Pure annihilation type Bc→M2M3 decays in the perturbative QCD approach

In the standard model the two-body charmless hadronic Bc meson decays can occur via annihilation diagrams only. In this work, we studied the Bc→PP, PV/VP, VV decays by employing the perturbative QCD (pQCD) factorization approach. From our calculations, we find that (a) the pQCD predictions for the branching ratios of the considered Bc decays are in the range of 10-6 to 10-8; (b) for Bc→PV/VP, VV decays, the branching ratios of ΔS=0 decays are much larger than those of ΔS=1 because the different Cabibbo-Kobayashi-Maskawa (CKM) factors are involved; (c) analogous to B→Kη(') decays, we find Br(Bc→K+η')∼10xBr(Bc→K+η), which can be understood by the destructive and constructive interference between the ηq and ηs contribution to the Bc→K+η and Bc→K+η' decay; (d) the longitudinal polarization fractions of Bc→VV decays are in the range of 86%-95% and play the dominant role; and (e) there is no CP-violating asymmetries for the considered Bc decays because only one type tree operator is involved.