1,165 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
Exploring Lifetime Effects in Femtoscopy
We investigate the role of lifetime effects from resonances and emission
duration tails in femtoscopy at RHIC in two Blast-Wave models. We find the
non-Gaussian components compare well with published source imaged data, but the
value of R_out obtained from Gaussian fits is not insensitive to the
non-Gaussian contributions when realistic acceptance cuts are applied to
models.Comment: 5 pages, 2 figure
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Ferrenberg Swendsen Analysis of LLNL and NYBlue BG/L p4rhms Data
These results are from the continuing Lattice Quantum Chromodynamics runs on BG/L. These results are from the Ferrenberg-Swendsen analysis [?] of the combined data from LLNL and NYBlue BG/L runs for 32{sup 3} x 8 runs with the p4rhmc v2.0 QMP-MPI.X (semi-optimized p4 code using qmp over mpi). The jobs include beta values ranging from 3.525 to 3.535 with an alternate analysis extending to 3.540. The NYBlue data sets are from 9k trajectories from Oct 2007, and the LLNL data are from two independent streams of {approx}5k each, taking from the July 2007 runs. The following outputs are produced by the fs-2+1-chiub.c program. All outputs have had checksums produced by addCks.pl and checked by the checkCks.pl perl script after scanning
Kaon and production vs Participants in Nuclear Collisions
Data on kaon and production in nuclear collisions as a function of
centrality are analysed both at AGS and SPS energy range. We compare the
results of several experiments, looking for common trend in `participant
scaling' of production yields. We find a smooth description of scaled kaon and
yields as a function of participant density. We also show a participant
density dependence of kaons and produced in the forward hemisphere for
proton-nucleus collisions.Comment: Proceedings of the International Conference on Strangeness in Quark
Matter, 20-25 July 2000, Berkeley, CA. To appear in Journal of Physics G:
Nuclear and Particle Physic
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
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Second update The Gordon Bell Competetion entry gb110s2
Since the update to our entry of October 20th we have just made a significant improvement. We understand that this is past the deadline for updates and very close to the conference date. However, Lawrence Livermore National Laboratory has just updated the BG/L system software on their full 64 BG/L supercomputer to IBM-BGL Release 3. As we discussed in our update of October 20 this release includes our custom L1 and SRAM access functions that allow us to achieve higher sustained performance. Just a few hours ago we got access to the full system and obtained the fastest sustained performance point. In the full 131,072 CPU-cores system QCD sustains 70.9 Teraflops for the Dirac operator and 67.9 teraflops for the full Conjugate Gradient inverter. This is about 20% faster than our last update. We attach the corresponding speedup figure. As you can tell the speedup is perfect. This figure is the same as Figure 1 of our October 20th update except that it now includes the 131,072 CPU-cores point
Femtoscopy in Relativistic Heavy Ion Collisions: Two Decades of Progress
Analyses of two-particle correlations have provided the chief means for
determining spatio-temporal characteristics of relativistic heavy ion
collisions. We discuss the theoretical formalism behind these studies and the
experimental methods used in carrying them out. Recent results from RHIC are
put into context in a systematic review of correlation measurements performed
over the past two decades. The current understanding of these results is
discussed in terms of model comparisons and overall trends.Comment: 49 pages, 16 figures; to appear in Annual Review of Nuclear and
Particle Science; final version includes minor updates in text, a few
references added, and two figures updated; Figures and numerical data tables
available at http://www.physics.ohio-state.edu/~lisa/FemtoscopyReview2005
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
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
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