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.

Revisiting radiative leptonic B decay

In this paper,we summarize the existing methods of solving the evolution equation of the leading-twist B-meson LCDA.Then,in the Mellin space,we derive a factorization formula with next-to-leading-logarithmic(NLL)resummation for the form factors FA,V in the B→γℓνdecay at leading power inΛ/mb.Furthermore,we investigate the power suppressed local contributions,factorizable non-local contributions(which are suppressed by 1/Eγand 1/mb),and soft contributions to the form factors.In the numerical analysis,which employs the two-loop-level hard function and the jet function,we find that both the resummation effect and the power corrections can sizably decrease the form factors.Finally,the integrated branching ratios are also calculated for comparison with future experimental data.

Λ_(b)→Λ_(c) form factors from QCD light-cone sum rules

In this study,we calculate the transition form factors of Λ_(b) decaying into Λ_(c) within the framework of light-cone sum rules with the distribution amplitudes(DAs)of the Λ_(b)-baryon.In the hadronic representation of the correlation function,we isolate both the Λ_(c) and Λ_(c)^(∗) states so that the Λ_(b)→Λ_(c) form factors can be obtained without ambiguity.We investigate the P-type and A-type currents to interpolate light baryons for comparison because the interpolation current for the baryon state is not unique.We also employ three parametrization models for the DAs of Λ_(b) in the numerical calculation.We present the numerical predictions for the Λ_(b)→Λ_(c) form factors and branching fractions,averaged forward-backward asymmetry,averaged final hadron polarization,and averaged lepton polarization of the Λ_(b)→Λ_(c)ℓμ decays,as well as the ratio of the branching ratios RΛ_(c).The predicted RΛ_(c) is consistent with LHCb data.

Weak decays of doubly heavy baryons:"decay constants"

Inspired by the recent observation of the ∑c^＋c^＋ by the LHCb Collaboration, we explore the ＂decay constants＂ of doubly heavy baryons in the framework of QCD sum rules. With the ∑cc,∑bb, and Ωcc,Ωbc,Ωbb baryons interpolated by three-quark operators, we calculate the correlation functions using the operator product expansion and include the contributions from operators up to dimension six. On the hadron side, we consider both contributions from the lowest-lying states with J^P 1/2^＋ and from negative parity baryons with JP=1/2^-. We find that the results are stable and the contaminations from negative parity baryons are not severe. These results are ingredients for the QCD study of weak decays and other properties of doubly-heavy baryons.