Analysis of B → a_1(1260)(b_1(1235))K decays in the perturbative QCD approach

Within the framework of the perturbative quantum chromodynamics(PQCD) approach, we study the charmless two-body decays B → a_1(1260)K*, b_1(1235)K*. Using the decay constants and the light-cone distribution amplitudes for these mesons derived from the QCD sum rule method, we find the following results.(a) Our predictions for the branching ratios are consistent with the QCD factorization(QCDF) results within errors, but much larger than the naive factorization approach calculation values.(b) We predict that the anomalous polarizations occurring in the decays B→φK*, ρK*also happen in B→a_1 K*decays, while they do not happen in B→b_1 K*decays. Here the contributions from the annihilation diagrams play an important role in explaining the larger transverse polarizations in the B→a_1 K*decays, while they are not sensitive to the polarizations for the B→b_1 K*decays.(c) Our predictions for the direct C P-asymmetries agree well with the QCDF results within errors. The decaysˉB~0→b_1_+K*-, B-→b_1~0K*-have larger direct C P-asymmetries, which could be measured by the present LHCb experiment and the forthcoming Super-B experiment.     

Pure annihilation type decays B0→Ds- （K2*）+ and Bs →a2 in the perturbative QCD approach

We calculate the branching ratios of pure annihilation type decays B 0 →D_s^- （K₂^*）⁺ and Bs → a₂ using the perturbative QCD approach based on k T factorization. The branching ratios are predicted to be （60.6 +17.3+4.3+3.2 16.5 10.4 2.1 ）× 10^-6 for B⁰ →D_s^- （K₂^*）⁺ , （1.1 +0.4+0.1+0.1-0.4-0.2-0.1 ）×10-6 for Bs → ⁰a₂⁰ and （2.3 +0.8+0.2+0.1-0.8-0.4-0.1 ）×10-6 for Bs→D^-a₂⁺ . They are large enough to be measured in the ongoing experiment. Due to the shortage of contributions from penguin operators, there are no direct CP asymmetries for these decays in the Standard Model. We also derive simple relations among these decay channels to reduce theoretical uncertainties for the experiments, to test the accuracy of theory, and to search for a signal of new physics.     

QCD Axial Anomaly Enhances the ηη' Decay of the Hybrid Candidate η1（1855）

We study the hybrid mesons with the exotic quantum number I^GJ^PG=0⁺1^-+ and investigate their decays into the ηη’,a₁（1260）π,f₁（1285）η,f₁（1420）η,K^*（892）■,K₁（1270）■,and K₁（1400）■channels.It is found that the QCD axial anomaly enhances the decay width of the ηη’ channel although this mode is strongly suppressed by the small p-wave phase space.Our results support the interpretation of the η     

Branching ratio and CP asymmetry of Bs→K0(1430)η(') decays in the PQCD approach

In the two-quark model supposition for K0*(1430), which can be viewed as either the first excited state (ScenarioⅠ) or the lowest lying state (Scenario Ⅱ), the branching ratios and the direct CP-violating asymmetries for decays s0 → K0*0(1430)η (’) are studied by employing the perturbative QCD factorization approach. We find the following results: (a) The CP averaged branching ratios ofs0 → K0*0 (1430)η ands0→ K0*0(1430)η’ are small and both in the order of 10-7 . If one views K0* (1430) as the lowest lying state, B(s0→K0*0(1430)η) ≈ 3.9×10-7 and B(s0→K0*0(1430)η’) ≈ 7.8×10-7.(b) While the direct CP-violating asymmetries of these two decays are not small: if we still take the parameters of K0* (1430) in scenario , ACPdir(s0→K0*0(1430)η) ≈ 56.2% and ACPdir(s0→ K0*0(1430)η’) ≈ 42.4%. (c) The annihilation contributions will play an important role in accounting for future data, because both the branching ratios and the direct CP asymmetries of these two decays are sensitive to the annihilation type contributions.     

B→K0^＊（1430）K Decays in Perturbative QCD Approach

In this article, we calculate the branching ratios of B→K0^＊ （1430）K decays by employing the pertur-bative QCD （pQCD） approach at leading order. We perform the evaluations in the two scenarios for the scalar meson spectrum. We find that （i） The leading order pQCD predictions for the branching ratio Br（B^＋→K^＋K0^＊（1430）^0）are in good agreement with the experimental upper limit in both scenarios, while the pQCD predictions for other considered B→K0^＊（1430）K decay modes are also presented and will be tested by the LHC experiments; （ii） The annihilation contributions play an important role in these considered decays, for B^0→K0^＊（1430）^±K^± decays,for example,which are found to be （1-4）×10^-6.     

B→（J/ψ,η_c）K decays in the perturbative QCD approach

In this paper,we calculated the B →（J/ψ,ηc） K decays in the perturbative QCD（pQCD） factorization approach with the inclusion of the partial next-to-leading order（NLO） contributions. With the inclusion of the significant enhancement from the NLO vertex corrections,the NLO pQCD predictions for the branching ratios agree with the data within 2σ errors：Br（B0 → J/ψK0） = 5.2-＋32..58×10-4,Br（B＋ → J/ψK＋） = 5.6-＋32..79×10-4,Br（B0 →ηcK0） = 5.5-＋22..30 × 10-4,Br（B＋ →ηcK＋） = 5.9-＋22..51 × 10-4.     

B→f0（980）（π,η^（＇）） decays in the PQCD approach

Based on the assumption of a two-quark structure of the scalar meson f0（980） ,we calculate the branching ratios and CP-violating asymmetries for the four B → f0（980） π and B → f0（980） η^（＇） decays by employing the perturbative QCD（pQCD） factorization approach. The leading order pQCD predictions for branching ratios are,Br（B^-→ f0（980） π^-） ～ 2.5×10^-6,Br（Bˉ^0 → f0（980） π^0） ～ 2.6×10^-7,Br（Bˉ^0 → f0（980） η） ～ 2.5×10^-7 and Br（Bˉ^0 → f0（980） η ） ～ 6.7×10^-7,which are consistent with both the QCD factorization predictions and the experimental upper limits.     

B→K0^＊（1430）η（＇） decays in the pQCD approach

Based on the assumption of two-quark structure of the scalar meson K0^＊（1430）, we calculate the CP-averaged branching ratios for B→K0^＊（1430）η（＇） decays in the framework of the perturbative QCD （pQCD） approach here. We perform the evaluations in two scenarios for the scalar meson spectrum. We find that： （a） the pQCD predictions for Br（B→K0^＊（1430）η（＇）） which are about 10^-5 10^-6, basically agree with the data within large theoretical uncertainty; （b） the agreement between the pQCD predictions and the data in Scenario Ⅰ is better than that in Scenario Ⅱ, which can be tested by the forthcoming LHC experiments; （c） the annihilation contributions play an important role for these considered decays.     

B → ρ（ω, φ）η（＇） Decays and NLO Contributions in pQCD Approach

By employing the perturbative QCD （pQCD） factorization approach, we calculate some important next- to-leading-order （NLO） contributions to the two-body charmless hadronic decays B^＋ →ρ^＋η（＇） and B^0 → ρ^0（ω, φ）η（＇）, induced by the vertex QCD corrections, the quark-loops as well as the chromo-magnetic penguins. From the numerical results and phenomenological analysis we find that （a） for B^± → ρ^±η（＇） （B^0 → ρ^0（ω, φ）η（＇）decays, the partial NLO contributions to branching ratios are small （large） in magnitude; and （b） the pQCD predictions for ACP^dir（B^± → ρ^±η（＇）） are consistent with the data, while the predicted .ACP（B^0 → ρ^0（ω）η（＇）） are generally large in magnitude and could be tested by the forthcoming LHCb experiments.     

B →πη（′）, η（′）η（′） decays and NLO contributions in the pQCD approach＊

By employing the perturbative QCD （pQCD） factorization approach, we calculate the full leading and the partial next-to-leading order （NLO） contributions to the seven B →πη（′） and η（′）η（′） decays. For B^＋→ π＋η（′） decays, the pQCD predictions for their decay rates agree very well with the data after the inclusion of the small NLO contributions. For neutral decays, the pQCD predictions are also consistent with the experimental upper limits and can be tested by the LHC experiments. The measured value of dir .Acp^dir（π＋η）= 19±7% can also be accommodated by the pQCD approach.     

Charmless Hadronic Decays B→VV in the Topcolor-Assisted Technicolor Model

Based. On the effective Hamiltonian with the generalized factorization approach, we calculate the branchingratios and CP asymmetries of B → VV decays in the Topcolor-assisted Technicolor (TC2) model. Within the consideredparameter space we find that: (a) for the penguin-dominated B → K* φ and K*0 φ decays, the new physics enhancementsto the branching ratios are around 40%; (b) the measured branching ratios of B →K* φ and K*0φ decays prefer therange of 3 Neffc 5; (c) the SM and TC2 model predictions for the branching ratio B(B →ρ ρ0) are only about halfof the Belle‘s measurement; and (d) for most B → VV decays, the new physics corrections on their CP asymmetries are generally small or moderate in magnitude and insensitive to the variation of mπ and Neffc.     

B→K^＊у/Decay in Top-Quark Two-Higgs-Doublet Model

By employing the QCD factorization approach for the exclusive B→Vу decays, we study the exclusive decay B→K^＊у in the top-quark two-Higgs-doublet mode/（T2HDM）. Within the considered parameter space, we find the following conclusions （a） A hght charged-Higgs boson with a mass about 200 GeV is clearly excluded by the date of B→K^＊у decay, and this lower limit is comparable with that from the inclusive B→X8＊у decay; （b） The theoretical predictions for CP asymmetry of B→K^＊у in the T2HDM is always less than 1% in size; and （c） The isospin symmetry breaking for B→K^＊у decay in the SM and T2HDM considered here is around 6% in size and well consistent with the data and the general expectations.     

Semileptonic decays B/Bs→(D?,D?s)lνl in the PQCD approach with the lattice QCD input

We study the semileptonic B/Bs→(D^?,D^?s)lνl decays in the framework of the Standard Model(SM),by employing the perturbative QCD(PQCD)factorization formalism combined with the lattice QCD input for the relevant transition form factors.We calculate the branching ratios B(B(s)→D^?(s)lνl)with l=(e,μ,τ),the ratios of the branching fractions R(D^?)and R(D^?s),and the physical observables Pτ(D^?(s)),FL(D?(s))and AFB(τ).The“PQCD+Lattice”predictions for B(B→D^?lνl)and R(D^?)agree with the available experimental measurements within errors.For the ratios R(Ds)and R(D^?s),the"PQCD+Lattice"predictions agree with the other predictions.For Pτ(D^?)and FL(D^?),our theoretical predictions agree with the measured values within errors.Our theoretical predictions of the semileptonic B/Bs decays considered could be tested in the near future by the LHCb and Belle II experiments.     

Study of scalar meson a0（980） from B → a0（980）π decays

In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays B^0 → a0^0（980）π^0, a0^＋ （980）π^-, a0^-（980）π^＋ and B^- → a0^0 （980）π^-, a0^- （980）π^0 by employing the perturbative QCD （pQCD） factorization approach at the leading order. We found that （a） the pQCD predictions for the branching ratios are around （0.4-2.8） × 10^-6, consistent with currently available experimental upper limits; （b） the CP asymmetries of B^0→ a0^0（980）π^0 and B^- → a0^- （980）π^0 decays can be large, about （70-80）% for α= 100°.     

B→K_0~*(1430)η~(') decays in the pQCD approach

Based on the assumption of two-quark structure of the scalar meson K*0(1430),we calculate the CP-averaged branching ratios for B→K0*(1430)η(') decays in the framework of the perturbative QCD(pQCD) approach here.We perform the evaluations in two scenarios for the scalar meson spectrum.We find that:(a) the pQCD predictions for Br(B→K*0(1430)η(')) which are about 10-5-10-6,basically agree with the data within large theoretical uncertainty;(b) the agreement between the pQCD predictions and the data in Scenario ...     

B→K_0~*(1430)η~(') decays in the pQCD approach

Based on the assumption of two-quark structure of the scalar meson K*0(1430),we calculate the CP-averaged branching ratios for B→K0*(1430)η(') decays in the framework of the perturbative QCD(pQCD) approach here.We perform the evaluations in two scenarios for the scalar meson spectrum.We find that:(a) the pQCD predictions for Br(B→K*0(1430)η(')) which are about 10-5-10-6,basically agree with the data within large theoretical uncertainty;(b) the agreement between the pQCD predictions and the data in Scenario I is better than that in Scenario II,which can be tested by the forthcoming LHC experiments;(c) the annihilation contributions play an important role for these considered decays.     

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

The annihilation type diagrams are di cult 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 k_T factorization. Although the expansion parameter 1/m_D 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.     

B→Kη~(,) decays in the SM with fourth generation fermions

By employing the perturbative QCD(pQCD) factorization approach, we calculate the new physics contributions to the four B→Kη()decays in the Standard Model(SM) with a fourth generation of fermions(SM4),induced by the loop diagrams involving t quark. Within the considered parameter space of the SM4 we find that:(a) the next-to-leading order(NLO) pQCD predictions for the branching ratios and CP-violating asymmetries in both the SM and SM4 generally agree with the data within one standard deviation;(b) for Br(B→Kη), the inclusion of the fourth generation contributions can improve the agreement between the theoretical predictions and the data effectively;(c) however, for Br(B → Kη) the decrease due to t loops is disfavored by the data; and,(d) the new physics corrections to the CP-violating asymmetries of the considered decays are only about 10%.     

Studies of Bs^0 → η＇η＇ Decays in pQCD Approach

We calculate the CP averaged branching ratios and CP-violating asymmetries for Bs^0 → η＇η＇ and η＇η＇ decays in the perturbative QCD （pQCD） approach here. The pQCD predictions for the C P-averaged branching ratios are Br（Bs^0 → ηη）=（14.2-7.5^＋18.0） ×10^-6,Br（Bs^0 → ηη＇）=（12.4-7.0^＋18.2）×10^-6,and Br（Bs^0 → η＇η＇） =（9.2-4.9^＋15.3）×10^-6, which agree well with those obtained by employing the QCD factorization approach and also be consistent with available experimental upper limits. The gluonic contributions are small in size： less than 7% for Bs →ηηand ηη＇ decays, and around 18% for Bs →η＇η＇ decay. The CP-violating asymmetries for three decays are very small： less than 3% in magnitude.     

Study of W-Exchange Mode D0 → ФK0

We calculate the branching ratio of rare decay D^0→ФK using the perturbative QCD factorization approach based on kT factorization. Our result shows this branching ratio is （8.7 ± 1.4） x 10^-3, which is consistent with experimental data. We hope that the CLEO-C and BES-Ⅲ can measure it more accurately, which will help us to understand QCD dynamics and D meson weak decays.