502 Matching Results

Search Results

Advanced search parameters have been applied.

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

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

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


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

Strangeness at SIS energies

Description: In this contribution the authors discuss the physics of strange hadrons in low energy ({approx_equal} 1-2 AGeV) heavy ion collision. In this energy range the relevant strange particle are the kaons and anti-kaons. The most interesting aspect concerning these particles are so called in-medium modifications. They will attempt to review the current status of understanding of these in medium modifications. In addition they briefly discuss other issues related with kaon production, such as the nuclear equation of state and chemical equilibrium.
Date: September 28, 2005
Creator: Koch, Volker
Partner: UNT Libraries Government Documents Department


Description: Two decades ago Matsui and Satz suggested that Debye screening in the quark-gluon plasma would result in J/{psi} suppression in heavy ion collisions. Much has happened in the subsequent years, and the picture of quark-gluon plasma at present is rapidly evolving - what does it imply for the J/{psi} suppression? What are the recent RHIC and SPS results trying to tell us? What else has to be done? This talk is an attempt to address these questions.
Date: November 14, 2006
Creator: KHARZEEV,D.
Partner: UNT Libraries Government Documents Department

HEND: A Database for High Energy Nuclear Data

Description: We propose to develop a high-energy heavy-ion experimental database and make it accessible to the scientific community through an on-line interface. The database will be searchable and cross-indexed with relevant publications, including published detector descriptions. It should eventually contain all published data from older heavy-ion programs such as the Bevalac, AGS, SPS and FNAL fixed-target programs, as well as published data from current programs at RHIC and new facilities at GSI (FAIR), KEK/Tsukuba and the LHC collider. This data includes all proton-proton, proton-nucleus to nucleus-nucleus collisions as well as other relevant systems and all measured observables. Such a database would have tremendous scientific payoff as it makes systematic studies easier and allows simpler benchmarking of theoretical models to a broad range of experiments. To enhance the utility of the database, we propose periodic data evaluations and topical reviews. These reviews would provide an alternative and impartial mechanism to resolve discrepancies between published data from rival experiments and between theory and experiment. Since this database will be a community resource, it requires the high-energy nuclear physics community's financial and manpower support.
Date: February 21, 2007
Creator: Brown, D & Vogt, R
Partner: UNT Libraries Government Documents Department

Charmonium production in P-A collisions.

Description: A review of J / {psi} and {psi}' production (charmonium) in proton-nucleus collisions is given including results from measurements at fixed target experiments at both Fermilab (E866/NuSea) and CERN (NA50) and some discussion of planned measurements at RHIC and NA60. The important physics that contributes to the large suppression in production of charmonium will be discussed as will be information from complementary measurements of open-charm production, and the Drell-Yan process. The differences in the results from Fermilab and CERN and the evolution of this physics to RHIC energies will be shown. The importance of a clear understanding of these effects in order to use J / {psi} suppression as a tool for study of the Quark-gluon plasma in nucleus-nucleus collisions at RHIC will be highlighted.
Date: January 1, 2001
Creator: Leitch, M. J.
Partner: UNT Libraries Government Documents Department


Description: We introduce a generalized definition of parton distribution functions (PDFs) for a more consistent all-order treatment of power corrections. We present a new set of modified DGLAP evolution equations for nuclear PDFs, and show that the resummed {alpha}{sub s}A{sup 1/3}/Q{sup 2}-type of leading nuclear size enhanced power corrections significantly slow down the growth of gluon density at small-x. We discuss the relation between the calculated power corrections and the saturation phenomena.
Date: November 14, 2006
Creator: QIU, J.-W.
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