Hirano Tetsufumi

We investigate the transverse dynamics in Au+Au collisions at √s NN=200 GeV by emphasis upon the interplay between soft and hard components through pT dependences of particle spectra, ratios of yields, suppression factors, and elliptic flow for identified hadrons. From hydrodynamics combined with traversing minijets which go through jet quenching in the hot medium, we calculate interactions of hard jets with the soft hydrodynamic components. It is shown by the explicit dynamical calculations that the hydrodynamic radial flow and the jet quenching of hard jets are the keys to understand the differences among the hadron spectra for pions, kaons, and protons. This leads to the natural interpretation for Np/N π ∼ 1, RAA ≳ 1 for protons, and v 2p&gt v2π recently observed in the intermediate transverse momentum region at Relativistic Heavy Ion Collider.

We calculate the one-particle hadronic spectra and correlation functions of pions based on a hydrodynamical model. Parameters in the model are so chosen that the one-particle spectra reproduce experimental results of √s = 130 A·GeV Au + Au collisions at RHIC. Based on the numerical solution, we discuss the space-time evolution of the fluid. Two-pion correlation functions are also discussed. Our numerical solution suggests the formation of the quark-gluon plasma with large volume and low net baryon density.

We investigate the suppression factor and the azimuthal correlation function for high PT hadrons in central Au+Au collisions at roots(NN) = 200 GeV by using a dynamical model in which hydrodynamics is combined with explicitly traversing jets. We study the effects of parton energy loss in a hot medium, intrinsic k(T) of partons in a nucleus, and p(perpendicular to) broadening of jets on the back-to-back correlations of high p(T) hadrons. All these effects are found to be responsible for the disappearance of the away-side peaks in correlation functions.

Based on a hydrodynamical model, we compare 130 GeV/nucleon Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and 17 GeV/nucleon Pb+Pb collisions at the Super Proton Synchrotron (SPS). The model well reproduces the single-particle distributions of both the RHIC and SPS. The numerical solution indicates that a huge amount of collision energy in the RHIC is mainly used to produce a large extent of hot fluid rather than to make a high temperature matter the longitudinal extent of the hot fluid in the RHIC is much larger than that of the SPS and the initial energy density of the fluid is only 5% higher than the one in the SPS. The solution well describes the HBT radii at the SPS energy but shows some deviations from the ones at the RHIC.

Based on a hydrodynamical model, we compare 130 GeV/nucleon Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and 17 GeV/nucleon Pb+Pb collisions at the Super Proton Synchrotron (SPS). The model well reproduces the single-particle distributions of both the RHIC and SPS. The numerical solution indicates that a huge amount of collision energy in the RHIC is mainly used to produce a large extent of hot fluid rather than to make a high temperature matter; the longitudinal extent of the hot fluid in the RHIC is much larger than that of the SPS and the initial energy density of the fluid is only 5% higher than the one in the SPS. The solution well describes the HBT radii at the SPS energy but shows some deviations from the ones at the RHIC.

We study one-particle spectra and a two-particle correlation function in the 130 GeV/nucleon Au+Au collisions at the Relativistic Heavy Ion Collider by making use of a hydrodynamical model. We calculate the one-particle hadronic spectra and present an analysis of Bose-Einstein correlation functions based on a 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 the antiproton-to-proton ratio, and almost consistent results for the pion Bose-Einstein correlation functions. Our numerical solution with a simple freeze-out picture suggests the formation of a quark-gluon Plasma With large volume and low net-baryon density.