Is J~(PC)=3~(-+) molecule possible?

The confirmation of charged charmonium-like states indicates that heavy quark molecules should exist.Here we discuss the possibility of a molecule state with J P C= 3-+. In a one-boson-exchange model investigation for the S wave C = + D* ˉD*2states, one finds that the strongest attraction is in the case J = 3 and I = 0 for bothπ and σ exchanges. Numerical analysis indicates that this hadronic bound state might exist if a phenomenological cutoff parameter around 2.3 Ge V(1.5 Ge V) is reasonable with a dipole(monopole) type form factor in the one-pionexchange model. The cutoff for binding solutions may be reduced to a smaller value once the σ exchange contribution is included. If a state around the D* ˉD*2threshold(≈4472 Me V) in the channel J/ψω(P wave) is observed, the heavy quark spin symmetry implies that it is not a cˉc meson and the J P C are likely to be 3-+.     

The study of gluon energy loss in cold nuclear matter from J/ψ production

The energy loss effects of the incident quark, gluon, and the color octet ccˉ on J/ψ suppression in p-A collisions are studied by means of the experimental data at E866, RHIC, and LHC energy. We extracted the transport coefficient for gluon energy loss from the E866 experimental data in the middle x F region(0.20 x F 0.65) based on the Salgado-Wiedemann(SW) quenching weights and the recent EPPS16 nuclear parton distribution functions together with nCTEQ15. It was determined that the difference between the values of the transport coefficient for light quark, gluon, and heavy quark in cold nuclear matter is very small. The theoretical results modified by the parton energy loss effects are consistent with the experimental data for E866 and RHIC energy, and the gluon energy loss plays a remarkable role on J/ψ suppression in a broad variable range. Because the corrections of the nuclear parton distribution functions in the J/ψ channel are significant at LHC energy level, the nuclear modification due to the parton energy loss is minimal. It is worth noting that we use the color evaporation model(CEM) at leading order to compute the p-p baseline, and the conclusion in this paper is CEM model dependent.     

Strange quarkonium states at BESⅢ

We present physics opportunities and topics with the s states(strangeonia)that can be studied with the BES detector operating at the BEPC collider.Though the φ and η/ states have long been established experimentally,only a handful of strangeonia are well known,in contrast to the rich ccharmoium system.An overview of the s states and their experimental status is presented in this paper.The BES experiment has collected the world’s largest samples of J/ψ,ψ(2S),ψ(3770),and direct e+e-annihilations at energies below the J/ψand above 3.8 Ge V,and will continue to accumulate high quality,large integrated luminosity in theτ-charm energy region.These data,combined with the excellent performance of the BESⅢ detector,will offer unprecedented opportunities to explore the s system.In this paper we describe the experimental techniques to explore strangeonia with the BESⅢ detector.     

Glueball spectrum from N_f=2 lattice QCD study on anisotropic lattices

The lowest-lying glueballs are investigated in lattice QCD using N_f = 2 clover Wilson fermions on anisotropic lattices. We simulate at two different and relatively heavy quark masses, corresponding to physical pion masses of mπ～938 MeV and 650 MeV. The quark mass dependence of the glueball masses has not been investigated in the present study. Only the gluonic operators built from Wilson loops are utilized in calculating the corresponding correlation functions. In the tensor channel, we obtain the ground state mass to be 2.363(39) GeV and 2.384(67)GeV at mπ～938 MeV and 650 MeV, respectively. In the pseudoscalar channel, when using the gluonic operator whose continuum limit has the form of ∈_ijkTrB_iD_jB_k, we obtain the ground state mass to be 2.573(55) GeV and 2.585(65) GeV at the two pion masses. These results are compatible with the corresponding results in the quenched approximation. In contrast, if we use the topological charge density as field operators for the pseudoscalar, the masses of the lowest state are much lighter(around 1 GeV) and compatible with the expected masses of the flavor singlet qq meson. This indicates that the operator ∈ijk TrBiDjBk and the topological charge density couple rather differently to the glueball states and qq mesons. The observation of the light flavor singlet pseudoscalar meson can be viewed as the manifestation of effects of dynamical quarks. In the scalar channel, the ground state masses extracted from the correlation functions of gluonic operators are determined to be around 1.4-1.5 GeV, which is close to the ground state masses from the correlation functions of the quark bilinear operators. In all cases, the mixing between glueballs and conventional mesons remains to be further clarified in the future.     

Next-to-leading order QCD corrections to the decay of Higgs to vector meson and Z boson

The exclusive decay of the Higgs boson to a vector meson(J/ψ or Υ(1 S)) and Z boson is studied in this work. The decay amplitudes are separated into two parts in a gauge invariant manner. The first part comes from the direct coupling of the Higgs boson to the charm(bottom) quark and the other from the HZZ*or the loop-induced HZγ*vertexes in the standard model. While the branching ratios from the direct channel are much smaller than those of the indirect channel, their interference terms give nontrivial contributions. We further calculate the QCD radiative corrections to both channels, which reduce the total branching ratios by around 20% for both J/ψ and Υ(1S) production. Our results provide a possible chance to check the SM predictions of the Hcc(Hbb)coupling and to seek for hints of new physics at the High Luminosity LHC or future hadron colliders.     

Phase structures of neutral dense quark matter and applicationto strange stars

In the contact interaction model,the quark propagator has only one solution,namely,the chiral symmetry breaking solution,at vanishing temperature and density in the case of physical quark mass.We generalize the condensate feedback onto the coupling strength from the 2 flavor case to the 2+1 flavor case,and find the Wigner solution appears in some regions,which enables us to tackle chiral phase transition as two-phase coexistences.At finite chemical potential,we analyze the chiral phase transition in the conditions of electric charge neutrality andβequilibrium.The four chemical potentials,μ_u,μ_d,μ_s and He,are constrained by three conditions,so that one inde-pendent variable remains:we choose the average quark chemical potential as the free variable.All quark masses and number densities suffer discontinuities at the phase transition point.The strange quarks appear after the phase trans-ition since the system needg more energy to produce a d.-quark than an s-quark.Taking the EOS as an input,the TOV equations are solved numerically,and we show that the mass--radius relation is sensitive to the EOS.The max-imum mass of strange quark stars is not susceptible to the parameter Aq we introduced.     

Calculation of disconnected quark loops in lattice QCD

Calculation of disconnected quark loops in lattice QCD is very time consuming. Stochastic noise methods are generally used to estimate these loops. However, stochastic estimation gives large errors in the calculations of disconnected diagrams. We use the symmetric multi-probing source(SMP) method to estimate the disconnected quark loops, and compare the results with the Z(2) noise method and the spin-color explicit(SCE) method on a quenched lattice QCD ensemble with lattice volume 12~3× 24 and lattice spacing a ≈ 0.1 fm.. The results show that the SMP method is very suitable for the calculation of pseudoscalar disconnected quark loops. However, the SMP and SCE methods do not have an obvious advantage over the Z(2) noise method in the evaluation of the scalar disconnected loops.     

New spectral representation and evaluation of f π and the quark condensate \left\langle {\bar qq} \right\rangle in the terms of string tension

New spectral representations for f _π and chiral condensate are derived in QCD and used for calculations in the large-N _c limit. Both quantities are expressed in this limit through string tension σ and gluon correlation length T _g without fitting parameters. As a result, one obtains $\left\langle {\bar qq} \right\rangle = - N_c \sigma ^2 T_g a_1 $ , $f_\pi = \sqrt {N_c } \sigma T_g a_2 $ , with a ₁=0.0823, a ₂=0.30. Taking σ=0.18 GeV² and T _g=1 GeV^?1, as known from analytic and lattice calculations, this yields $\left\langle {\bar qq} \right\rangle $ (μ=2 GeV)=?(0.225 GeV)³, f _π=0.094 GeV, which is close to the standard values.     

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.     

The effect of higher-dimensional operators in K → ππ decays

We reexamine the weak ΔS = 1 sector by including higher-dimensional four-quark operators in the lowenergy effective Lagrangian ? _eff ^ΔS=1 . The introduction of a physical cut-off Λ ～- 1 GeV as an effective mass scale in QCD allows for a systematic expansion in powers of p/Λ where p denotes some external quark momentum. Within this framework analytical expressions for the higher-dimensional operators are obtainable. By means of the chiral quark model we evaluate K → ππ matrix elements of L _eff ^ΔS=1 and identify the corrections to the isospin decay channels g ^(1/2) and g ^(3/2). While little affecting ΔI = 1/2 transitions the effect is substantial in the ΔI = 3/2 case where it amounts to a 40% enhancement numerically.     

Tuning and validation of hadronic event generator for R value measurements in the tau-charm region

To measure the R value in an energy scan experiment with e⁺e^- collisions, precise calculation of initial state radiation is required in the event generators. We present an event generator for this consideration, which incorporates initial state radiation effects up to second order accuracy. The radiative correction factor is calculated using the totally hadronic Born cross section. The measured exclusive processes are generated according to their cross sections, while the unknown processes are generated using the LUND Area Law model, and its parameters are tuned with data collected at √s=3.65 GeV. The optimized values are validated with data in the range √s=2.2324-3.671 GeV. These optimized parameters are universally valid for event generation below the DD threshold.     

Sound velocity in dense stellar matter with strangeness and compact stars

The phase state of dense matter in the intermediate density range (\begin{document}$\sim$\end{document}1-10 times the nuclear saturation density) is both intriguing and unclear and can have important observable effects in the present gravitational wave era of neutron stars. As matter density increases in compact stars, the sound velocity is expected to approach the conformal limit (\begin{document}$c_s/c=1/\sqrt{3}$\end{document}) at high densities and should also fulfill the causality limit (\begin{document}$c_s/c<1$\end{document}). However, its detailed behavior remains a prominent topic of debate. It was suggested that the sound velocity of dense matter could be an important indicator of a deconfinement phase transition, where a particular shape might be expected for its density dependence. In this work, we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars as well as in neutron stars and quark stars. Various conditions are employed for the hadron-quark phase transition with varying interface tension. We find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase, in addition to a deconfinement phase transition. Moreover, it leads to a more compact star with a similar mass. We then propose a new class of quark star equation of states, which can be tested by future high-precision radius measurements of pulsar-like objects.     

ANALYSIS OF HADRONIC EVENTS

In this paper I summarize some results obtained from analyses of hadronic final state events. The analyzed data sample comes from Mark-J collaboration and covers an energy range from √S=12GeV to √S =46.78GeV. The integrated luminosity is 128.06Pb^－1. We can search for production of open top quarks and toponium by measuring the total hadronic crossection R =3.85±0.02±0.12 was measured in the above mentioned energy range. It is consistent with R≈3.9 as expected from QCD for five different quark flavors. We search for the narrow bound states of the toponium from 39.79GeV to 46.78GeV. The most prominent resonance signal is at a c.m. energy √S=45.12±0.04GeV and results in an upper limit of B_h.Γ_ee≤3.00keV(95% C.L.).     

Static properties and semileptonic transitions of lowest-lying double heavy baryons

The static properties and semileptonic decays of ground-state doubly heavy baryons are studied in the framework of a non-relativistic quark model. Using a phenomenological potential model, we calculate the ground-state masses and magnetic moments of doubly heavy Ω and Ξ baryons. In the heavy quark limit, we introduce a simple form of the universal Isgur-Wise function used as the transition form factor and then investigate the exclusive \begin{document}$ b \rightarrow c $\end{document} semileptonic decay widths and branching fractions for \begin{document}$ \dfrac{1}{2}\rightarrow \dfrac{1}{2} $\end{document} baryon transitions. Our obtained results are in agreement with other theoretical predictions.     

Measurement of the absolute branching fraction of D+→K0e+ve via K0→π0π0

By analyzing 2.93 fb^-1 data collected at the center-of-mass energy √s=3.773 GeV with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay D⁺→K⁰e⁺v_e to be B(D⁺→K⁰e⁺v_e)=(8.59±0.14±0.21)% using K⁰→K_S⁰→π⁰π⁰, where the first uncertainty is statistical and the second systematic. Our result is consistent with previous measurements within uncertainties..     

Resolved Photoproduction of J/ψ at HERA

The J/ψ photoproduction via resolved photon process at HERA is studied. It turns out that the J/ψ production is dominated by the leading order production process in low pt range (p_t < 4 GeV), while in the high pt range (p_t > 4 GeV), it is dominated by the fragmentation processes. The difference of J/ψ cross section caused by using GRV and DO photon structure functions is large, especially in the large negative rapidity range. Hence it is possible to use the J/ψ photoproduction process to probe the parton distribution of photon and proton, as well as to test the gluon and heavy quark fragmentation of J/ψ from the perturbative QCD.     

Heavy flavor production at high energyep colliders

The total production rates for heavy quark pairs due to gauge boson fusion processes at high energyep colliders are evaluated. At HERA,b \(\bar t\) production dominates overt \(\bar t\) production form _t ≧60 GeV and is observable up tom _t ?80(90)GeV where the number of expectedb \(\bar t\) events is about 15(10) for ∝L=200pb^?1. Including the contributions fromep→WX→btX the total number of expectedbt events amounts to about 50 events form _t ?80GeV. The influence of thresholds for heavy quark pair production is also studied for the relevant structure functionsF _i (x,Q ²) and shown to contribute to the measured scaling violations. All these effects are sensitive to the heavy quark massesand to the shape of the gluon distribution which can thus be tested experimentally by analyzing heavy quark pair signals.     

Atomic mass,Bjorken variable,and scale dependence of quark transport coefficient in Drell-Yan process for proton incident on nucleus

By means of the nuclear parton distributions determined without the fixed-target Drell-Yan experimental data and the analytic expression of quenching weight based on the BDMPS formalism, next-to-leading order analyses were performed on the Drell-Yan differential cross section ratios from the Fermilab E906 and E866 collaborations. It was found that the results calculated only with the nuclear effects of the parton distribution were not in agreement with the E866 and E906 experimental data. The incoming parton energy loss effect cannot be ignored in the nuclear Drell-Yan reactions. The predicted results indicate that, with the quark transport coefficient as a constant, the suppression due to the target nuclear geometry effect is approximately\begin{document}$ 16.85\ $\end{document}% for the quark transport coefficient. It was shown that we should consider the target nuclear geometry effect in studying the Drell-Yan reaction on nuclear targets. On the basis of the Bjorken variable and scale dependence of the quark transport coefficient, the atomic mass dependence was incorporated. The quark transport coefficient was determined as a function of the atomic mass, Bjorken variable\begin{document}$ x_2 $\end{document}, and scale \begin{document}$ Q^2 $\end{document} by the global fit of the experimental data. The determined constant factor \begin{document}$ \hat{q}_0 $\end{document} of the quark transport coefficient is \begin{document}$ 0.062\pm0.006 $\end{document} GeV\begin{document}$ ^2 $\end{document}/fm. It was found that the atomic mass dependence has a significant impact on the constant factor \begin{document}$ \hat{q}_0 $\end{document} in the quark transport coefficient in cold nuclear matter.     

Quark mass dependence of masses and decay constants of the pseudo-Goldstone bosons in QCD

The dependence of the pseudo-scalar meson masses and decay constants on sea and valence quark masses is compared to next-to-leading order (NLO) chiral perturbation theory (ChPT). The numerical simulations with two light dynamical quark flavors are performed with the Wilson quark lattice action at gauge coupling and hopping parameters on a 16⁴ lattice. lattice artifacts are taken into account by applying chiral perturbation theory for the Wilson lattice action. The values of the relevant combinations of Gasser-Leutwyler constants L ₄, L ₅, L ₆ and L ₈ are estimated.Received: 7 July 2003, Published online: 2 October 2003