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P. Levai

Publications and source records attributed to P. Levai.

At least 37 records · Page 2Linked to original sources
arXiv2007

Does the Cronin Peak Disappear at LHC Energies?

In this work we compare the nuclear modification factors in proton (deuteron) -- nucleus collisions at CERN SPS, FNAL and RHIC energies in a wide p_T range. In these experiments the nuclear modification factor has shown an enhancement at p_T ~ 4 GeV/c. The height of this "Cronin peak" depends on the c.m. energy of the collision, as it is subject to stronger shadowing at higher energies. One of the aims of this contribution is to analyze the shadowing phenomenon at lower (2 GeV/c < p_T < 4 GeV/c) and intermediate (4 GeV/c < p_T < 8 GeV/c) transverse momentum. Different shadowing parameterizations are considered and the obtained Cronin peaks are investigated at RHIC and LHC energies.

hep-ph↗
arXiv2007

The mass distribution of quark matter

We analyze lattice QCD results on the equation of state in terms of infinitely many non-interacting massive ideal gas components. We find that the entire pressure-temperature curve can be described by a temperature independent mass distribution at vanishing chemical potential. We collect strong indications for a mass gap in this distribution, conjectured to be related confinement.

hep-ph↗
arXiv2007

EMC effect and jet energy loss in relativistic deuteron-nucleus collisions

We investigate the influence of modified nuclear parton distribution functions (PDFs) on high-pT hadron production at RHIC and LHC energies using a pQCD-improved parton model. For application at RHIC, we focus on the possible contribution of the EMC modification of the nuclear PDFs in the x > 0.3 region to the observed suppression of pi0 production at pT > 10 GeV/c in dAu collisions. We study three different parameterizations of the nuclear PDF modifications and find that they give consistent results for R_dAu(pT) for neutral pions in the region 10 GeV/c < pT < 20 GeV/c. We find that the EMC suppression of the parton distributions in the Au nucleus does not strongly influence the R_dAu for pi0 in the pT region where the suppression is observed. Using the HKN parameterization, we evaluate systematic errors in the theoretical R_dAu(pT) resulting from uncertainties in the nuclear PDFs. The measured nuclear modification factor is inconsistent with the pQCD model result for pT > 10 GeV/c even when the systematic uncertainties in the nuclear PDFs are accounted for. The inclusion of a small final-state energy loss can reduce the discrepancy with the data, but we cannot perfectly reproduce the pT dependence of the measured R_dAu(pT). For the LHC, we find that shadowing of the nuclear PDFs produces a large suppression in the yield of hadrons with pT < 100 GeV/c in p(d)A collisions.

hep-ph↗
arXiv2006

Nuclear effects in dAu collisions from recent RHIC data

Neutral pion (pi0) production is calculated in a leading order (LO) perturbative QCD-based model in pp and dAu collisions at s^1/2=200 AGeV at midrapidity. The model includes the transverse component of the initial parton distribution. We compare our results for pp collision to experimental data at RHIC energy. We repeat our calculation for the dAu collision and investigate the interplay between shadowing and multiple scattering. In central $]dAu collisions the influence of possible jet energy loss on cold nuclear matter is discussed and numerical results are displayed.

nucl-th↗
arXiv2006

Equation of state for distributed mass quark matter

We investigate how the QCD equation of state can be reconstructed by a continous mass distribution of non-interacting ideal components. We find that adjusting the mass scale as a function of the temperature leads to results which are conform to the quasiparticle model, but a temperature independent distribution also may fit lattice results. The fitted mass distribution tends to show a mass gap, supporting the physical picture of the quark coalescence in hadronization.

hep-ph↗
arXiv2006

Di-hadron correlations at ISR and RHIC energies

The structure of hadron-hadron correlations is investigated in proton-proton collisions.We focus on the transmission of the initial transverse momenta of partons (``intrinsic $k_T$'') to the hadron-hadron correlations. Values of the intrinsic transverse momentum obtained from experimental correlations are compared to the results of a model with partially randomized parton transverse momenta at ISR and RHIC energies. Procedures for extracting the correlations from data are discussed.

hep-ph↗
arXiv2006

The phases of strongly interacting matter in heavy ion collisions

In ultrarelativistic heavy ion collisions the produced high temperature, high energy density state will cross different phases of the strongly interacting matter. The original idea of quark-gluon plasma formation has been evolved and the weakly interacting gaseous state of massless partons has been replaced by the picture of strongly interacting massive constituent quarks. Experimental results at SPS and RHIC supports this idea. We discuss the phases at LHC energies.

nucl-th↗
arXiv2006

Molecular dynamics simulation of strongly coupled QCD plasmas

The properties of a strongly interacting quark plasma are investigated by molecular dynamics method including non-abelian quark-quark potential. Our main goal is to study the thermalization process in this system. We find an interesting resonance-like behaviour: at a characteristic time close to the inverse plasma frequency the quark plasma is heated up substantially via energy transfer from quark potential energy into one particle kinetic energy. Color rotation mechanism enhances the effectivity of this heating process, leading to a very fast thermalization with high temperature.

nucl-th↗
arXiv2005

The Nuclear Modification Factor at Large Rapidities

RHIC data on high-$p_T$ hadron production display strong suppression in a wide rapidity region, indicating strong induced energy loss for both transversally and longitudinally traveling partons. We investigate the interplay of energy loss and rapidity dependence in a perturbative QCD improved parton model, and estimate the opacity of the produced hot matter in $AuAu$ collisions at energies $\sqrt{s}=200$ $A$GeV and 63 $A$GeV at different rapidity values. Direction-dependent suppression offers the possibility to study the geometry of the hot matter.

hep-ph↗
arXiv2005

Properties of quark matter produced in heavy ion collision

We describe the hadronization of quark matter assuming that quarks creating hadrons coalesce from a continuous mass distribution. The pion and antiproton spectrum as well as the momentum dependence of the antiproton to pion ratio are calculated. This model reproduces fairly well the experimental data at RHIC energies.

nucl-th↗
arXiv2004

Transverse momentum spectra of fermions and bosons produced in strong abelian fields

We study the transverse momentum spectra of fermions and bosons produced in strong, time-dependent abelian field. The transverse size of the abelian field is finite, similarly to color strings and ropes. Different time-dependent field strengths are investigated in a kinetic model, and transverse momentum spectra are calculated for fermions and bosons. These spectra display exponential or polynomial behavior at high p_T, depending on the given time dependence. We compare our spectra to lattice result for a classical gluon field and obtain surprisingly good agreement in certain cases.

hep-ph↗
arXiv2004

Energy dependence of transverse quark flow in heavy ion collisions

Energy dependence of quark transverse flow carries information about dynamical properties (equation of state, initial conditions) of deconfined matter produced in heavy ion collisions. We assume quark-antiquark matter formation in Pb+Pb collisions at CERN SPS and Au+Au collisions at RHIC energies and determine quark transverse flow at the critical temperature of the quark-hadron phase transition. Coalescence of massive quarks is calculated in the MICOR hadronization model and hadronic final state effects are considered using the GROMIT cascade program. Comparing theoretical results to data, transverse flow values are determined and energy dependence is discussed.

nucl-th↗
arXiv2004

Photon Physics in Heavy Ion Collisions at the LHC

Various pion and photon production mechanisms in high-energy nuclear collisions at RHIC and LHC are discussed. Comparison with RHIC data is done whenever possible. The prospect of using electromagnetic probes to characterize quark-gluon plasma formation is assessed.

hep-ph↗
arXiv2004

Cronin Effect at Different Rapidities at RHIC

Calculations of the nuclear modification factor, R_dAu, for pi^0 production in dAu collisions at s_NN^1/2 = 200 GeV are presented. The applied pQCD-improved parton model incorporates intrinsic k_T. Nuclear multiscattering and nuclear shadowing are considered in the Au nucleus. Theoretical results are displayed for midrapidity and high pseudorapidity (eta), and compared to preliminary PHENIX and BRAHMS data.

nucl-th↗
arXiv2004

Quark coalescence into opposite parity baryon states

The production rate of negative parity baryons was found to be much weaker than that of positive states in RHIC experiments. In the present paper we show that this suppression is a simple consequence of the coalescence dynamics of hadronization.

nucl-th↗
arXiv2003

The inner structure of hybrid stars

Hybrid stars with extremely high central energy density in their core are natural laboratories to investigate the appearance and the properties of compactified extra dimensions with small compactification radius -- if these extra dimensions exist at all. We introduce the necessary formalism to describe quantitatively these objects and the properties of the formed hydrostatic equilibrium. Different scenarios of the extra dimensions are discussed and the characteristic features of these hybrid stars are calculated.

astro-ph↗
arXiv2003

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.

astro-ph↗