1,114 research outputs found
Towards the 3D-Imaging of Sources
Geometric details of a nuclear reaction zone, at the time of particle
emission, can be restored from low relative-velocity particle-correlations,
following imaging. Some of the source details get erased and are a potential
cause of problems in the imaging, in the form of instabilities. These can be
coped with by following the method of discretized optimization for the restored
sources. So far it has been possible to produce 1-dimensional emission source
images, corresponding to the reactions averaged over all possible spatial
directions. Currently, efforts are in progress to restore angular details.Comment: Talk given at the Int. Workshop on Hot and Dense Matter in
Relativistic Heavy Ion Collisions, March 24-27, 2004, Budapest; 10 pages, 6
figure
Constraining the initial temperature and shear viscosity in a hybrid hydrodynamic model of =200 GeV Au+Au collisions using pion spectra, elliptic flow, and femtoscopic radii
A new framework for evaluating hydrodynamic models of relativistic heavy ion
collisions has been developed. This framework, a Comprehesive Heavy Ion Model
Evaluation and Reporting Algorithm (CHIMERA) has been implemented by augmenting
UVH 2+1D viscous hydrodynamic model with eccentricity fluctuations,
pre-equilibrium flow, and the Ultra-relativistic Quantum Molecular Dynamic
(UrQMD) hadronic cascade. A range of initial temperatures and shear viscosity
to entropy ratios were evaluated for four initial profiles, and
scaling with and without pre-equilibrium flow. The model results
were compared to pion spectra, elliptic flow, and femtoscopic radii from 200
GeV Au+Au collisions for the 0--20% centrality range.Two sets of initial
density profiles, scaling with pre-equilibrium flow and
scaling without were shown to provide a consistent description of all three
measurements.Comment: 21 pages, 32 figures, version 3 includes additional text for
clarification, division of figures into more manageable units, and placement
of chi-squared values in tables for ease of viewin
Imaging Three Dimensional Two-particle Correlations for Heavy-Ion Reaction Studies
We report an extension of the source imaging method for analyzing
three-dimensional sources from three-dimensional correlations. Our technique
consists of expanding the correlation data and the underlying source function
in spherical harmonics and inverting the resulting system of one-dimensional
integral equations. With this strategy, we can image the source function
quickly, even with the finely binned data sets common in three-dimensional
analyses.Comment: 13 pages, 11 figures, submitted to Physical Review
Search for a Signal on QCD Critical Point in Central Nucleus-Nucleus Collisions
We discuss that the QCD critical point could appear in central collisions in
percolation cluster. We suggest using the nuclear transparency effect and the
one of the light nuclear production to identify the critical point.Comment: To appear in the proceedings of the 20th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions (QM2008), Jaipur, India,
February 4-10, 200
Fluctuations and Correlations of net baryon number, electric charge, and strangeness: A comparison of lattice QCD results with the hadron resonance gas model
We calculate the quadratic fluctuations of net baryon number, electric charge
and strangeness as well as correlations among these conserved charges in
(2+1)-flavor lattice QCD at zero chemical potential. Results are obtained using
calculations with tree level improved gauge and the highly improved staggered
quark (HISQ) actions with almost physical light and strange quark masses at
three different values of the lattice cut-off. Our choice of parameters
corresponds to a value of 160 MeV for the lightest pseudo scalar Goldstone mass
and a physical value of the kaon mass. The three diagonal charge
susceptibilities and the correlations among conserved charges have been
extrapolated to the continuum limit in the temperature interval 150 MeV <T <
250 MeV. We compare our results with the hadron resonance gas (HRG) model
calculations and find agreement with HRG model results only for temperatures
T<= 150 MeV. We observe significant deviations in the temperature range 160 MeV
< T < 170 MeV and qualitative differences in the behavior of the three
conserved charge sectors. At T < 160 MeV quadratic net baryon number
fluctuations in QCD agree with HRG model calculations while, the net electric
charge fluctuations in QCD are about 10% smaller and net strangeness
fluctuations are about 20% larger. These findings are relevant to the
discussion of freeze-out conditions in relativistic heavy ion collisions.Comment: 17 pages, 18 EPS-files, 5 tables, revised version includes continuum
limit extrapolations of off-diagonal susceptibilities, to appear in Phys.
Rev.
Equation of state and QCD transition at finite temperature
We calculate the equation of state in 2+1 flavor QCD at finite temperature
with physical strange quark mass and almost physical light quark masses using
lattices with temporal extent Nt=8. Calculations have been performed with two
different improved staggered fermion actions, the asqtad and p4 actions.
Overall, we find good agreement between results obtained with these two O(a^2)
improved staggered fermion discretization schemes. A comparison with earlier
calculations on coarser lattices is performed to quantify systematic errors in
current studies of the equation of state. We also present results for
observables that are sensitive to deconfining and chiral aspects of the QCD
transition on Nt=6 and 8 lattices. We find that deconfinement and chiral
symmetry restoration happen in the same narrow temperature interval. In an
Appendix we present a simple parametrization of the equation of state that can
easily be used in hydrodynamic model calculations. In this parametrization we
also incorporated an estimate of current uncertainties in the lattice
calculations which arise from cutoff and quark mass effects. We estimate these
systematic effects to be about 10 MeVComment: 31 pages, 24 EPS-figure
Recommended from our members
Energy Lossand Flow of Heavy Quarks in Au+Au Collisions at root-s=200GeV
The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3 < p{sub rmT} < 9 GeV/c at midrapidity (|y| < 0.35) from heavy flavor (charm and bottom) decays in Au+Au collisions at {radical}s{sub NN} = 200 GeV. The nuclear modification factor R{sub AA} relative to p+p collisions shows a strong suppression in central Au+Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy, v{sub 2}, with respect to the reaction plane is observed for 0.5 < p{sub rmT} < 5 GeV/c indicating non-zero heavy flavor elliptic flow. A simultaneous description of R{sub AA}(p{sub rmT}) and v{sub 2}(p{sub rmT}) constrains the existing models of heavy-quark rescattering in strongly interacting matter and provides information on the transport properties of the produced medium. In particular, a viscosity to entropy density ratio close to the conjectured quantum lower bound, i.e. near a perfect fluid, is suggested
The Interpersonal Style and Complementarity Between Crisis Negotiators and Forensic Inpatients
Previous negotiation research has explored the interaction and communication between crisis negotiators and perpetrators. A crisis negotiator attempts to resolve a critical incident through negotiation with an individual, or group of persons in crisis. The purpose of this study was to establish the interpersonal style of crisis negotiators and complementarity of the interpersonal interaction between them and forensic inpatients. Crisis negotiators, clinical workers and students (n = 90) used the Check List of Interpersonal Transactions-Revised (CLOIT-R) to identify interpersonal style, along with eight vignettes detailing interpersonal styles. Crisis negotiators were most likely to have a friendly interpersonal style compared to the other non-trained groups. Complementarity theory was not exclusively supported as submissive individuals did not show optimistic judgments in working with dominant forensic inpatients and vice versa. Exploratory analysis revealed that dominant crisis negotiators were optimistic in working with forensic inpatients with a dominant interpersonal style. This study provides insight into the area of interpersonal complementarity of crisis negotiators and forensic inpatients. Whilst further research is required, a potential new finding was established, with significant ‘similarity’ found when dominant crisis negotiators are asked to work with dominant forensic inpatients
Antiproton Production in Collisions at AGS Energies
Inclusive and semi-inclusive measurements are presented for antiproton
() production in proton-nucleus collisions at the AGS. The inclusive
yields per event increase strongly with increasing beam energy and decrease
slightly with increasing target mass. The yield in 17.5 GeV/c p+Au
collisions decreases with grey track multiplicity, , for ,
consistent with annihilation within the target nucleus. The relationship
between and the number of scatterings of the proton in the nucleus is
used to estimate the annihilation cross section in the nuclear
medium. The resulting cross section is at least a factor of five smaller than
the free annihilation cross section when assuming a small or
negligible formation time. Only with a long formation time can the data be
described with the free annihilation cross section.Comment: 8 pages, 6 figure
- …