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R. Vertesi

Publications and source records attributed to R. Vertesi.

7 recordsLinked to original sources
arXiv2019

Jet Structure Studies in Small Systems

A study investigating a possible jet shape dependence on the charged event multiplicity was performed on collision samples generated by Monte-Carlo (MC) event generators PYTHIA and HIJING++. We calculated the integral jet shape and found a significant modification caused by multiple-parton interactions. By interchanging and enabling different model ingredients in the simulations and analyzing the results in several $p_T$ bins and event multiplicity classes, we found a characteristic jet size measure that was independent of the chosen tunes, settings, and jet reconstruction algorithms.

hep-ph↗
arXiv2010

U_A(1) Symmetry Restoration from an In-Medium eta' Mass Reduction in sqrt(s(NN)) = 200 GeV Au+Au Collisions

A reduction of the mass of the eta'(958) meson may signal restoration of the U_A(1) symmetry in a hot and dense hadronic matter, corresponding to the return of the 9th, "prodigal" Goldstone boson. We report on an analysis of a combined PHENIX and STAR data set on the intercept parameter of the two-pion Bose-Einstein correlation functions, as measuremed in sqrt(s(NN)) = 200 GeV Au + Au collisions at RHIC. To describe this combined PHENIX and STAR dataset, an in-medium eta' mass reduction of at least 200 MeV is needed, at the 99.9 % confidence level in a broad model class of resonance abundances.

nucl-ex↗
arXiv2009

Indirect observation of an in-medium eta' mass reduction in sqrt(s_{NN})=200 GeV Au+Au collisions

PHENIX and STAR data on the intercept parameter of the two-pion Bose-Einstein correlation functions in sqrt(s_{NN}) = 200 GeV Au+Au collisions are analyzed in terms of different models of hadronic multiplicities. To describe this combined PHENIX and STAR dataset, an in-medium eta' mass reduction of at least 200 MeV is needed, at the 99.9 % confidence level in the considered model class. Such a significant eta' mass modification may indicate the restoration of the U_A(1) symmetry in a hot and dense hadronic matter and the return of the 9th "prodigal" Goldstone boson.

nucl-ex↗
arXiv2009

Significant in-medium eta' mass reduction in sqrt(s(NN))=200 GeV Au+Au collisions at the BNL Relativistic Heavy Ion Collider

In high energy heavy ion collisions a hot and dense medium is formed, where the U_A(1) or chiral symmetry may temporarily be restored. As a consequence, the mass of the eta'(958) mesons may be reduced to its quark model value, and the abundance of eta' mesons at low p_T may be enhanced by more than a factor of 10. The intercept parameter lambda_* of the charged pion Bose--Einstein correlations provides a sensitive observable of the possibly enhanced eta' abundance. We have analyzed lambda_*(m_T) data from sqrt(s(NN))=200 GeV central Au+Au reactions measured at the BNL Relativistic Heavy Ion Collider (RHIC), using extensive Monte Carlo simulations based on six popular models for hadronic multiplicities. Based on the combined STAR and PHENIX data set, and on various systematic investigations of resonance multiplicities and model parameters, we conclude that in sqrt(s(NN))=200 GeV central Au+Au reactions the mass of the eta' meson is reduced by Delta m > 200 MeV, at the 99.9% confidence level in the considered model class. Such a significant eta' mass modification may indicate the restoration of the U_A(1) symmetry in a hot and dense hadronic matter and the return of the ninth "prodigal" Goldstone boson. A similar analysis of NA44 S+Pb data at top CERN Super Proton Synchrotron (SPS) energies showed no significant in-medium eta' mass modification.

nucl-ex↗
arXiv2007

THERMINATOR simulations and PHENIX images of a heavy tail of particle emission in 200 GeV Au+Au collisions

Correlation between emitted particles from a thermalized medium carry important information about the space-time extent and the dynamics of the particle emitting source. Pion emission source functions S(r) have been measured in PHENIX using an imaging technique, and it has been found that it contains a heavy (power-law) tail. It leads us to the assumption that there is a halo of secondary pions, surrounding the core system that undergoes the hydrodynamical evolution. THERMINATOR, a Monte Carlo event generator designed for studies in relativistic heavy-ion collisions is used to model and investigate the influence of resonance decays on the tail of particle emission source. It lacks the implementation of rescattering, which, as we have learnt from previous Hadron Rescattering Code simulations, is a possible explanation of the power-law tail. Our studies also have shown that none of the pion sources alone are responsible for the tail: either the resonance decays or rescattering or a combination of these effects is a possible cause of the heavy tail.

nucl-th↗
arXiv2003

A Cosmic Ray Measurement Facility for ATLAS Muon Chambers

Monitored Drift Tube (MDT) chambers will constitute the large majority of precision detectors in the Muon Spectrometer of the ATLAS experiment at the Large Hadron Collider at CERN. For commissioning and calibration of MDT chambers, a Cosmic Ray Measurement Facility is in operation at Munich University. The objectives of this facility are to test the chambers and on-chamber electronics, to map the positions of the anode wires within the chambers with the precision needed for standalone muon momentum measurement in ATLAS, and to gain experience in the operation of the chambers and on-line calibration procedures. Until the start of muon chamber installation in ATLAS, 88 chambers built at the Max Planck Institute for Physics in Munich have to be commissioned and calibrated. With a data taking period of one day individual wire positions can be measured with an accuracy of 8.3 micrometers in the chamber plane and 27 micrometers in the direction perpendicular to that plane.

physics.ins-det↗