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We study one-particle spectra and a two-particle correlation function in the 130 GeV/nucleon Au+Au collisions at RHIC by making use of a hydrodynamical model. We calculate the one-particle hadronic spectra and present the first analysis of Bose-Einstein correlation functions based on the numerical solution of the hydrodynamical equations which takes both longitudinal and transverse expansion into account appropriately. The hydrodynamical model provides excellent agreement with the experimental data in the pseudorapidity and the transverse momentum spectra of charged hadrons, the rapidity dependence of anti-proton to proton ratio, and almost consistent result for the pion Bose-Einstein correlation functions. Our numerical solution with simple freeze-out picture suggests the formation of the quark-gluon plasma with large volume and low net-baryon density.PACS numbers: 24.10. Nz, 12.38.Mh, 25.75.Gz Relativistic heavy ion collisions are very attracting problems which provide us the nature of hot and dense hadronic matter [1]. Creation of a new state of the matter, the quark-gluon plasma (QGP), and many kinds of new phenomena are expected to be found in the Relativistic Heavy Ion Collider (RHIC) experiments at BNL of which the collision energy is much higher than any other accelerator. However, the complicated processes during the many-body interactions and multiparticle productions are quite hard to catch clear. Therefore, a simple phenomenological description is indispensable for the better understanding of the phenomena. The aims of this paper are, based on a hydrodynamical model, to draw a simple and clear picture of the space-time evolution of the hot and dense matter produced in the high energy heavy ion collisions at RHIC and to give a possible explanation for the recent experimental results.We use a (3+1)-dimensional hydrodynamical model [2] to describe the space-time evolution assuming the local thermal and chemical equilibrium. , where main theme of the analysis is also anisotropic flow. In this paper, we focus our discussion on central collisions by assuming the cylindrical symmetry of the system. We calculate the one-particle hadronic spectra and present the first analysis of Bose-Einstein correlation functions based on the numerical solution of the hydrodynamical equations which takes both longitudinal and transverse expansion into account appropriately [2].The hydrodynamical equations are given as ∂ µ T µν (x) = 0 with the baryon number conservation law ∂ µ n µ B (x) = 0. We numerically solve these coupled equations for the perfect fluid by the method described in Ref. [2]. Our numerical solution keeps entropy, energy and net baryon number conserved within 5% of accuracy throughout the calculation with the time step δτ = 0.01 fm/c. As for an equation of state (EOS), we adopt a bag model EOS in which phase transition of first order takes place [7]. The QGP phase is a free gas with a bag constant B. The gas consists of massless quarks of three flavor and gluons. The hadronic phase is a free resonance g...

We investigate the two-particle intensity correlation function of in relativistic heavy-ion collisions. We find that the behavior of the correlation function at small relative momenta is fairly sensitive to the interaction potential and collective flows. By comparing the results of different source functions and potentials, we explore the effect of intrinsic collective motions on the correlation function. We find that the recent STAR data give a strong constraint on the scattering length and effective range of interaction, as −1.8 fm −1 < 1/a 0 < −0.8 fm −1 and 3.5 fm < r eff < 7 fm, respectively, if samples do not include the feed-down contribution from long-lived particles. We find that the feed-down correction for 0 decay reduces the sensitivity of the correlation function to the detail of the interaction. As a result, we obtain a weaker constraint, 1/a 0 < −0.8 fm −1 . Implication for the signal of existence of H -dibaryon is discussed. Comparison with the scattering parameters obtained from the double hypernucleus may reveal in-medium effects in the interaction.

We investigate possible mass shift and width broadening of J/psi in hot gluonic matter using QCD sum rules. Input values of gluon condensates at finite temperature are extracted from lattice QCD data for the energy density and pressure. Although stability of the moment ratio is achieved only up to T/Tc approximately 1.05, the gluon condensates cause a decrease of the moment ratio, which results in a change of the spectral properties. Using the Breit-Wigner form for the phenomenological side, we find that the mass shift of J/psi just above Tc can reach maximally 200 MeV and the width can broaden to dozens of MeV.

We investigate the medium-induced change of mass and width of J /ψ and η c across the phase transition in hot gluonic matter using QCD sum rules. In the QCD sum rule approach, the medium effect on heavy quarkonia is induced by the change of both scalar and twist-2 gluon condensates, whose temperature dependencies are extracted from the lattice calculations of energy density and pressure. Although the stability of the operator product expansion side seems to break down at T > 1.06T c for the vector channel and T > 1.04T c for the pseudoscalar channel, we find a sudden change of the spectral property across the critical temperature T c , which originates from an equally rapid change of the scalar gluon condensate characterized by ε − 3p. By parametrizing the ground state of the spectral density by the Breit-Wigner form, we find that for both J /ψ and η c , the masses suddenly decrease maximally by a few hundreds of MeV and the widths broaden to ∼100 MeV slightly above T c . The implications for recent and future heavy-ion experiments are discussed. We also carry out a similar analysis for charmonia in nuclear matter, which could serve as a testing ground for observing the precursor phenomena of the QCD phase transition. We finally discuss the possibility of observing the mass shift at nuclear matter at the FAIR project at GSI.

We investigate quarkonium mass spectra in external constant magnetic fields by using QCD sum rules. We first discuss a general framework of QCD sum rules necessary for properly extracting meson spectra from current correlators computed in the presence of strong magnetic fields, that is, a consistent treatment of mixing effects caused in the mesonic degrees of freedom. We then implement operator product expansions for pseudoscalar and vector heavy-quark current correlators by taking into account external constant magnetic fields as operators, and obtain mass shifts of the lowestlying bound states ηc and J/ψ in the static limit with their vanishing spatial momenta. Comparing results from QCD sum rules with those from hadronic effective theories, we find that the dominant origin of mass shifts comes from a mixing between ηc and J/ψ with a longitudinal spin polarization, accompanied by other subdominant effects such as mixing with higher excited states and continua.

We investigate the properties of heavy quarkonia at finite temperature in detail using QCD sum rules. Extending previous analyses, we take into account a temperature dependent effective continuum threshold and derive constraints on the mass, the width, and the varying effective continuum threshold. We find that at least one of these quantities of a charmonium changes abruptly in the vicinity of the phase transition. We also calculate the ratio of the imaginary time correlator to its reconstructed one, G/Grec, by constructing a model spectral function and compare it to the corresponding lattice QCD results. We demonstrate that the almost constant unity of G/Grec can be obtained from the destructive interplay of the changes in each part of the spectral modification which are extracted from QCD sum rules.

We investigate the properties of charmonia in strong magnetic fields by using QCD sum rules. We show how to implement the mixing effects between η(c) and J/ψ on the basis of field-theoretical approaches, and then show that the sum rules are saturated by the mixing effects with phenomenologically determined parameters. Consequently, we find that the mixing effects are the dominant contribution to the mass shifts of the static charmonia in strong magnetic fields.