1,696 research outputs found
Initial temperature and EoS of quark matter from direct photons
The time evolution of the quark gluon plasma created in gold-gold collisions
of the Relativistic Heavy Ion Collider (RHIC) can be described by
hydrodynamical models. Distribution of hadrons reflects the freeze-out state of
the matter. To investigate the time evolution one needs to analyze penetrating
probes, such as direct photon spectra. Distributions of low energy photons was
published in 2010 by PHENIX. In this paper we analyze a 3+1 dimensional
solution of relativistic hydrodynamics and calculate momentum distribution of
direct photons. Using earlier fits of this model to hadronic spectra, we
compare photon calculations to measurements and find that the initial
temperature of the center of the fireball is at least 519+-12 MeV, while for
the equation of state we get c_s= 0.36+-0.02.Comment: Talk at the VI Workshop on Particle Correlations and Femtoscopy,
Kiev, September 14-18, 2010. 6 pages, 1 figure. This work was supported by
the OTKA grant NK73143 and M. Csanad's Bolyai scholarshi
Excitation function of elastic scattering from a unitarily extended Bialas-Bzdak model
The Bialas-Bzdak model of elastic proton-proton scattering assumes a purely
imaginary forward scattering amplitude, which consequently vanishes at the
diffractive minima. We extended the model to arbitrarily large real parts in a
way that constraints from unitarity are satisfied. The resulting model is able
to describe elastic scattering not only at the lower ISR energies but also
at 7 TeV in a statistically acceptable manner, both in the
diffractive cone and in the region of the first diffractive minimum. The total
cross-section as well as the differential cross-section of elastic
proton-proton scattering is predicted for the future LHC energies of
8, 13, 14, 15 TeV and also to 28 TeV. A non-trivial, significantly
non-exponential feature of the differential cross-section of elastic
proton-proton scattering is analyzed and the excitation function of the
non-exponential behavior is predicted. The excitation function of the shadow
profiles is discussed and related to saturation at small impact parameters.Comment: Talk by T. Csorgo presented at the WPCF 2014 conference, Gyongyos,
Hungary, August 25-29 201
Influence of finite volume and magnetic field effects on the QCD phase diagram
The Polyakov linear sigma model (PLSM) is used to investigate the respective
influence of a finite volume and a magnetic field on the quark-hadron phase
boundary in the plane of baryon chemical potential () vs. temperature
() of the QCD phase diagram. The calculated results indicate sizable shifts
of the quark-hadron phase boundary to lower values of
for increasing magnetic field strength, and an opposite shift to higher values
of for decreasing system volume. Such shifts could
have important implications for extraction of the thermodynamic properties of
the QCD phase diagram from heavy ion data
Higher order anisotropies in the Buda-Lund model: Disentangling flow and density field anisotropies
The Buda-Lund hydro model describes an expanding ellipsoidal fireball, and
fits the observed elliptic flow and oscillating HBT radii successfully. Due to
fluctuations in energy depositions, the fireball shape however fluctuates on an
event-by-event basis. The transverse plane asymmetry can be translated into a
series of multipole anisotropy coefficients. These anisotropies then result in
measurable momentum-space anisotropies, to be measured with respect to their
respective symmetry planes. In this paper we detail an extension of the
Buda-Lund model to multipole anisotropies and investigate the resulting flow
coefficients and oscillations of HBT radii.Comment: 1 column format, 20 pages, 10 figure
HBT radii from the multipole Buda-Lund model
The Buda-Lund model describes an expanding hydrodynamical system with
ellipsoidal symmetry and fits the observed elliptic flow and oscillating HBT
radii successfully. The ellipsoidal symmetry can be characterized by the second
order harmonics of the transverse momentum distribution, and it can be also
observed in the azimuthal oscillation of the HBT radii measured versus the
second order reaction plane. The model may have to be changed to describe the
experimentally indicated higher order asymmetries. In this paper we detail an
extension of the Buda-Lund hydro model to investigate higher order flow
harmonics and the triangular dependence of the azimuthally sensitive HBT radii.Comment: 4 pages, 6 figures. Presented at the 11th Workshop on Particle
Correlations and Femtoscopy (WPCF 2015), 03-07 Nov 2015, Warsaw, Polan
Direct photon observables from hydrodynamics and implications on the initial temperature and EoS
The expansion of the strongly interacting quark gluon plasma (sQGP) created
in Au+Au collisions at RHIC can be described by hydrodynamical models. Hadrons
are created after a freeze-out, thus their distribution describes the final
state of the evolution. The earlier stages can be analyzed via penetrating
probes like photon observables. These were measured in 2010 and 2011 by the
PHENIX experiment. Here we analyze an analytic, 1+3 dimensional perfect
relativistic hydrodynamic solution and calculate hadron and photon observables,
such as transverse momentum spectra, elliptic flow and correlation (HBT) radii.
We find that our model is not incompatible with the data, not even with the
direct photon elliptic flow. From fitting the data, we find that early
temperatures of the sQGP were well above the quark-hadron transition
temperature, in the hottest point, the center of the fireball the temperature
may have reached 507+-12 MeV. The equation of state of this quark matter can be
described by an average sound speed of 0.36+-0.02. We also predict a photon
source that is significantly larger in the out direction than in the side
direction.Comment: Presented at the VII Workshop on Particle Correlations and Femtoscopy
(WPCF2011), Tokyo, Japan, September 20-24, 201
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