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What causes Psi suppression in Pb + Pb Collisions?

Description: A reexamination of hadronic comover scattering indicates that this mechanism cannot explain the observed {psi} suppression in Pb+Pb interactions. The possibility of quark-gluon plasma formation is therefore considered. Implications for RHIC and LHC are also discussed. The agreement of the NA50 Pb+Pb data with naive comover models is reassessed. Previous work is reanalyzed and expanded to include feeding of the {psi}' and {chi}{sub c} states to the {psi}. The effect of color screening is also investigated. Only the {psi}/Drell-Yan (DY) ratios are discussed here.
Date: January 7, 1998
Creator: Vogt, R.
Partner: UNT Libraries Government Documents Department

Possible origin of RHIC R{sub out}/R{sub sid} HBT results

Description: The effects of opacity of the nuclei together with a blackbody type of emission along the system history are considered as a means to explain the ratio R{sub out}=R{sub sid} observed by STAR and PHENIX collaborations at RHIC. Within our model, no flow is required to explain the data trend of this ratio for large surface emissivities.
Date: September 30, 2002
Creator: Padula, Sandra S.
Partner: UNT Libraries Government Documents Department

J/psi Production in Quark-Gluon Plasma

Description: We study J/{psi} production at RHIC and LHC energies with both initial production and regeneration. We solve the coupled set of transport equation for the J/{psi} distribution in phase space and the hydrodynamic equation for evolution of quark-gluon plasma. At RHIC, continuous regeneration is crucial for the J/{psi} momentum distribution while the elliptic flow is still dominated by initial production. At LHC energy, almost all the initially created J/{psi}s are dissociated in the medium and regeneration dominates the J/{psi} properties.
Date: October 30, 2006
Creator: Yan, Li; Zhuang, Pengfei & Xu, Nu
Partner: UNT Libraries Government Documents Department

Correlations and Fluctuations: Status and Perspectives

Description: We will provide an overview of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. Observables, which have been discussed in the literature will be briefly reviewed and put in context with experiment and information from Lattice QCD. Special attention will be given to the QCD critical point and the first order co-existence region.
Date: April 15, 2008
Creator: Koch, Volker & Koch, Volker
Partner: UNT Libraries Government Documents Department


Description: The binding energy of hyper-strange matter in the hadronic phase is calculated as a function of strangeness fraction in the mean field approximation to a relativistic field theory of matter. This is compared to a calculation of Chin and Kerman for the quark phase.
Date: November 1, 1980
Creator: Glendenning, Norman K.
Partner: UNT Libraries Government Documents Department


Description: The major goal of the RHIC experimental program at Brookhaven National Laboratory is to make and study the Quark Gluon Plasma. Another new form of matter, the Color Glass Condensate may be formed in these collisions. The recent results from RHIC are reviewed in this context.
Date: October 2, 2002
Creator: MCLERRAN,L.
Partner: UNT Libraries Government Documents Department

Crystalline structure in the confined-deconfined mixed phase: Neutron stars as an example

Description: We review the differences in first order phase transition of single and multi-component systems, and then discuss the crystalline structure expected to exist in the mixed confined deconfined phase of hadronic matter. The particular context of neutron stars is chosen for illustration. The qualitative results are general and apply for example to the vapor-liquid transition in subsaturated asymmetric nuclear matter.
Date: April 18, 1996
Creator: Glendenning, N.K.
Partner: UNT Libraries Government Documents Department

Parton distributions from SMC and SLAC data

Description: We have extracted spin-weighted parton distributions in a proton from recent data at CERN and SLAC. The valence, sea quark and Antiquark spin-weighted distributions are determined separately. The data are all consistent with a small to moderate polarized gluon distribution, so that the anomaly term is not significant in the determination of the constituent contributions to the spin of the proton. We have analyzed the consistency of the results obtained from various sets of data and the Biorken sum rule. Although all data are consistent with the sum rule, the polarized distributions from different experiments vary, even with higher order QCD corrections taken into account. Results split into two models, one set implying a large polarized strange sea which violates the positivity bound, and the other set yielding a smaller polarized strange sea. Only further experiments which extract information about the polarized sea will reconcile these differences. We suggest specific experiments which can be performed to determine the size of the polarized sea and gluons.
Date: January 4, 1996
Creator: Ramsey, G. P. & Goshtasbpour, M.
Partner: UNT Libraries Government Documents Department

Strange-matter stars

Description: This paper gives an overview of the properties of all possible equilibrium sequences of compact strange-matter stars with nuclear crusts, which range from strange stars to strange dwarfs. In contrast to their non-strange counterparts--neutron stars and white dwarfs--their properties are determined by two (rather than one) parameters, the central star density and the density at the base of the nuclear crust. This leads to stellar strange-matter configurations whose properties are much more complex than those of the conventional sequence. As an example, two generically different categories of stable strange dwarfs are found, which could be the observed white dwarfs. Furthermore the authors find very-low-mass strange stellar objects, with masses as small as those of Jupiter or even lighter planets. Such objects, if abundant enough, should be seen by the presently performed gravitational microlensing searches.
Date: December 5, 1994
Creator: Weber, F.; Kettner, C.; Weigel, M.K. & Glendenning, N.K.
Partner: UNT Libraries Government Documents Department

Sea quark matrix elements and flavor singlet spectroscopy on the lattice

Description: I summarize the results of three recent lattice studies which use stochastic estimator techniques in order to investigate the flavor singlet dynamics in QCD. These include a measurement of the pion-nucleon {sigma}-term, the computation of the flavor singlet axial coupling constant of the nucleon and a determination of flavor singlet meson screening lengths in finite temperature QCD.
Date: December 31, 1996
Creator: Lagae, J.F.
Partner: UNT Libraries Government Documents Department

Gluonic three jet production at next to leading order

Description: I report results from a next-to-leading order event generator of purely gluonic jet production. This calculation, performed in collaboration with Walter Giele, is the first step in the construction of a full next-to-leading order calculation of three jet production at hadron colliders.
Date: August 1, 1996
Creator: Kilgore, W.B.
Partner: UNT Libraries Government Documents Department

Thermal rho`s in the quark-gluon plasma

Description: I discuss different models which predict changes in the mass of the thermal {rho} field. I emphasize that while the predictions are strongly model dependent, nevertheless substantial shifts in the thermal {rho} mass are expected to occur at the point of phase transition. As long as the thermal {rho} peak does not become too broad, this should provide a striking signature of the existence of a phase transition.
Date: March 1, 1995
Creator: Pisarski, R.D.
Partner: UNT Libraries Government Documents Department

Hadron distributions - recent results from the CERN experiment NA44

Description: Proton distributions at midrapidity have been measured for 158A{circ}GeV/c Pb + Pb collisions in the focusing spectrometer experiment NA44 at CERN. A high degree of nuclear stopping is found in the truly heavy ion collisions. Systematic results of single particle transverse momentum distributions of pions, kaons, and protons, of 200A-GeV/c S+S and 158A{circ}GeV/c Pb+Pb central collisions will be addressed within the context of thermalization. By comparing these data with thermal and transport models, freeze-out parameters such as the temperature parameter T{sub fo} and mean collective flow velocity ({Beta}) are extracted. Preliminary results of the particle ratios of K{sup -}/K{sup +} and p/p are discussed in the context of cascade models of RQMD and VENUS.
Date: September 1, 1996
Creator: Xu, N.
Partner: UNT Libraries Government Documents Department

Strangeness production in relativistic nuclear collisions

Description: A review of strange particle production in heavy ion collisions from AGS to SPS energies is presented. Implications of the newest developments in understanding the collision dynamics and the role of strange particle production in the search for a new phase of matter, in both experimental and theoretical sectors, are discussed.
Date: January 1, 1998
Creator: Odyniec, G.J.
Partner: UNT Libraries Government Documents Department

Event by event fluctuations and the QGP

Description: We discuss the physics underlying event-by-event fluctuations in relativistic heavy ion collisions. We will emphasize how the fluctuations of particle ratios can be utilized to explore the properties of the matter created in these collisions. In particular, we will argue that the fluctuations of the ratio of positively over negatively charged particles may serve as a unique signature for the Quark Gluon Plasma.
Date: March 30, 2001
Creator: Koch, V.; Bleicher, M. & Jeon, S.
Partner: UNT Libraries Government Documents Department


Description: A purely hadronic simulation is performed of the recently reported data from PHOBOS at energies of {radical}s = 56, 130 GeV using the relativistic heavy ion cascade LUCIFER which had previously given a good description of the NA49 inclusive spectra at {radical}s = 17.2 GeV/A. The results compare well with these early measurements at RHIC and indeed successfully predict the increase in multiplicity now seen by PHOBOS and the other RHIC detectors at the nominal maximum energy of {radical}s = 200 GeV/A, suggesting that evidence for quark-gluon matter remains elusive.
Date: September 4, 2001
Creator: KAHANA,D.E. & KAHANA,S.H.
Partner: UNT Libraries Government Documents Department

J/{Psi} suppression as an evidence for quark gluon matter

Description: The J/{psi} suppression was originally proposed as a signature of the quark-gluon plasma. Strong suppression of J/{psi} production was indeed observed recently by the NA50 Collaboration at CERN SPS. Is it the first signature of a long-awaited quark-gluon matter, or just a peculiar combination of ''conventional'' effects acting together to produce the puzzling pattern observed experimentally? In this lecture, I am trying to summarize the existing theoretical explanations.
Date: August 10, 1998
Creator: Kharzeev, D.
Partner: UNT Libraries Government Documents Department

Heavy ion physics at the Brookhaven alternating gradient synchrotron

Description: The collision of large nuclei at relativisitic energies is the only known mechanism for creating and studying the properties (equation-of-state, EOS) of extremely dense nuclear matter. At sufficiently high matter densities, one of the most exciting possibilities is the formation of a Quark Gluon Plasma (QGP). However, it is an extremely difficult task to determine the ultimate density achieved during these collisions due to the fleeting nature of the high density state (the lifetime of these states is typically a few times 10-24 ns). We must rely on detailed comparisons between experimental measurements and complex Monte Carlo simulations of the colliding nuclei in order to extract meaningful estimates of the nuclear matter EOS. Our approach has been to study the behavior of the spectator matter (those protons and neutrons which do not directly interact during the collision) to determine the dynamics of the high density state which must necessarily influence the spectator matter as it decays. This report summarizes some of the key results of our study.
Date: January 30, 1995
Creator: Sangster, T.C.
Partner: UNT Libraries Government Documents Department

Measurement of direct photons in 200{center_dot}A GeV {sup 32}S + Au collisions

Description: Two years ago at the 10th Winter Workshop on Nuclear Dynamics, we reported preliminary results from our measurements of photons in reactions of 200{center_dot}A GeV {sup 32}S ions with Au nuclei. The results had been presented earlier at Quark Matter `93. For central collisions we reported a small, but statistically significant, excess of photons over those that can be accounted for by the two-photon decay branches of neutral pions and eta mesons and by the small photon contributions from other radiative decays. This paper is, in a sense, a sequel to the 1994 presentation. Here we present the final WA80 single `direct` photon results, and we discuss their implications for various theoretical calculations. 13 refs., 2 figs., 1 tab.
Date: April 1, 1996
Creator: Plasil, F. & Collaboration, The WA80
Partner: UNT Libraries Government Documents Department