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.     

New Physics Effects on Rare Decays Bu^＋ → π^＋e^＋e^-, ρ^＋e^＋e^- in a Top Quark Two-Higgs-Doublet Model

Using the form factors from light-cone sum rules, we study the branching ratios and forward-backward asymmetries （FBAs） of the exclusive decays Bu^＋→π^＋e^＋e^- and Bu^＋ →ρ^＋e^＋e^- （e= e,μ） in the standard model （SM） and the top quark two-Higgs-doublet model （T2HDM）. From the numerical results, we find that the new physics contributions cannot provide very large enhancement to the branching ratios and the theoretical predictions are in good agreement with the SM ones. The T2HDM effects on FBAs of these decays are small. Precision measurements of the dilepton invariant mass distributions, especially in the lower dilepton mass region, and the FBAs in the decays Bu^＋ → π^＋ （ρ^＋ ）e^＋ e^- will greatly help in discriminating among the SM and the new physics models.     

Investigation of rare semileptonic B_c→(D_(s,d)~((*))μ~+μ~- decays with non-universal Z' effect

We analyze different decay observables of semileptonic decays B_c→(D_(s,d)~((*)))μ~+μ~-,such as the branching ratio,forward-backward asymmetry,polarization fraction,and lepton polarization asymmetry in the non-universal Z'model.We further study the dependence of the branching fraction to the new model parameters and find that the values of different decay parameters increase in the Z' model,which indicates a possible approach for the search of new physics as well as for the unknown phenomena of the charm B meson.     

Constraints of unparticle physics parameters from K^0-^-K^0 mixing

The neutral kaon meson mixing plays an important role in the test of the Standard Model （SM） and new physics beyond it. Scale invariant unparticle physics induces a flavor changing neutral current （FCNC） transition of m K^0-^-K^0 oscillation at the tree level. In this study, we investigate the scale invariant unparticle physics effects on the m K^0-^-K^0 mixing. Based on the current experimental data, we give constraints of m K0-K0 mixing on the unparticle parameters.     

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.     

Uncertainty Study of Bd（Bs）→γvv Decays

B^0（Bs）→γvv decays are useful to determining the decay constants fB（fBs） and B（Bs） meson wave function. Using the B meson wave function determined in hadronic B（Bs） decays, we study the uncertainties due to the types of B meson wave functions. We find that the branching ratios are sensitive to the type of wave functions and input parameters, but the energy spectrum is independent. The predicted branching ratios are （0.45-1.04）×10^-9 and （2.14-3.27）×10^-8 for B^0 and Bs decay, respectively.     

γ Radiative Decays to Light Quark Jets and Color Octet Mechanism

We study radiative decays of T to light quark jets in nonrelativistic QCD by taking both the color singlet and color octet b^-b operators into consideration. The cut for quark jet energy and cut for the angle between two quark jets are introduced. The sensitivity to the soft and collinear singularities in the loop integrals are greatly reduced by these cuts. With the jet energy cut of about 1 GeV, and the jet angle cut of about 36°, the branching ratio for γ→ rq^- is found to be 8.2 × 10^-4 from color singlet contributions. The color octet contributions could be much larger than that of color singlet, depending on the estimate of the color octet matrix elements. This process may provide a new test for the color octet mechanism in nonrelativistic QCD.     

Can contributions to B_s→l＋l-γ from the magnetic-penguin operator with real photons in the standard model be neglected？

Using the Bs meson wave function extracted from non-leptonic Bs decays, we reevaluate the rare decays Bs→l＋l- γ,（l=e,μ） in the Standard Model, including two kinds of contributions from the magnetic-penguin operator with virtual and real photons. We find that contributions to the exclusive decays from the magnetic-penguin operator b→sγ with real photons, which were regarded as negligible in the previous literature, are large and the branching ratios Bs→l＋l-γ are enhanced by a factor of almost 2. With the predicted branching ratios of the order of 10-8, it is expected that these radiative dileptonic decays will be detected in LHC-b and B factories in the near future.     

Looking for new physics via semi-leptonic and leptonic rare decays of D and D_s

It is well recognized that looking for new physics at lower energy colliders is a path which is complementary to high energy machines such as the LHC.Using the large volume of data collected by BESIII,we may have a unique opportunity to tackle this.In this paper we calculate the branching ratios of the semi-leptonic processes D_s~+ →K~+e~-e~+ and D_s~+ →K~+e~-μ~+,and the leptonic processes D~0→ e~-e~+ and D~0→ e~-μ~+,in the frameworks of the U(1) model,2HDM and unparticle model.It is found that both the U(1) model and 2HDM may influence the semi-leptonic decay rates,but only the U(1) model offers substantial contributions to the pure leptonic decays,and the resultant branching ratio of D~0→e~-μ~+ can be as large as 10~(-7)~10~(-8).This might be observed at the future super τ-charm factory.     

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.     

φ Electro-production in Pomeron Exchange Model

Based on the Pomeron exchange model, elastic production of φ meson in electron-proton interaction is investigated with both linear and non-linear Pomeron trajectories. The numerical calculations of the differential cross section for e p → e‘ p φ are performed. The theoretical predictions show that the dependence of the differentialcross section on virtual photon virtuality, Q2, is of moderation, the change of the energy scale parameter so causes moderate effect on the differential cross section, and the linear trajectory is a good approximation to non-linearity of the Pomeron trajectory, in particular, at small momentum transfer region | t |≤ 0.2 GeV2.     

Effective field theory approach to lepton number violating τ decays

We continue our endeavor to investigate lepton number violating(LNV) processes at low energies in the framework of effective field theory(EFT).In this work we study the LNV tau decays τ~+→l~-P_i~+P_j~+,where l=e,μand P_(i,j)~+denote the lowest-lying charged pseudoscalars π~+,K~+.We analyze the dominant contributions in a series of EFTs from high to low energy scales,namely the standard model EFT(SMEFT),the low-energy EFT(LEFT),and the chiral perturbation theory(χPT).The decay branching ratios are expressed in terms of the Wilson coefficients of dimension-five and-seven operators in SMEFT and the hadronic low-energy constants.These Wilson coefficients involve the first and second generations of quarks and all generations of leptons;thus,they cannot be explored in low-energy processes such as nuclear neutrinoless double beta decay or LNV kaon decays.Unfortunately,the current experimental upper bounds on the branching ratios are too weak to set useful constraints on these coefficients.Alternatively,if we assume the new physics scale is larger than 1 TeV,the branching ratios are well below the current experimental bounds.We also estimate the hadronic uncertainties incurred in applying χPT to τ decays by computing one-loop chiral logarithms and attempt to improve the convergence of chiral perturbation by employing dispersion relations in the short-distance part of the decay amplitudes.     

φElectro-production in Pomeron Exchange Model

Based on the Pomeron exchange model, elastic production of φ meson in electron-proton interaction is investigated with both linear and non-linear Pomeron trajectories. The numerical calculations of the differential cross section for e＋p→e＇ ＋p＋ φ are performed. The theoretical predictions show that the dependence of the differential cross section on virtual photon virtuality, Q^2, is of moderation, the change of the energy scale parameter so causes moderate effect on the differential cross section, and the linear trajectory is a good approximation to non-linearity of the Pomeron trajectory, in particular, at small momentum transfer region ｜t｜≤ 0.2 GeV^2.     

Sigma Meson Production in Nuclear Reactions

The sigma meson production in p ＋ ^12C and p A- ^40Ca reactions at the incident energy Ep = 1.5 GeV is investigated within the Quantum Molecular Dynamics model. The simulation results indicate a distinctive A dependence of the sigma production, that is, the increase of A is followed by an increase of the production cross sections. We find that the σ meson production in proton-induced reactions is strongly medium-dependent, and the produced σ mesons decaying in a denser medium experience a stronger mass shift towards lower masses. This mass shift is an experimentally accessible observable in the final state pion pairs, which do not suffer from reabsorption by the surrounding nucleons. It is pointed out that the ratio of measured sigma cross sections as a function of the sigma invariant-mass from various reactions is a good probe to explore the existence of the σ meson in a dense nuclear environment.     

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.     

Resonance properties from a coupled channel meson exchange model

In this talk, I present the results on the pole structure of pion-nucleon scattering in an analytic model based on meson exchange. The analytic properties of scattering amplitudes provide important information. Besides the cuts, the poles and zeros on the different Riemann sheets determine the global behavior of the amplitude on the physical axis. Pole positions and residues allow for a parameterization of resonances in a well-defined way, free of assumptions for the background and energy dependence of the resonance part. This is a necessary condition to relate resonance contributions in different reactions.     

Radiative Decays of Charmonium into Light Mesons

We apply perturbative QCD to the radiative decays of charmonia J/ψ and χcJ into light mesons. We perform a complete numerical calculation for the quark-gluon loop diagrams involved in these processes. The calculated J/ψ decay branching ratios into p-wave mesons f2（1270） and f1（1285） fit the data well, while that of fo（980） （if treated as an ss meson） is predicted to be 1.6×10^-4, which implies that f0（1710） can not be the ss or （uu＋dd）/√2 meson. Decays of p-wave charmonia χcJ→ρ（ω;φ）γ （J = 0, 1, 2） are also studied, and the branching ratio of χc1→ργ is predicted to be 1.4×10^-5, which may be tested by CLEO-c collaboration and BESlg collaboration with future experiments.     

Measuring D~0-~0mixing in D→f_0(980)K~* and more

We investigate the D0-0 mixing through the doubly Cabibbo suppressed (DCS) channel D0 →f0(980)K0 and its charge conjugate channel, in which the K0 meson is reconstructed in both K π- and KSπ0 final state. Although the decay D0 →f0(980)K* has a small branching ratio, the final state mesons are relatively easy to identify. The f0(980) meson can be replaced by the S-wave π π- state, or a longitudinally polarized vector meson ρ0. All mixing parameters, including the mass difference and decay width difference,can be extracted by studying the time-dependent decay width of these channels. We show that the method is valid in all regions for mixing parameters and it does not depend on the strong phase difference.     

Measuring DO-D-O mixing in D→Fo(980)K* and more

We investigate the DO-D-O mixing through the doubly Cabibbo suppressed (DCS) channel DO→fO(980)K*O and its charge conjugate channel,in which the K*O meson is reconstructed in both K+π- and KsπO final state.Although the decay DO→ fo(980)K* has a small branching ratio,the final state mesons are relatively easy to identify.The fo(980) meson can be replaced by the S-wave π+π- state,or a longitudinally polarized vector meson pO.All mixing parameters,including the mass difference and decay width difference,can be extracted by studying the time-dependent decay width of these channels.We show that the method is valid in all regions for mixing parameters and it does not depend on the strong phase difference.