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1
Content available remote Refractive index of light and the quark-gluon plasma
100%
Liu J. , Luo M.-J. , Xu H.-J.
Open Physics
|
2012
|
tom 10
|
nr 6
1369-1371
EN
The refractive index (RI) of light propagating in a medium of quark-gluon plasma (QGP) is studied. The weakly coupled QGP is studied in the framework of hard-thermal-loop (HTL) perturbation theory, and the strongly coupled one is treated based on the holographic approach. In more realistic setups, the feasibility of observing the optical phenomenon related to the RI of QGP is also discussed.
2
Content available remote Dilepton creation based on an analytic hydrodynamic solution
80%
Csanád M. , Krizsán L.
Open Physics
|
2014
|
tom 12
|
nr 2
132-140
EN
High-energy collisions of various nuclei, so called “Little Bangs” are observed in various experiments of heavy ion colliders. The time evolution of the strongly interacting quark-gluon plasma created in heavy ion collisions can be described by hydrodynamical models. After expansion and cooling, the hadrons are created in a freeze-out. Their distribution describes the final state of this medium. To investigate the time evolution one needs to analyze penetrating probes, such as direct photon or dilepton observables, as these particles are created throughout the evolution of the medium. In this paper we analyze an 1+3 dimensional analytic solution of relativistic hydrodynamics, and we calculate dilepton transverse momentum and invariant mass distributions. We investigate the dependence of dilepton production on time evolution parameters, such as emission duration and equation of state. Using parameters from earlier fits of this model to photon and hadron spectra, we compare our calculations to measurements as well. The most important feature of this work is that dilepton observables are calculated from an exact, analytic, 1+3D solution of relativistic hydrodynamics that is also compatible with hadronic and direct photon observables.
3
Content available remote What favors and disfavors the critical point of QCD?
80%
Fukushima K.
Open Physics
|
2012
|
tom 10
|
nr 6
1318-1321
EN
Results from chiral effective models suggest the existence of the so-called QCD critical point. These model predictions are highly dependent on the model setup and there is no universal argument for its existence and location. I discuss why a first-order phase transition is generally favored in models at low temperature T and high chemical potential µ, which will explain why the model results are unreliable about the critical point. I propose a useful way to reinterpret the model results as a liquid-gas-type phase transition like that of nuclear matter. This picture provides us with a fairly model-independent description of the QCD critical point not relying on detailed phase structures.
4
Content available Buda-Lund hydro model and the elliptic flow at RHIC
80%
Csanád M. , Csörgo T. , Lörstad B. , Ster A.
Nukleonika
|
2004
|
tom Vol. 49,suppl.2
45-48
EN
The ellipsoidally symmetric Buda-Lund hydrodynamic model describes naturally the transverse momentum and the pseudorapidity dependence of the elliptic flow in Au+Au collisions at sNN = 130 and 200 GeV. The result confirms the indication of quark deconfinement in Au+Au collisions at RHIC, obtained from Buda-Lund hydro model fits to combined spectra and HBT radii of BRAHMS, PHOBOS, PHENIX and STAR.
5
Content available remote Equation of state and initial temperature of quark gluon plasma at RHIC
80%
Csanád M. , Májer I.
Open Physics
|
2012
|
tom 10
|
nr 4
850-857
EN
In gold-gold collisions of the Relativistic Heavy Ion Collider a perfect fluid of strongly interacting quark gluon plasma (sQGP) is created. The time evolution of this fluid can be described by hydrodynamical models. After an expansion, hadrons are created during the freeze-out period. Their distribution reveals information about the final state. To investigate the time evolution one needs to analyze penetrating probes: e.g. direct photon observations. In this paper we analyze a 1+3 dimensional solution of relativistic hydrodynamics. We calculate momentum distribution, azimuthal asymmetry and momentum correlations of direct photons. Based on earlier fits to hadronic spectra, we compare photon calculations to measurements to determine the equations of state and the initial temperature of sQGP. We find that the initial temperature in the center of the fireball is 507±12 MeV, while for the sound speed we get c s=0.36±0.02. We also estimate a systematic error of these results. We find that the measured azimuthal asymmetry is also compatible with this model. We also predict a photon source that is significantly larger in the out direction than in the side direction.
6
Content available remote Baryon number cumulants and proton number cumulants in relativistic heavy ion collisions
80%
Asakawa M.
Open Physics
|
2012
|
tom 10
|
nr 6
1314-1317
EN
Baryon number cumulants are invaluable tools to diagnose the primordial stage of heavy ion collisions. In experiments, however, proton number cumulants have been measured as substitutes. In fact, proton number fluctuations are further modified in the hadron phase and different from those of baryon number. We give formulas that express the baryon number cumulants solely in terms of proton number fluctuations, which are experimentally observable.
7
Content available Elliptic flow at RHIC with NeXSPheRIO
80%
Andrade R. , Grassi F. , Hama Y. , Kodama T. , Socolovski Jr. O. , Tavares B.
Nukleonika
|
2006
|
tom Vol. 51,suppl.3
17-20
EN
Elliptic flow at RHIC is computed event-by-event with NeXSPheRIO. Reasonable agreement with experimental results on v2(h) is obtained. Various effects are studied as well: reconstruction of impact parameter direction, freeze-out temperature, equation of state (with or without crossover), emission mechanism.
8
Content available Charge transfer fluctuations as a QGP signal
80%
Jeon S. , Shi L. , Bleicher M.
Nukleonika
|
2006
|
tom Vol. 51,suppl.3
65-68
EN
In this study, we analyze the recently proposed charge transfer fluctuations within a finite pseudorapidity space. As the charge transfer fluctuation is a measure of the local charge correlation length, it is capable of detecting inhomogeneity in the hot and dense matter created by heavy-ion collisions. We predict that going from peripheral to central collisions, the charge transfer fluctuations at midrapidity should decrease substantially while the charge transfer fluctuations at the edges of the observation window should decrease by a small amount. These are consequences of having a strongly inhomogeneous matter where the QGP component is concentrated around midrapidity. We also show how to constrain the values of the charge correlations lengths in both the hadronic phase and the QGP phase using the charge transfer fluctuations. Current manuscript is based on the two recent papers [10, 13].
9
Content available remote Determination of freeze-out conditions from lattice QCD calculations
80%
Karsch F.
Open Physics
|
2012
|
tom 10
|
nr 6
1234-1237
EN
Freeze-out conditions in Heavy Ion Collisions are generally determined by comparing experimental results for ratios of particle yields with theoretical predictions based on applications of the Hadron Resonance Gas model. We discuss here how this model dependent determination of freeze-out parameters may eventually be replaced by theoretical predictions based on equilibrium QCD thermodynamics.
10
Content available Hadron resonance probes of QGP
70%
Torrieri G. , Rafelski J.
Nukleonika
|
2004
|
tom Vol. 49,suppl.2
109-114
EN
We discuss the indirect and direct role of the short-lived resonances as probes of QGP freeze-out process. The indirect effect is the distortion of stable single particle yields and spectra by contributions of decaying resonances, which alter significantly the parameters obtained in fits to experimental data. We then discuss the direct observation of short-lived resonances as a probe of post-hadronization dynamics allowing to distinguish between different hadronization models.
11
Content available remote Hard-thermal-loop QCD trace anomaly
70%
Su N.
Open Physics
|
2012
|
tom 10
|
nr 6
1379-1381
EN
In this proceedings I summarize results of QCD trace anomaly from recent three-loop hard-thermal-loop perturbation theory (HTLpt) calculations. I focus on the trace anomaly scaled by T 2 for pure-glue and N f = 3 QCD. The comparison to available lattice data suggests that for pure-glue QCD agreement between HTLpt results and lattice data for the trace anomaly begins at temperatures above 8 T c while when including quarks (N f = 3) agreement begins already at temperatures above 2 T c. The results in both cases indicate that at very high temperatures the T 2-scaled trace anomaly increases with temperature in accordance with the predictions of HTLpt.
12
Content available Particle correlations to be seen by ALICE
60%
Pluta J. , Chajęcki Z. , Gos H. , Skowroński P.
Nukleonika
|
2004
|
tom Vol. 49,suppl.2
103-108
EN
The possibilities of ALICE experiment in measurements of particle correlations are estimated by computer simulations. A dedicated software has been created with the aim to study the influence of different experimental factors on the shape of correlation functions and with the intention to serve in the future for the analysis of real data. A scheme of correlation analysis is described shortly and some of the first results are presented. This analysis is being performed in the frame of ALICE "Physics Performance Report".
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