Effects from hadronic structure of photon on B→φγ and B_(s)→(ρ^(0),ω)γ decays

Using the perturbative QCD approach,we studied the effects of the hadronic structure of photons on the pure annihilation rediative decays B→φγ and B_(s)→(ρ^(0),ω)γ.These decays have small branching fractions due to the power suppression by Λ/mB,which makes them very sensitive to next-leading power corrections.The quark components and the related two-particle distribution amplitudes of a final state photon are introduced.The branching fractions can be enhanced remarkably by factorizable and nonfactorizable emission diagrams.The branching fraction of B→φγ increases by approximately 40 times,and those of B_(s)→ρ^(0)γ and B_(s)→ωγ are on the order of O(10-10).We also note that the ratio of branching fractions of B_(s)→ρ^(0)γ and B_(s)→ωγ is very sensitive to the effects of the hadronic structure of photons.All these results can be tested in future.

Pure annihilation type D→PP(V) decays in the perturbative QCD approach

The annihilation type diagrams are difficult to calculate in any kind of model or method. Encouraged by the successful calculation of pure annihilation type B decays in the perturbative QCD factorization approach, we calculate the pure annihilation type D→ PP（V） decays in the perturbative QCD approach based on the kw factorization. Although the expansion parameter 1lind is not very small, our leading order numerical results agree with the existing experimental data for most channels. We expect more accurate observation from experiments, which can help us learn about the dynamics of D meson weak decays.

Investigation on effects of new physics in c→(s,d)l+νltransitions

Anomalies in decays induced by b→ct Ve(l=e,μ,T)transitions may imply lepton flavor universality violations,which raises questions on such phenomena in the D decays induced by c→(s,d)t+ve transitions.Current measurements of the pure leptonic and semi-leptonic D decays agree with the standard model(SM)predictions,and such agreements can be used to constrain the new physics(NP)contributions.In this work,we extend SM by as-suming general efective Hamiltonians describing the c→(s,d)t+Ve transitions including the full set of the four-fermion operators.With the latest experimental data,we perform a least χ^(2) fit of the Wilson cofficient corresponding to each operator.The results indicate that the Wilson coefficients of tensor and scalar operators in the muon sector are in the order of 0(10^(-2))while others are in the order of 0(10^(-3)).The lepton flavor universality could be violated by interactions with the scalar operators.We also determine that the pure leptonic decays are significantly sensitive to scalar operators.The efects of NP on the semi-leptonic decays with electron final state are negligible;however,for the decays with the muon final state,the effects of scalar and tensor operators will appear in the forward-back-ward asymmetries and the muon helicity asymmetries of D→Pμ^(+)Vpμdecays.The future measurements of these de-cays in the BESIII and Belle II experiments will facilitate the evaluation of NP effects.

Constraining the UT angle γ by CP violation parameters in B^0→π^＋π^-

We calculate the tree and penguin amplitudes in the B^0→π^＋^-ecay channel employing the perturbative QCD factorization approach. Using the amplitudes as input with the theoretical uncertainties sufficiently considered, we constrain the UT angle γ to 53°γ 70°, from the measurements of the CP violation parameters C_（π^＋^- and S_（π^＋^-in B^0→π^＋^- The U-spin breaking effect between B^0→π^＋^-nd B^0 s →K^＋K^-is estimated to be around 30%.