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.
The heavy constituent quark pair of the heavy quarkonium is produced perturbatively and subsequently undergoes hadronization into the bound state non-perturbatively.The production of the heavy quarkonium is essential to testing our understanding of quantum chromodynamics(QCD)in both perturbative and non-perturbative aspects.The electron-positron collider will provide a suitable platform for the precise study of the heavy quarkonium.The higher excited heavy quarkonium may contribute significantly to the ground states,which should be considered for sound estimation.We study the production rates of the higher excited states quarkonium pair in■at the future Z factory under the non-relativistic QCD(NRQCD)framework,where the■represents the color-singlet states■The differential angle distribution of cross sections■is given.We also discuss the uncertainties of cross sections caused by the varying quark masses and the renormalization scaleμ.We show that significant numbers of events for pairs of higher excited state quarkonia can be generated at the super Z factory.
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.
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.
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.
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.
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.
