Charmonium dissociation in collisions with φ mesons in hadronic matter

The φ-charmonium dissociation reactions in hadronic matter are studied.Unpolarised cross sections forφJ/ψ→D_s~-D_s~+,φJ/ψ→D_s~(*-)D_s~+ or D_s~-D_s~(*+),φJ/ψ→D_s~(*-)D_s~(*+),φψ'→D_s~-D_s~+,φψ'→D_s~(*-)D_s~+ or D_s~-D_s~(*+),φψ'→D_s~(*-)D_s~(*+),φχ_c→D_s~-D_s~+,φχ_c→D_s~(*-)D_s~+ or D_s~-D_s~(*+) and φχ_c→D_s~(*-)D_s~(*+) are calculated in the Born approximation,in the quark-interchange mechanism and with a temperature-dependent quark potential.The potential leads to remarkable temperature dependence of the cross sections.With the cross sections and the φ distribution function we calculate the dissociation rates of the charmonia in interactions with the φ meson in hadronic matter.The dependence of the rates on temperature and charmonium momentum is relevant to the influence of φ mesons on charmonium suppression.     

Searching for Electrical Dipole and Chromodipole Moments of a Charm Quark in J／ψ→γφφ Decay

We propose a scheme to search for the electrical dipole moments (EDMs) and chromodipole moments (CDMs) of a charm quark in the decay J/ψ→γφφ based on J/ψ data samples accumulated on the Beijing Electron Positron Collider (BEPC). The EDM and CDM interactions are introduced in this decay and then we relate them to some CP asymmetrical observables, which are predicted in the valence quark model. We propose a method to hunt for these values by measuring associated CP asymmetrical observables, and we also discuss the prospect of such measurement on the BEPC.     

J／φ→γBB Decays and the Quark—pair Creation Model

We generalize the quark-pair creation model to a study of the radiative decays J/φ→γBB by assuming that the u.d,or s quark pairs are created with the same interaction strength,From the calculation of the ratio of the decay widths （J/φ→γpp)/Γ（J/φ→pp),we extract the quark-pari creation strength gI=15.40GeV,Based on the SU(6)spin-flavour basis and the “uds” basis,the radiative decay branching ratios cotaining strange baryons are evaluated.Measurements for these decay widths from the BESII data are suggested.     

Large SU（3） Symmetry Breaking in J／ψ→BB Decays

Large SU(3) symmetry breaking effects in J/ψ→BB decay processes are discussed using the Mark I,Mark II,DM2 and the recent data from BES Collaboration.     

Study of C parity violating and strangeness changing J/ψ→PP weak decays

Although J/ψ weak decays are rare,they are possible within the standard model of elementary particles.Inspired by the potential prospects of the future intensity frontier,the C parity violating J/ψ→πη~((')),ηη' decays and the strangeness changing J/ψ→πK,Kη~((')) decays are studied via the perturbative QCD approach.It is determined that the J/ψ→ηη' decays have relatively large branching ratios,approximately on the order of 10~(-11),which might be within the measurement capability and sensitivity of the future STCF experiment.     

Recent results on light hadron spectroscopy from BES Ⅱ

We reported the observation of Y(2175) in φf0(980) mass spectrum in J/ψ→ηφf0(980) with f0(980)→π+π- and the observation of a broad 1-- resonance of K+K-mass in J/ψ→K+K-π0. The results from the partial wave analyses of Jψ→γπ+π- and γπ0π0, as well as J/ψ→pK-∧. are also presented.     

Further insights into the “ρπ puzzle”

Based on a systematic investigation of J/ψ(ψ) → VP,where V and P stand for light vector and pseudoscalar mesons,we identify the role played by the electromagnetic(EM) transitions and intermediate meson loop transitions,which are essential ingredients for understanding the J/ψ and ψ couplings to VP.We show that on the one hand,the EM transitions have relatively larger interferences in ψ→ρπ and K*K+c.c.as explicitly shown by vector meson dominance(VMD).On the other hand,the strong decay of ψ receives relatively larger destructive interferences from the intermediate meson loop transitions.By identifying these mechanisms in an overall study of J/ψ(ψ)→VP,we provide a coherent understanding of the so-called "ρπ puzzle".     

ρ-ω mixing in J/ψ→VP decays

The study of ρ-ω mixing has mainly focused on vector meson decays with isospin I = 1, namely theρ(ω)→π+π- process. In this paper, we present a study of ρ-ω mixing in ρ(ω)→π+π-π0(I = 0) using a flavor parameterization model for the J/ψ→VP process. By fitting a theoretical framework to PDG data, we obtain the SU(3)-breaking effect parameters sV = 0.03±0.12, sP = 0.17±0.17 and the ρ-ω mixing polarization operatorΠρω =(0.006±0.011) GeV2. New values are found for the branching ratios when the mixing effect is incorporated:Br(J/ψ→ωπ0)=(3.64±0.37)×10-4, Br(J/ψ→ωη)=(1.48±0.17)×10-3, Br(J/ψ→ωη)=(1.55±0.56)×10-4, these are different from the corresponding PDG2012 values by 19%, 15% and 15%, respectively.     

Transition magnetic moments of J~P=3/2~+ decuplet to J~P=1/2~+ octet baryons in the chiral constituent quark model

In light of the developments of the chiral constituent quark model(χ~(CQM)) in studying low energy hadronic matrix elements of the ground-state baryons, we extend this model to investigate their transition properties.The magnetic moments of transitions from the J~P=3/2~+ decuplet to J~P=1/2~+ octet baryons are calculated with explicit valence quark spin, sea quark spin and sea quark orbital angular momentum contributions. Since the experimental data is available for only a few transitions, we compare our results with the results of other available models. The implications of other complicated effects such as chiral symmetry breaking and SU(3) symmetry breaking arising due to confinement of quarks are also discussed.     

A Model of Fermion Masses and Flavor Mixings with Family Symmetry SU(3)U(1)

The family symmetry SU(3)U(1) is proposed to solve flavor problems about fermion masses and flavor mixings.It is breaking is implemented by some flavon fields at the high-energy scale.In addition a discrete group Z 2 is introduced to generate tiny neutrino masses,which is broken by a real singlet scalar field at the middle-energy scale.The low-energy effective theory is elegantly obtained after all of super-heavy fermions are integrated out and decoupling.All the fermion mass matrices are regularly characterized by four fundamental matrices and thirteen parameters.The model can perfectly fit and account for all the current experimental data about the fermion masses and flavor mixings,in particular,it finely predicts the first generation quark masses and the values of θ l 13 and J l CP in neutrino physics.All of the results are promising to be tested in the future experiments.     

Pion properties at finite isospin chemical potential with isospin symmetry breaking

Pion properties at finite temperature, finite isospin and baryon chemical potentials are investigated within the SU(2) NJL model. In the mean field approximation for quarks and random phase approximation fpr mesons, we calculate the pion mass, the decay constant and the phase diagram with different quark masses for the u quark and d quark, related to QCD corrections, for the first time. Our results show an asymmetry between μI 0 and μI 0 in the phase diagram, and different values for the charged pion mass(or decay constant) and neutral pion mass(or decay constant) at finite temperature and finite isospin chemical potential. This is caused by the effect of isospin symmetry breaking, which is from different quark masses.     

Production of hidden-charm and hidden-bottom pentaquark states in electron-proton collisions

Electro-production of several pentaquark states is investigated in this study.The eSTARlight package is adapted to study the electro-production of J/ψand γ(1S)via pentaquark P_cand P_bresonance channels in ep→eJ/ψp and ep→eγ(1S)p scattering processes at the proposed electron-ion colliders(EICs).The results obtained in this study are compared to those of non-resonance t-channels,which are described in the pomeron exchange model developed in our studies.Some pseudo-rapidity and rapidity distributions of J/ψand γ(1S)are presented for the proposed EICs,including EicC and EIC-US.It is found that EicC is a good platform to identify P_b states in the future.     

η_b decay into charmonium in association with c pair

We calculate the inclusive decay rates of ηb into charmonium via double c pairs for S-and P-wave states ηc,J/ψ and χcJ within the framework of non-relativistic QCD(NRQCD) factorization at leading order in αs.Besides calculating the contributions of the color-singlet channels ηb→c[2S+1SL(1)]+c,the effects of c pair in the color-octet configurations are also considered.We find that ηb→c[3S1(8)]+c make a small contribution to Br(ηb→J/ψ(ηc)+c).While in the ηb→χcJ+c case,the color octet contributions are significant,for they are of the same αs4vc5 order as the color-singlet processes.We predict Br(ηb→J/ψ(ηc)+c)=2.99(2.75)×10-5 for S-wave states J/ψ and ηc,and Br(ηb→χcJ+c)=(4.37,3.40,2.83)×10-5(for J =0,1,2) for P-wave states χcJ.In the end,we also find Br(ηb→ cc) is almost saturated by ηb decay into charmonium in association with c pair from the point of view of duality.     

ηb decay into charmonium in association with c(c) pair

We calculate the inclusive decay rates of ηb into charmonium via double cc pairs for S- and P-wave states ηc, J/ψ and χcJ within the framework of non-relativistic QCD (NRQCD) factorization at leading order in αs. Besides calculating the contributions of the color-singlet channels ηb→c(c)[2S+1Sl(1)]+c(c), the effects of c(c) pair in the color-octet configurations are also considered. We find that ηb→c(c)[3S1(8)]+c(c) make a small contribution to Br(ηb→J/ψ(ηc)+c(c)). While in ther ηb→χcJ+c(c) case, the color octet contributions are significant, for they are of the same αs4vc5 order as the color-singlet processes. We predict Br(ηb → J/ψ(ηc)+c(c)) = 2.99(2.75) × 10-5 for S-vrave states J/ψ and ηc, and Br(ηb→χcJ +c(c))= (4.37,3.40,2.83)×10-5 (for J = 0,1,2) for P-wave states χcJ. In the end, we also find Br(ηb → c(c)c(c)) is almost saturated by ηb decay into charmonium in association with cc pair from the point of view of duality.     

Further insights into the ＂ρπ puzzle＂

Based on a systematic investigation of J/ψ（ψ＇）→VP, where V and P stand for light vector and pseudoscalar mesons, we identify the role played by the electromagnetic （EM） transitions and intermediate meson loop transitions, which are essential ingredients for understanding the J/ψ and ψ＇ couplings to VP. We show that on the one hand, the EM transitions have relatively larger interferences in ψ＇→ρπ and K^＊^-K ＋c.c. as explicitly shown by vector meson dominance （VMD）. On the other hand, the strong decay of ψ＇ receives relatively larger destructive interferences from the intermediate meson loop transitions. By identifying these mechanisms in an overall study of J/ψ（ψ＇） → VP, we provide a coherent understanding of the so-called ＂ρπ puzzle＂.     

Perturbative QCD for J/ψ inclusive production via initial state radiation in e~+e~- collisions

The process e+e-→J/ψ+X with the center-of-mass(CM)energy in the range from 3.7 to 10.6 GeV is calculated up to the next-to-leading order(NLO)in quantum chromodynamics(QCD).At 10.6 GeV,the result is consistent with the experimental result from Belle.However,the predictions are much smaller than the background in the measurements at BESIII in the low CM energy range from 3.7 to 4.6 GeV.This indicates that the convergence of the QCD perturbative expansion becomes worse as the CM energy is closer to the inclusive J/ψ production threshold.For a further study of the QCD mechanism of J/ψ production in e~+e~-collisions with different CM energies,the initial state radiation effect of e~+e~-→J/ψ +gg and e~+e~-→J/ψ+cc are calculated in QCD NLO.The results are plotted and the number of events for different CM energy bins are provided for SuperKEKB.This provides a method to precisely test the validity of perturbative predictions for J/ψ production in future measurements.     

J/ψ Inclusive Photon Spectrum at BESIII

With a 15M J/ψ inclusive Monte Carlo sample, the absolute branching fraction of J/ψ→γ\η' from the J/ψ inclusive photon spectrum is measured to be Br(J/ψ→γ\η')=(4.68±0.08±0.27)×10^-3, which is in good agreement with the input value. The J/ψ→γf_J(2220) is also searched for using the same sample. Under our assumptions, the statistical significances of J/ψ→γf_J(2220) are larger than 7\σ.     

Study of ■ decay parameter in J/ψ→Λ■ decay

The helicity amplitudes for J/ψ→Λ■ and the relevant background decays are presented for measuring the ■ decay parameter α (■→π ) in J/ψ→Λ■. The Monte Carlo (MC) simulations based on the helicity amplitudes information are carried out. The likelihood fit method to determine the ■ decay parameter is presented. Based on the MC generated sample, the sensitivity of the measurement for α has been estimated, which shows that the J/ψ→Λ■ channel can be used to measure the ■ decay parameter α (■→π ) well.