Impact of the Coulomb field on charged-pion spectra in few-GeV heavy-ion collisions

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • HADES collaboration - (Author)
  • Chair of Hydrogen and Nuclear Energy
  • GSI Helmholtz Centre for Heavy Ion Research
  • Excellence Cluster ORIGINS
  • Technical University of Munich
  • Goethe University Frankfurt a.M.
  • Université Paris-Saclay
  • Joint Institute for Nuclear Research
  • University of Coimbra
  • Czech Academy of Sciences
  • Polish Academy of Sciences
  • Justus Liebig University Giessen
  • Helmholtz-Zentrum Dresden-Rossendorf
  • Slovak Academy of Sciences
  • Polytechnic Institute of Coimbra
  • Technische Universität Darmstadt
  • University of Santiago de Compostela
  • RAS - Institute for Nuclear Research
  • TUD Dresden University of Technology
  • Jagiellonian University in Kraków

Abstract

In nuclear collisions the incident protons generate a Coulomb field which acts on produced charged particles. The impact of these interactions on charged-pion transverse-mass and rapidity spectra, as well as on pion–pion momentum correlations is investigated in Au + Au collisions at sNN = 2.4 GeV. We show that the low-mt region (mt< 0.2 GeV/c2) can be well described with a Coulomb-modified Boltzmann distribution that also takes changes of the Coulomb field during the expansion of the fireball into account. The observed centrality dependence of the fitted mean Coulomb potential energy deviates strongly from a Apart2/3 scaling, indicating that, next to the fireball, the non-interacting charged spectators have to be taken into account. For the most central collisions, the Coulomb modifications of the HBT source radii are found to be consistent with the potential extracted from the single-pion transverse-mass distributions. This finding suggests that the region of homogeneity obtained from two-pion correlations coincides with the region in which the pions freeze-out. Using the inferred mean-square radius of the charge distribution at freeze-out, we have deduced a baryon density, in fair agreement with values obtained from statistical hadronization model fits to the particle yields.

Details

Original languageEnglish
Article number166
JournalEuropean Physical Journal A
Volume58
Issue number9
Publication statusPublished - Sept 2022
Peer-reviewedYes

Keywords

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