Energy dependence of resonance production in relativistic heavy ion collisions

The production of the hadronic resonances K^＊0（892）,φ（1020）,∑^＊（1385）,and Ξ^＊（1530） in central AA collisions at √SNN=17.3,200,and 2760 GeV is systematically studied.The direct production of these resonances at system hadronization is described by the quark combination model and the effects of hadron multiple-scattering stage are dealt with by a ultra-relativistic quantum molecular dynamics model（UrQMD）.We study the contribution of these two production sources to final observation and compare the final spectra with the available experimental data.The pT spectra of K^＊0（892） calculated directly by quark combination model are explicitly higher than the data at low pT≤1.5 GeV,and taking into account the modification of rescattering effects,the resulting final spectra well agree with the data at all three collision energies.The rescattering effect on φ（1020） production is weak and including it can slightly improve our description at low p_T on the basis of overall agreement with the data.We also predict the pT spectra of ∑^＊（1385） and Ξ^＊（1530）,to be tested by the future experimental data.

Rapidity and Pseudorapidity Distributions of theVarious Hadron-Species Produced in High EnergyNuclear Collisions: A Systematic Approach

With the help of a phenomenological approach outlined in the text in some detail, we have dealt here with the description of the plots on rapidity and pseudorapidity spectra of some hadron-secondaries produced in various nucleus-nucleus interactions at high energies. The agreement between the measured data and the attempted fits are, on the whole, modestly satisfactory excepting a very narrow central region in the vicinity of y = η = 0. At last, hints to how the steps suggested in the main body of the text to proceed with the description of the measured data given in the plots could lead finally to a somewhat systematic methodology have also been made.

Photon production in relativistic heavy ion collisions with equilibrium and non-equilibrium QGP

We consider the production sources of prompt and thermal photons which include the contribution of gluons in relativistic heavy ion collisions. Considering in our calculation the shadowing and iso-spin effects of the nucleus we can properly estimate the prompt photon production. We develop a new thermal jet-photon conversion mechanism which plays a vital role in the low transverse momentum region. The effect of the non-equilibrium quark-gluon plasma enhances the contribution of thermal photons.

Hadronic rapidity spectra in heavy ion collisions at SPS and AGS energies in a quark combination model

The quark combination mechanism of hadron production is applied to nucleus-nucleus collisions at the CERN Super Proton Synchrotron （SPS） and the BNL Alternating Gradient Synchrotron （AGS）.The rapidity spectra of identified hadrons and their spectrum widths are studied.The data of π -,K±,φ,Λ,Λ,Ξ - and Ξ＋ at 80 and 40 A GeV,and in particular at 30 and 20 A GeV where the onset of deconfinement is suggested to happen,are consistently described by the quark combination model.However,at AGS 11.6 A GeV below the onset,the π±,K±and Λ spectra cannot be simultaneously explained,indicating the disappearance of the intrinsic correlation of their production in the constituent quark level.The collision-energy dependence of the rapidity spectrum widths of the constituent quarks,and the strangeness of the hot and dense quark matter produced in heavy ion collisions,are obtained and discussed.

Different production sources of light nuclei in ultra-relativistic heavy-ion collisions

We systematically study different production sources of light nuclei in ultra-relativistic heavy-ion collisions with a new method, an exclusive quark combination model + an inclusive hadron recombination model. We take deuterons and ~3 He produced in Pb-Pb collisions at ■= 2.76 TeV as examples to show the contribution of different production sources by studying their rapidity densities dN/dy, yield ratios and transverse momentum(PT)spectra just after hadronization and at the final kinetic freeze-out. We find that about a half of d and a fourth of ~3 He created just after hadronization can survive after the hadronic evolution process. Nucleons from A resonance decays make a much larger contribution to the regeneration of light nuclei at the hadronic phase stage, and this contribution is about 77% and 90% for d and ~3 He, respectively, calculated at the final kinetic freeze-out. In addition, we give an explanation for the constant behaviors of yield ratios d/p and ~3 He/p as a function of the averaged charged multiplicity in Pb-Pb collisions and also provide a possible explanation for the observation that d/p in Pb-Pb collisions is larger by a factor of about two than in pp collisions at LHC energies.

Flavor-dependent photoproduction in heavyion collisions

Strong electromagnetic fields produced in the non-central heavy-ion collisions can induce vector meson photoproduction.In this paper,we study the photoproduction J/ψandφmesons in the relativistic heavy-ion collision from ultra-peripheral nuclear collisions to peripheral hadronic heavy ion collisions.And then include both initial hadronic production and thermal production in quark-gluon plasma(QGP).We find,for the charm anti-charm bound state J/ψ,the photoproduced J/ψs are mainly in the very low momentum region and clearly exceed the hadronic production.However,considering the thermal production of strange quark anti-quark pairs in QGP produced in relativistic heavy-ion collisions,the photoproducedφis usually smaller than the thermal production and only evident at very peripheral collisions as even their photoproduction is much larger than J/ψ.

Multiplicity fluctuation and correlation of mesons and baryons in ultra-relativistic heavy-ion collisions at the LHC

We study the multiplicity fluctuation and correlation of identified mesons and baryons formed at hadronization by the quark combination mechanism in the context of ultra-relativistic heavy-ion collisions. Based on the statistical method of free quark combination, we derive the two-hadron multiplicity correlations, including meson-meson and meson-baryon correlations, and take the effects of quark number fluctuation at hadronization into account by a Taylor expansion method. After including the decay contributions, we calculate the dynamical fluctuation observable ν_（dyn） for Kπ, pπ and Kp pairs and discuss what underlying physics can be obtained by comparing with data from Pb-Pb collisions at sNN^（1/2）=2.76 Te V and simulations from the HIJING and AMPT event generators.

Rapidity dependence of hadron p_T spectra in central Au+Au collisions at s_(NN)～(1/2)=200 GeV

The transverse momentum spectra for identified hadrons at different rapidities in central Au＋Au collisions at √^SNN= 200 GeV are studied in a quark combination model. The results for PT spectra of π^±, K^±, p（p^-） and for the p/π ratios in a broader PT range at midrapidity agree well with the data. The transverse momentum spectra of pions, protons and antiprotons at various rapidities y - 1, η= 2.2 and y ≈ 3.2 are calculated and compared with the data.

200GeV下Cu+Cu碰撞中强子产额及其产额比的研究

在夸克组合图像下考虑因子化假设并计入净夸克的影响和强衰变、电磁衰变的贡献,推导出各种末态强子的产额公式.利用产额公式计算RHIC能区Cu+Cu碰撞中质心系能量为200GeV中间快度区不同中心度下的强子产额及产额比,并与实验数据进行比较.通过比较发现,质心系能量为200GeV的Cu+Cu碰撞从中心到边缘的理论计算结果在误差范围内与实验数据符合.

(S_(NN))^(1/2)=130GeV时Au+Au碰撞中的反重子与重子比率

按照夸克随机组合的简单组合模型,本文通过分析得出重子反重子比率与夸克反夸克平均产生几率的关系．进一步计算了相对论重离子碰撞过程中各种反粒子与粒子的比率,不需要任何额外假定, 预言的比率与RHIC加速器时Au+Au碰撞STAR实验的结果基本一致．表明夸克组合模型能够解释相对论重离子碰撞过程的反粒子与粒子比率．