Event-by-event investigation of the two-particle source function in heavy-ion collisions with EPOS

Abstract

Exploring the shape of the pair-source function for particles such as pions or kaons has been an important goal of heavy-ion physics, and substantial effort has been made in order to understand the underlying physics behind the experimental observations of non-Gaussian behavior. In experiments, since no direct measurement of the source function is possible, quantum-statistical momentum correlations are utilized to gain information about the space-time geometry of the particle emitting source. Event generators, such as EPOS, however, provide direct access to the freeze-out coordinates of final state particles, and thus the source function can be constructed and investigated. The EPOS model is a sophisticated hybrid model where the initial stage evolution of the system is governed by Parton-Based Gribov-Regge theory, and subsequently a hydrodynamic evolution is utilized, followed by hadronization and hadron dynamics. EPOS has already proven to be successful in describing several different experimental observations for systems characterized by baryon chemical potential close to zero, but so far the source shape has not been explored in detail. In this paper we discuss an event-by-event analysis of the two-particle source function in $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions generated by the EPOS model. We find that when utilizing all stages of the model, Lévy-shaped distributions (unlike Gaussian distributions) provide a good description of the source shape in the individual events. Hence it is clear that it is not the event averaging that creates the non-Gaussian features in the pair distributions. Based on this observation, we determine Lévy-parameters of the source as a function of event centrality and particle momentum.

arXiv comment13 pages, 6 figures

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Cited by in corpus (16)

• Event-by-event investigation of the two-particle source function in $\sqrt{s_{{}_{\text{NN}}}}=2.76$ TeV PbPb collisions with EPOS
• Femtoscopy with Lévy sources from SPS through RHIC to LHC
• A novel method for calculating Bose-Einstein correlation functions with Coulomb final-state interaction
• Pion interferometry with Lévy-stable sources in $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions at STAR
• Femtoscopic correlation measurement with symmetric Lévy-type source at NA61/SHINE
• Two-particle Bose-Einstein correlations and their Lévy parameters in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Centrality dependence of Lévy-stable two-pion Bose-Einstein correlations in $\sqrt{s_{{}_{NN}}}=200$ GeV Au$+$Au collisions
• Kaon femtoscopy with Lévy-stable sources from $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC
• Kaonic Hanbury-Brown-Twiss radii at 200 GeV and 5.02 TeV
• Centrality-dependent Lévy HBT analysis in $\sqrt{s_{{}_{\text{NN}}}}=5.02$ TeV PbPb collisions at CMS
• Femtoscopy at NA61/SHINE using symmetric Lévy sources in central ${}^{40}$Ar+${}^{45}$Sc from 40$A$ GeV/$c$ to 150$A$ GeV/$c$
• Investigating the excitation function of HBT radii for Lévy-stable sources
• Three-dimensional sizes and shapes of pion emission in heavy-ion collisions
• Femtoscopy analysis in small systems at NA61/SHINE
• Geometry of particle emission in UrQMD Ar+Sc collisions at SPS energies
• Multi-dimensional investigation of the pion pair-source in heavy-ion collisions with EPOS