z-scaling in heavy ion collisions at the RHIC

Experimental data on transverse particle spectra obtained by the STAR, PHENIX, PHOBOS, and BRAHMS collaborations at the RHIC are analyzed in the framework of the generalized concept of z-scaling. It was developed for analysis of inclusive particle production in proton-(anti)proton collisions at high p _T and high multiplicities. The general scheme of the approach based on the physical principles of self-similarity, locality, and fractality is reviewed. Independence of the scaling function ψ(z) from energy, multiplicity, and atomic weight for h ^±, π ^±,0, K _S ⁰ , and Λ hadrons produced in Au-Au and Cu-Cu collisions at √s = 130 and 200 GeV is discussed. Based on z-scaling, the multiplicity dependence of pion transverse spectra up to p _T = 25 GeV/c in Au-Au collisions at √s = 200 GeV for experiments at the RHIC is predicted. The text was submitted by the author in English.     

Partonic effects in heavy ion collisions at RHIC

Effects of partonic interactions in heavy ion collisions at RHIC are studied in a multiphase transport model (AMPT) that includes both initial partonic and final hadronic interactions. It is found that a large parton scattering cross section is needed to understand the measured elliptic flow of pions and two-pion correlation function.     

Probing the QCD chiral cross-over transition in heavy ion collisions

We argue that by measuring higher moments of the net proton number fluctuations in heavy ion collisions (HIC) one can probe the QCD chiral cross-over transition experimentally. We discuss the properties of fluctuations of the net baryon number in the vicinity of the chiral cross-over transition within the Polyakov loop extended quark-meson model at finite temperature and baryon density. The calculation includes non-perturbative dynamics implemented within the functional renormalization group approach. We find a clear signal for the chiral cross-over transition in the fluctuations of the net baryon number. We address our theoretical findings to experimental data of the STAR Collaboration on energy and centrality dependence of the net proton number fluctuations and their probability distributions in HIC.     

Photon-photon luminosities in relativistic heavy ion collisions at LHC energies

Effective – luminosities are calculated for various realistic hadron collider scenarios. The main characteristics of photon-photon processes at relativistic heavy-ion colliders are established and compared to the corresponding –-luminosities ate ⁺-e ^– — and future photon linear colliders (PLC). Higher order corrections as well as inelastic processes are discussed. It is concluded that feasible high luminosity Ca–Ca collisions at the Large Hadron Collider (LHC) are an interesting option for – physics up to about 100 GeV – CM energy.     

Novel jet quenching observables in heavy ion collisions at the LHC

We discuss such novel jet quenching observables at the LHC as direct measurements of medium-modified jet fragmentation function, nuclear modification factor and azimuthal anisotropy for jets with finite cone size and p _T -imbalance for dimuon tagged jets. The corresponding predictions obtained with PYQUEN partonic energy loss model are presented.     

Open heavy flavor production from light ion collisions at RHIC

PHENIX measures leptons at mid and forward rapidities and extracts leptons resulting from semi-leptonic decays of heavy quarks. We present PHENIX results related to heavy quark production, specifically the invariant cross section of the non-photonic single electrons produced at midrapidity in p+p and d+Au collisions at $\sqrt {s_{NN} } = 200$ GeV. The measured cross section for p+p collisions is compared with the NLO prediction, and a possible excess over the prediction is noted. The measured cross section for d+Au collisions scales with the number of colliding nucleon pairs from the p+p spectra.     

Radion and Higgs signals in peripheral heavy ion collisions at the LHC

We investigate the sensitivity of the heavy ion mode of the LHC to Higgs boson and Radion production via photon–photon fusion through the analysis of the processes γγ→γγ, , and γγ→gg in peripheral heavy ion collisions. We suggest cuts to improve the Higgs and Radion signal over standard model background ratio and determine the capability of LHC to detect these particles production.     

Probing the QCD phase boundary with elliptic flow in relativistic heavy ion collisions at STAR

We present measurement of elliptic flow, v ₂, for charged and identified particles at midrapidity in Au+Au collisions at $\sqrt {s_{NN} } $ = 7.7?C39 GeV. We compare the inclusive charged hadron v ₂ to those from transport model calculations, such as the UrQMD model, AMPT default model and AMPT string-melting model. We discuss the energy dependence of the difference in v ₂ between particles and anti-particles. The v ₂ of ? meson is observed to be systematically lower than other particles in Au+Au collisions at $\sqrt {s_{NN} } $ = 11.5 GeV.     

Size of the freeze-out source in high energy heavy ion collisions

Based on a hydro-inspired azimuthally symmetric emission function, we analyze the HBT radius R_s and the single-particle transverse momentum spectra in Au+Au collisions measured by the STAR Collaboration at √s_NN=200 GeV. The results show that consistent assumptions about transverse density (and/or flow profile) in the calculation of the HBT radius R_s and single-particle spectral analyses play an important role for understanding the size of the freeze-out source.     

Size of the freeze-out source in high energy heavy ion collisions

Based on a hydro-inspired azimuthally symmetric emission function, we analyze the HBT radius Rs and the single-particle transverse momentum spectra in Au+Au collisions measured by the STAR Collaboration at SNN = 200 GeV. The results show that consistent assumptions about transverse density (and/or flow profile) in the calculation of the HBT radius Rs and single-particle spectral analyses play an important role for understanding the size of the freeze-out source.     

From chemical freeze-out to critical conditions in heavy ion collisions

We compare the statistical thermodynamics of hadron resonance gas with recent LGT results at finite chemical potential. We argue that for T≤T _cthe equation of state derived from Monte-Carlo simulations of 2-quark-flavor QCD at finite chemical potential is consistent with that of a hadron resonance gas when applying the same set of approximations as used in LGT calculations. We indicate the relation of chemical freeze-out conditions obtained from a detailed analysis of particle production in heavy ion collisions with the critical conditions required for deconfinement. We argue that the position of a hadron quark-gluon boundary line in temperature chemical potential plane can be determined in terms of the resonance gas model by the condition of fixed energy density.     

Thermal parameters in heavy ion collisions at SPS and RHIC: Centrality dependence

The centrality dependence of thermal parameters describing hadron multiplicities and intermediate-mass dilepton spectra in heavy ion collisions at SPS and RHIC is analyzed. From experimental hadron multiplicities we deduce evidence for strangeness saturation at high energy and maximum centrality. The observed dilepton spectra can be parameterized by a centrality independent temperature.     

Centrality dependence of pseudorapidity distributions of baryons in heavy ion collisions at RHIC

The energy and centrality independence of the limiting fragmentation for produced mesons have been used to extract the reduced pseudorapidity (η′ = η − η _beam ) distributions of charged baryons at forward rapidity. The distribution crosses at η′ ≈ = −1 suggesting the prominence of beam protons above that rapidity. The loss of beam rapidity has been extracted which has been found to increase with centrality.     

Chiral QCD phase transition in nuclear collisions

The characteristic aspects of multiparticle states generated at , as a result of chiral QCD phase transition, are studied in the framework of the O(4) theory. Predictions concerning critical events, in connection with current and future experiments with ultrarelativistic heavy ions, are presented. Received: 9 June 1997 / Revised version: 18 July 1997 / Published online: 26 February 1998     

Open and hidden charm production in dA collisions at RHIC and LHC

We discuss aspects of open and hidden charm production in deuterium-nucleus collisions at RHIC and LHC energies. We describe calculations of the total cross section and the charm quark transverse momentum distributions. We next explain how shadowing and moderate nuclear absorption can explain the PHENIX d Au/pp ratios and predict the combined effect of shadowing and absorption in 6.2 TeV d + Pb collisions.Arrival of the final proofs: 28 April 2005     

VISHNU hybrid model for the viscous QCD matter at RHIC and LHC energies

In this proceeding, we briefly describe the viscous hydrodynamics + hadron cascade hybrid model VISHNU for relativistic heavy ion collisions and report the current status on extracting the QGP viscosity from elliptic flow data.