1,598 research outputs found
Harmonic expansion of the effective potential in Functional Renormalization Group at finite chemical potential
In this paper we propose a method to study the Functional Renormalization
Group at finite chemical potential. The method consists of mapping the FRG
equations within the Fermi surface into a differential equation defined on a
rectangle with zero boundary conditions. To solve this equation we use an
expansion of the potential in a harmonic basis. With this method we determined
the phase diagram of a simple Yukawa-type model; as expected, the bosonic
fluctuations decrease the strength of the transition.Comment: 15 pages, 10 figure
Heavy quarks or compactified extra dimensions in the core of hybrid stars
Neutron stars with extremely high central energy density are natural
laboratories to investigate the appearance and the properties of compactified
extra dimensions with small compactification radius, if they exist. Using the
same formalism, these exotic hybrid stars can be described as neutron stars
with quark core, where the high energy density allows the presence of heavy
quarks (c, b, t). We compare the two scenarios for hybrid stars and display
their characteristic features.Comment: Talk given at 4th International Workshop on New Worlds in
Astroparticle Physics, Faro, Portugal, 5-7, Sep 2002. 10 pages, 6 EPS figure
New Entropy Formula with Fluctuating Reservoir
Finite heat reservoir capacity and temperature fluctuations lead to
modification of the well known canonical exponential weight factor. Requiring
that the corrections least depend on the one-particle energy, we derive a
deformed entropy, K(S). The resulting formula contains the Boltzmann-Gibbs, the
Renyi and the Tsallis formulas as particular cases. For extreme large
fluctuations (compared to the Gaussian case) a new, parameter-free entropy -
probability relation emerges. This formula and the corresponding canonical
equilibrium distribution are nearly Boltzmannian for high probability, but
deviate from the classical result for low probability. In the extreme large
fluctuation limit the canonical distribution resembles for low probability the
cumulative Gompertz distribution
Pion production in d+Au collisions at RHIC energy
We present our results on neutral pion pi0 production in pp and dAu
collisions at RHIC energy. Pion spectra are calculated in a next-to-leading
order (NLO) perturbative QCD-based model. The model includes the transverse
component of the initial parton distribution (``intrinsic kT''). We compare our
results to the available experimental data from RHIC, and fit the data with
high precision. The calculation tuned this way is repeated for the dAu
collision, and used to investigate the interplay of shadowing and multiple
scattering at RHIC. The centrality dependence of the nuclear modification
factor shows a measurable difference between different shadowing
parameterizations.Comment: Final version published in the Eur. Phys. J. ST in the Proceedings of
the Zimanyi Memorial Workshop, 2-4 July, 2007, Budapest, Hungary; 12 pages in
Latex, 6 EPS figure
Differences in high p_t meson production between CERN SPS and RHIC heavy ion collisions
In this talk we present a perturbative QCD improved parton model calculation
for light meson production in high energy heavy ion collisions. In order to
describe the experimental data properly, one needs to augment the standard pQCD
model by the transverse momentum distribution of partons ("intrinsic k_T").
Proton-nucleus data indicate the presence of nuclear shadowing and
multiscattering effects. Further corrections are needed in nucleus-nucleus
collisions to explain the observed reduction of the cross section. We introduce
the idea of proton dissociation and compare our calculations with the SPS and
RHIC experimental data.Comment: Talk presented by G. Papp at Zakopane 2001 School, Zakopane, 2001
June; 10 pages with 3 EPS figure
Statistical Power Law due to Reservoir Fluctuations and the Universal Thermostat Independence Principle
Certain fluctuations in particle number at fixed total energy lead exactly to
a cut-power law distribution in the one-particle energy, via the induced
fluctuations in the phase-space volume ratio. The temperature parameter is
expressed automatically by an equipartition relation, while the q-parameter is
related to the scaled variance and to the expectation value of the particle
number. For the binomial distribution q is smaller, for the negative binomial q
is larger than one. These results also represent an approximation for general
particle number distributions in the reservoir up to second order in the
canonical expansion. For general systems the average phase-space volume ratio
expanded to second order delivers a q parameter related to the heat capacity
and to the variance of the temperature. However, q differing from one leads to
non-additivity of the Boltzmann-Gibbs entropy. We demonstrate that a deformed
entropy, K(S), can be constructed and used for demanding additivity. This
requirement leads to a second order differential equation for K(S). Finally,
the generalized q-entropy formula contains the Tsallis, Renyi and
Boltzmann-Gibbs-Shannon expressions as particular cases. For diverging
temperature variance we obtain a novel entropy formula.Comment: Talk given by T.S.Biro at Sigma Phi 2014, Rhodos, Greec
Jet Tomography Studies in AuAu Collision at RHIC Energies
Recent RHIC results on pion production in AuAu collision at sqrt(s)=130 and
200 AGeV display a strong suppression effect at high p_T. This suppression can
be connected to final state effects, namely jet energy loss induced by the
produced dense colored matter. Applying our pQCD-based parton model we perform
a quantitative analysis of the measured suppression pattern and determine the
opacity of the produced deconfined matter.Comment: Talk given at European Physical Society International Europhysics
Conference on High Energy Physics HEP2003, July 17-23. 2003, in Aachen,
Germany 3 pages in LaTeX, 2 EPS figure. (Accepted for publication in European
Physical Journal C direct
Perturbative QCD Results on Pion Production in pp, pA and AA Collisions
We summarize new pQCD results on pion production in proton-proton (pp),
proton-nucleus (pA) and nucleus-nucleus (AA) collisions. Our calculation
introduces intrinsic parton transverse momentum (k_T) and is performed
effectively at next-to-leading order (NLO), applying a K factor extracted for
jet events. Two different factorization scales, Q=p_{T,jet}/2 and p_{T,jet} are
used. Experimental data in pA collisions imply a preference for the latter
choice at NLO level. We display our results at CERN SPS for AA collisions.Comment: Talk given at Budapest Workshop on Quark and Hadron Dynamics in
Relativistic Heavy Ion Collisions (BP 2002) Budapest, Hungary, 3-7 Mar 2002.
11 pages in Latex, 7 PS figure. Submitted to Heavy Ion Physic
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