Quasi-two-body decays B_(c)→D^(*)h→Dπh in perturbative QCD

In this work,we investigate the quasi-two-body decays B_(c)→D^(*)h→Dπhwithh=(K^(0),π^(0),η,η′)using the perturbative QCD(PQCD)approach.The description of final state interactions of the Dπpair is achieved through the two-meson distribution amplitudes(DAs),which are normalized to the time-like form factor.The PQCD predictions on the branching ratios of the quasi-two-body decays B_(c)→D^(*)h→Dπh show an obvious hierarchy:Br(B^(+)_(c)→D^(∗+)K^(0)→D^(0)π^(+)K^(0))=(5.22^(+0.86)_(-0.74))×10^(-6),Br(B^(+)_(c)→D^(∗+)π^(0)→D^(0)π^(+)π^(0))=(0.93±0.26)×10^(-7),Br(B^(+)_(c)→D^(∗+)η→D^(0)π^(+)η)=(2.83^(+0.59)_(-0.52))×10^(-8)and Br(B^(+)_(c)→D^(∗+)η′→D^(0)π^(+)η′)=(1.89+0.40-0.36)×10^(-8).From the invariant mass m Dπ-dependence of the decay spectrum for each channel,one can find that the branching fraction is concentrated in a narrow region around the D*pole mass.Thus,one can obtain the branching ratios for the corresponding two-body decays B_(c)→D^(*+)h under the narrow-width approximation.We find that the branching ratios of the decays B_(c)→D^(*+)h are consistent with the previous PQCD calculations within errors.These predictions will be tested in future experiments.

Insights into the nature of X(3872)through B meson decays

We study the Bc,u,d→X(3872)P decays in the perturbative QCD(PQCD)approach,involving the puzzling resonance X(3872),where P represents a light pseudoscalar meson(K orπ).Assuming X(3872)to be a 1++charmonium state,we obtain the following results.(a)The branching ratios of the Bc+→X(3872)π+and Bc+→X(3872)K+decays are consistent with the results predicted by the covariant light-front approach within errors;however,they are larger than those given by the generalized factorization approach.(b)The branching ratio of the B+→X(3872)K+decay is predicted as(3.8-1.0+1.1)×10-4,which is smaller than the previous PQCD calculation result but still slightly larger than the upper limits set by Belle and BaBar.Hence,we suggest that the B0,+→X(3872)K0,+decays should be precisely measured by the LHCb and Belle II experiments to help probe the inner structure of X(3872).(c)Compared with the Bu,d→X(3872)K decays,the Bu,d→X(3872)πdecays have significantly smaller branching ratios,which drop to values as low as 10-6.(d)The direct CP violations of these considered decays are small(10-3~10-2)because the penguin contributions are loop suppressed compared to the tree contributions.The mixing-induced CP violation of the B→X(3872)K0S decay is highly consistent with the current world average value sin 2β=(69.9±1.7)%.Experimentally testing the results for the branching ratios and CP violations,including the implicit SU(3)and isospin symmetries of these decays,helps probe the nature of X(3872).

Quasi-two-body B_((s))→K^(*)γ→Kπγ decays in the perturbative QCD approach

In this study,we investigate quasi-two-body B_((s))→K^(*)γ→Kπγ decays in the perturbative QCD approach.Two-meson distribution amplitudes are introduced to describe the final state interactions of the Kπpair,which involve time-like form factors and Gegenbauer polynomials.We calculate the CP averaged branching ratios of the B_((s))→K^(*)γ→Kπγ decays.Our results are in agreement with newly updated data measured by Belle Ⅱ.This suggests that it is more appropriate to analyze these quasi-two-body B decays in the three-body framework than the two-body framework.We also predict direct CP asymmetries for the considered decay modes and find that A_CP(B_(u,d)→K^(*)γ→Kπγ) is small and less than 1% in magnitude,whereas A_CP(B_(s)→K^(*)γ→Kπγ)is larger and can reach a few percent.Our predictions can be tested in future B meson experiments.