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).

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.

Nonfactorizable B→xcoK Decay and QCD Factorization

We study the unexpectedly large rate for the factorization-forbidden decay B →xcoK within the QCD factorization approach. We use a non-zero gluon mass to regularize the infrared divergences in vertex corrections. The end-point singularities arising from spectator corrections are regularized and carefully estimated by the off-shellness of quarks. We find that the contributions arising from the vertex and leading-twist spectator corrections are numerically small, and the twist-3 spectator contribution with chiral enhancement and linear end-point singularity becomes dominant. With reasonable choices for the parameters, the branching ratio for B → XcoK decay is estimated to be in the range （2 ～ 4）× 10^-4, which is compatible with the Belle and BaBar data.

B→D_s^((*))η^(('))Decays in Perturbative QCD

In this paper,we calculate the branching ratios for B^+→D_s^+η,B^+→D_s^+η′,B^+→D_s^(*+)η and B^+→D_s^(*+)η′decays by employing the perturbative QCD (pQCD) factorization approach.Under the two kinds of η-η′ mixingschemes,the quark-flavor mixing scheme and the singlet-octet mixing scheme,we find that the calculated branchingratios agree well with the currently available experimental upper limits.We also consider the so called 'f_D_s puzzle',byusing two groups of parameters about the D_s^((*)) meson decay constants,that are f_D_s = 241 MeV,f_D_s~* = 272 MeV andf_D_s = 274 MeV,f_D_s~* = 312 MeV,to calculate the branching ratios for the considered decays.We find that the resultschange 30% by using these two different kinds of paramters.

B→ X8γ, X8l＋l- Decays and Constraints on Mass Insertion Parameters in MSSM

In this paper, we study the upper bounds on the mass insertion parameters （δAB^q）ij in the minimal super symmetric standard model. We found that the information from the measured branching ratio of B→ X8γ, X8l＋l- decay can help us to improve the upper bounds on the mass insertions parameters （δAB^u,d）3j,i3 Some regions allowed by the data of Br（B→ X8γ） are excluded by the requirement of an SM-like C7γ （rnb） imposedby the data of Br（B→ X8γ, X8l＋l- ）.

Triangle mechanism in the decay process B_(0)→J/ψK^(0)f_(0)(980)(a_(0)(980))

The role of the triangle mechanism in the decay processes B_(0)→J/ψK^(0)f_(0)→J/ψK^(0)π^(+)π^(-)and B_(0)→J/ψK^(0)a_(0)→J/ψK^(0)π^(0)ηis probed.In these processes,the triangle singularity appears from the decay of B_(0)intoJ/ψ∅K^(0),and then,∅decays intoK^(0)K^(0)andK^(0)K^(0)merged into f_(0)or a_(0),which finally decay intoπ^(+)π^(-)andπ^(0)η,respectively.We find that this mechanism leads to a triangle singularity around M_(inv)(K^(0)f_(0)(a_(0)))≈1520 MeV and gives sizable branching fractions Br(B_(0)→J/ψK^(0)f_(0)→J/ψK^(0)π^(+)π^(-))=7.67×10^(-7)and Br(B_(0)→J/ψK^(0)a_(0)→J/ψK^(0)π^(0)η)=1.42×10^(-7).This investigation can help us obtain the information of the scalar mesonf_(0)(980)or a_(0)(980).

Study of scalar meson a_0(980) from B→a_0(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→f_0(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→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.

Direct CP violation of three body decay processes from the resonance effect

The physical state of ρ−ω−φ mesons can be mixed using the unitary matrix.The decay processes ω→π^(+)π^(−)and φ→π^(+)π^(−)originate from isospin symmetry breaking.The ρ−ω,ρ−φ,and ω−φ interferences lead to a resonance contribution to produce strong phases.CP violation is considered from isospin symmetry breaking due to the new strong phase of the first order.CP violation can be enhanced greatly for the decay process B^(0)→π^(+)π^(−)η^((′))when the invariant masses of π^(+)π^(−) pairs are in the area around the ω resonance range and φ resonance range in perturbative QCD.We also discuss the possibility of searching for the predicted CP violation at the LHC.

Probing new physics in B → J/ψπ~0 decay

We calculate the branching ratio of B → J/ψπ0 with a mixed formalism that combines the QCDimproved factorization and the perturbative QCD approaches.The result is consistent with experimental data.The quite small penguin contribution in B → J/ψπ0 decay can be calculated with this method.We suggest two methods to extract the weak phase β.One is through the dependence of the mixing induced CP asymmetry SJ/ψπ0 on the weak phase β,the other is from the relation of the total asymmetry ACP with the weak phase β.Our results show that the deviation ΔSJ/ψπ0 of the mixing induced CP asymmetry from sin（-2β） is of O（10-3） and has much less uncertainty.The above O（10-3） deviation can provide a good reference for identifying new physics.

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→a1（1260）K＊, bl （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→ФK＊, pK＊ also happen in B→a1K＊ decays, while they do not happen in B→blK＊ decays. Here the contributions from the annihilation diagrams play an important role in explaining the larger transverse polarizations in the B→alK＊ decays, while they are not sensitive to the polarizations for the B→blK＊ decays. （c） Our predictions for the direct CP-asymmetries agree well with the QCDF results within errors. The decays B-0→b＋K＊-, B-→b0/1K＊- have larger direct CP-asymmetries, which could be measured by the present LHCb experiment and the forthcoming Super-B experiment.

Impact of a_(0)^(0)(980)-f_(0)(980) mixing on the localized CP violations of the B^(-)→K^(-)π^(+)(π)^(-) decay

In the framework of the QCD factorization approach,we study the localized CP violations of the B^(-)→K^(-)π^(+)(π)^(-)decay with and without the a_(0)^(0)(980)-f_(0)(980) mixing mechanism and observe that the localized CP violation can be enhanced by this mixing effect when the mass of the π^(+)(π)^(-)pair is in the vicinity of the f_(0)(980) resonance.The corresponding theoretical prediction results are A_(CP)(B^(-)→Kf_(0)→K^(-)π^(+)(π)^(-))=[0.126,0.338](0.232±0.106 with the central value form) and A_(CP)(B^(-)→K^(-)f_(0)(a_0)→K^(-)π^(+)(π)^(-))=[0.230,0.615](0.423±0.193 with the central value form),respectively.Meanwhile,we also calculate the branching fraction of the B^(-)→K^(-)f_(0)(980)→K^(-)π^(+)(π)^(-)decay,which is consistent with the experimental results.We suggest that the a_(0)^(0)(980)-f_(0)(980) mixing mechanism should be considered when theoretically and experimentally studying the CP violation of the B or D meson decays.

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.

The B→πlv_l semileptonic decay within the LCSR approach under heavy quark effective field theory

The heavy quark effective field theory(HQEFT)provides an effective way to deal with heavy meson decays.In this paper,we adopt two different correlators to derive the light-cone sum rules(LCSR)for the B→πtransition form factors(TFFs)in the framework of HQEFT.We label the two LCSR results as LCSR-u and LCSR-R,which stand for the conventional correlator and the right-handed correlator.We observe that the correlation parameter|ρRU|for the branching ratio B(B→πlv_l)is^0.85,implying a consistency of LCSRs with the other correlators.Furthermore,we obtain|V_(ub)|_(LCSR-u)=(3.45_(-0.20)^(+0.28)±0.13_(exp))×10^(-3)and|V_(ub)|_(LCSR-R)=(3.38_(-0.16)^(+0.22)±0.12_(exp))×10^(-3).We also obtain R_π|_(LCSR-u)=0.68_(-0.09)^(+0.10)and R_π|_(LCSR-R)=0.65_(-0.11)^(+0.13),both of which agree with the lattice QCD predictions.Thus,HQEFT provides a useful framework for studying B meson decays.Moreover,by using the right-handed correlator,the twist-2 terms are dominant in TFF f^+(q^2),as their contribution is over^97%in the whole q^2 region,while the large twist-3 uncertainty of the conventional correlator is greatly suppressed.Hence,the LCSR-R predictions can be used to test the properties of the various models for the pion twist-2 distribution amplitudes.

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 ofs0 → K0＊0 （1430）η ands0→ 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.

A multi-charged particle model with local U(1)_(μ-τ) to explain muon g-2,flavor physics,and possible collider signature

We consider a model with multi-charged particles,including vector-like fermions,and a charged scalar under a local U(1)_(μ−τ) symmetry.We search for an allowed parameter region explaining muon anomalous magnetic moment(muon g−2)and b→sℓ^(+)ℓ^(−) anomalies,satisfying constraints from the lepton flavor violations,Z boson decays,meson anti-meson mixing,and collider experiments.Via numerical analysis,we explore the typical size of the muon g−2 and Wilson coefficients to explain the b→sℓ^(+)ℓ^(−) anomalies in our model when all other experimental constraints are satisfied.Subsequently,we discuss the collider physics of the multicharged vectorlike fermions,considering a number of benchmark points in the allowed parameter space.

Potential pollution of the Kπ-puzzle by the isospin-breakingπ^(0)-η-η′mixing effect

The influence of the isospin-breakingπ^(0)-η-η′mixing effect on the CP-asymmetries of B→Kπprocesses is examined for the first time.It is found that this mixing effect presents significant uncertainty for both the CP-asymmetry sum rule of B→Kπprocesses and the CP-asymmetry difference of B+→K+π^(0)and B0→K+π-,potentially obscuring the significance of the Kπ-puzzle.As the correction caused by theπ^(0)-η-η′mixing effect is highly dependent on four strong non-perturbative phases,a definitive conclusion is currently unavailable.

The ■_(s)^(0)→J/ψπ^(0)η decay and the a_(0)(980)-f_(0)(980) mixing

We study the ■_(s)^(0)→J/ψf_(0)(980) and ■_(s)^(0)→J/ψa_(0)(980) reactions,and pay attention to the different sources of iso spin violation and mixing of f_(0)(980) and a_(0)(980) resonances where these resonances are dynamically generated from meson-meson interactions.We find that the main cause of isospin violation is isospin breaking in the meson-meson transition T matrices,and the other source is that the loops involving kaons in the production mechanism do not cancel due to the different masses of charged and neutral kaons.We obtain a branching ratio for a_(0)(980)production of the order of 5×10^(-6).Future experiments can address this problem,and the production rate and shape of the π^(0)η mass distribution will definitely help to better understand the nature of scalar resonances.

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%.