An experimental review of open heavy flavor and quarkonium production at RHIC

Open heavy flavors and quarkonia are unique probes of the hot–dense medium produced in heavy-ion collisions. Their production in p+p collisions also constitutes an important test of QCD. In this paper, we review selected results on the open heavy flavors and quarkonia generated in the p+p and heavy-ion collisions at the Relativistic Heavy Ion Collider. The physical implications are also discussed.

Thermal Width for Heavy Quarkonium in the Static Limit

The thermal widths for heavy quarkonia are calculated for both Coulomb gauge （CG） and Feynman gauge （FG）, and the comparisons between these results with the hard thermal loop （HTL） approximation ones are illustrated. The dissociation temperatures of heavy quarkonia in thermal medium are also discussed for CG, FG and HTL cases. It is shown that the thermal widths, derived from the HTL approximation and used in many research studies, cause some errors in the practical calculations at the temperature range accessible in the present experiment, and the problem of gauge dependence cannot be avoided when the complete self energy is used in the derivation of potential.

1-16 Glueball Quarkonium Mixing in QCD

Despite of the fact that the quark model has been very successful in describing hadron spectrum, there are still some exotic states cannot be explained well. Glueball is one of the most interesting issue among the exotic states.The general wisdom is that QCD must have the glueballs made of gluons. And there are many models have been proposed to describe the physics of glueball[1?5].

Light quarkonium and charmonium mass shifts in an unquenched quark model

The unquenched quark model for the light quarkonium and charmonium states is explored in this study.The quark-pair creation operator in the^(3)P_(0) model,which combines the two-quark and four-quark components,is modified by considering the effects of the created quark pair's energy.Furthermore,the separation between the created quark pair and valence quark pair is modified.All the wave functions,including those for the mesons and the relative motion between two mesons,are obtained by solving the corresponding Schrodinger equation using the Gaussian expansion method.The aim of this study is to find a new set of parameters that can accurately describe the mass spectrum of low-lying light quarkonium and charmonium states.Moreover,certain exotic states,such as X(3872),can be described well in the unquenched quark model.

Production of a heavy quarkonium with a photon or via ISR at Z peak in e^+e^- collider

Considering the possibility to build an e + e-collider at the energies around Z-boson resonance with a luminosity so high as L ∝ 10 34 cm-2 s-1 (even higher) and the abilities of a modern synthesis detector,we systematically calculate the exclusive two body processes of the heavy quarkonium production: e + eannihilates into a heavy quarkonium and a photon,involving the initial state radiation (i.e.ISR) cases,at the energies around the Z-boson resonance.Since the couplings of Z-boson to quarks contain an axial vector term as well as a vector one,a charmonium such as J/ψ or η c or h c or χ cJ ···,or a bottomonium such as Υ or η b or h b or χ bJ ···,associating with a photon,may be produced respectively via Z-boson annihilation.If we call such a collider with so high luminosity and running around the Z-boson resonance as a Z-factory,then our results obtained here indicate that experimental studies of the various heavy quarkona (their ground and excited states) via the two-body processes at a Z-factory have outstanding advantages,especially,the production of the possible states with quantum numbers J PC = 1-via ISR.

Relativistic correction to gluon fragmentation function into pseudoscalar quarkonium

Inspired by the recent measurements of the ηc meson production at LHC experiments, we investigate the relativistic correction effect for the fragmentation functions of gluon/charm quark fragmenting into ηc, which constitute the crucial nonperturbative element for the ηc production at high pT. Employing three distinct methods,we calculate the next-to-leading-order（NLO） relativistic correction to g →ηc fragmentation function in the NRQCD factorization framework, as well as verifying the existing NLO result for the c →ηc fragmentation function. We also study the evolution behavior of these fragmentation functions with the aid of the DGLAP equation.

Melting temperature of heavy quarkonium with a holographic potential up to sub-leading order

A calculation of the melting temperatures of heavy quarkonium states with the holographic potential was introduced in a previous work. In this paper, we consider the holographic potential at sub-leading order, which permits finite coupling corrections to be taken into account. It is found that this correction lowers the dissociation temperatures of heavy quarkonium.

Next-to-leading order QCD corrections to Higgs boson decay to quarkonium plus a photon

In this paper, we investigate the decay of the Higgs boson to J/ψ（γ ） plus a photon based on NRQCD factorization. For the direct process, we calculate the decay width up to QCD NLO. We find that the decay width for process H → J/ψ（γ ） ＋γ direct production at the LO is significantly reduced by the NLO QCD corrections. For the indirect process, we calculate the H→γ＊γ, with virtual 7 substantially decaying to J/ψ（γ）, including all the SM Feynman diagrams. The decay width of indirect production is much larger than the direct decay width. Since it is very clean in experiment, the H →J/ψ（ γ） ＋γ decay could be observable at a 14 TeV LHC and it also offers a new way to probe the Yukawa coupling and New Physics at the LHC.

Calculation of dissociation temperature of quarkonium using Gaussian Expansion Method

The dissociation temperatures of quarkonium states in a thermal medium are obtained in the framework of the quark model with the help of the Gaussian Expansion Method（GEM）.This is the first time this method has been applied to the dissociation problem of mesons.The temperature-dependent potential is obtained by fitting the lattice results.Solving the Schr¨odinger equation with the GEM,the binding energies and corresponding wave functions of the ground states and the excited states are obtained at the same time.The accuracy and efficiency of the GEM provide a great advantage for the dissociation problem of mesons.The results show that the ground states1^1S（0 ）and 1^3S（1 ）have much higher dissociation temperatures than other states,and the spin-dependent interaction has a significant effect on the dissociation temperatures of 1^3S（1 ）and 1^1S0.We also suggest using the radius of the bound state as a criterion of quarkonium dissociation.This can help to avoid the inaccuracy caused by the long tail of quarkonium binding energy dependence on temperature.

Theory for quarkonium:from NRQCD factorization to soft gluon factorization

We demonstrate that the recently proposed soft gluon factorization(SGF)is equivalent to the nonrelativistic QCD(NRQCD)factorization for heavy quarkonium production or decay,which means that,for any given process,these two factorization theories are either both valid or both violated.We use two methods to arrive at this conclusion.In the first method,we apply the two factorization theories to the physical process J/ψ→e^+e^-.Our explicit calculation shows that both SGF and NRQCD can correctly reproduce the low energy physics of full QCD,and the two factorizations are thus equivalent.In the second method,by using equations of motion,we successfully deduce SGF from NRQCD effective field theory.By identifying SGF with NRQCD factorization,we establish relations between the two factorization theories and prove the generalized Gremm-Kapustin relation as a byproduct.Compared with the NRQCD factorization,the advantage of SGF is that it resums the series of relativistic corrections originating from kinematic effects to all powers,yielding better convergence of the relativistic expansion.

Entropic destruction of heavy quarkonium with hyperscaling violation

We study the entropic destruction of heavy quarkonium in strongly coupled theories with an anisotropic scaling symmetry in time and a spatial direction.We consider Lifshitz and hyperscaling violation theories,which are covariant under a generalized Lifshitz scaling symmetry with the dynamical exponent z and hyperscaling violation exponentθ.It is shown that the entropic force depends on the parameters of these theories.In particular,increasing z decreases the entropic force,thus reducing the quarkonium dissociation,while increasingθhas the opposite effect.

Entropic destruction of heavy quarkonium in a rotating hot and dense medium from holography

Previous studies have indicated that the peak of the quarkonium entropy at the deconfinement transition can be related to the entropic force,which would induce the dissociation of heavy quarkonium.In this study,we investigated the entropic force in a rotating hot and dense medium using AdS/CFT correspondence.It was found that the inclusion of angular velocity increases the entropic force,thus enhancing quarkonium dissociation,while chemical potential has the same effect.The results imply that the quarkonium dissociates easier in rotating medium compared with the static case.

Revisiting the heavy vector quarkonium leptonic widths

We revisit the heavy quarkonium leptonic decays ψ(nS)→■^+■^- and Υ(nS)→■^+■^- using the Bethe-Salpeter method.The emphasis is on the relativistic corrections.For the ψ(1S-5S)decays,the relativistic effects are 22-2^+3%,34-2^+5%,41-6^+6%,52-13^+11% and 62-12^+14%,respectively.For the Υ(1S-5S) decays,the relativistic effects are 14-2^+1%,23-3^+0%,20-2^+8%,21-7^+6% and 28-7^+2%,respectively.Thus,the relativistic corrections are large and important in heavy quarkonium leptonic decays,especially for the highly excited charmonium.Our results forΥ(nS)→■^+■^- are consistent with the experimental data.

Novel quantum phenomena induced by strong magnetic fields in heavy-ion collisions

The relativistic heavy-ion collisions create both hot quark–gluon matter and strong magnetic fields, and provide an arena to study the interplay between quantum chromodynamics and quantum electrodynamics. In recent years, it has been shown that such an interplay can generate a number of interesting quantum phenomena in hadronic and quark–gluon matter. In this short review, we first discuss some properties of the magnetic fields in heavy-ion collisions and then give an overview of the magnetic fieldinduced novel quantum effects. In particular, we focus on the magnetic effect on the heavy flavor mesons, the heavyquark transports, and the phenomena closely related to chiral anomaly.

Cornell势下薛定谔方程本征值问题的代数解法

提出了求解球对称势作用下薛定谔方程的无穷级数代数解法;应用所提出的方法求出了库仑势和线性势的能量本征值;对Cornell势还计算了殊粲夸克偶偶素(J/Ψ)家族和底夸克偶素(γ)的质量谱,其理论结果与实验数据符合较好.

Anisotropy flows in Pb-Pb collisions at LHC energies from parton scatterings with heavy quark trigger

By implementing an additional heavy quark-antiquark pair production trigger in a multiphase transport(AMPT)model,we study the effect on anisotropy flows of identified particles with a focus on charged particles and quarkonium(J/ΨandΥ).A systematic increase in the collision rate for active partons in the AMPT model with such an implementation has been observed.It leads to a slight increase of identified particles anisotropy flows as a function of transverse momentum(pT)and rapidity,and gives a better description of the experimental data of elliptic flow toward larger pT.Our approach provides an efficient way to study the heavy quark dynamics in the AMPT model at LHC energies.

重夸克偶素质量谱的超精细辟裂

给出了Cornell势到v2/c2级次的所有相对论修正和湮没修正.计算了重夸克偶素的质量谱,并与实验数据符合较好.系统地讨论了湮没项和v2/c2级次的相对论修正项对能谱分裂的作用.

重夸克偶素质量谱的数值计算

本文采用一种简单的相对论势模型来计算重夸克偶素的质量谱。由于除S态外描述夸克偶素的波动方程无严格解,故我们对此进行差分并利用计算机求出了重夸克偶素任意状态的质量谱。

色八重态对协同J/ψ+γ产生过程的影响

利用双重 Q2 -重标度模型给出的胶子分布函数计算并讨论了重夸克偶素的色八重态对协同 J/ψ+ γ产生过程的影响 .结果表明 :色八重态的贡献不可以忽略 ,有时能超过色单态的贡献 .所得计算结果与未来实验数据的比较 ,可以对双重 Q2 -重标度模型进行检验 .

χ_c粒子轻强子及双光子衰变过程中长程矩阵元的研究

在NRQCD因子化框架下,通过χ_(c0)与χ_(c2)衰变过程对χ_c的长程矩阵元进行了研究.结果表明,相对论修正与领头阶矩阵元的大小关系满足NRQCD速度标度律.