D0-(D)over-bar0 mixing parameter y in the factorization-assisted topological-amplitude approach

We calculate the D-0-(D) over bar (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.