-body and multi-particle final states are relevant to the evaluation of y, so it is difficult to understand it fully in an exclusive approach.