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Sumit Basu (Lund University)

Sumit Basu

Postdoctoral Researcher

Sumit Basu (Lund University)

Dielectron production at midrapidity at low transverse momentum in peripheral and semi-peripheral Pb–Pb collisions at √sNN = 5.02 TeV

Author

  • S. Acharya
  • S. Basu
  • P. Christiansen
  • O. Matonoha
  • A.F. Nassirpour
  • A. Ohlson
  • A. Oskarsson
  • T. Richert
  • O.V. Rueda
  • D. Silvermyr
  • J. Staa
  • N. Zurlo
Show all

Summary, in English

The first measurement of the e+e− pair production at low lepton pair transverse momentum (p T,ee) and low invariant mass (m ee) in non-central Pb–Pb collisions at sNN = 5.02 TeV at the LHC is presented. The dielectron production is studied with the ALICE detector at midrapidity (|η e | < 0.8) as a function of invariant mass (0.4 ≤ m ee < 2.7 GeV/c 2) in the 50–70% and 70–90% centrality classes for p T,ee < 0.1 GeV/c, and as a function of p T,ee in three m ee intervals in the most peripheral Pb–Pb collisions. Below a p T,ee of 0.1 GeV/c, a clear excess of e+e− pairs is found compared to the expectations from known hadronic sources and predictions of thermal radiation from the medium. The m ee excess spectra are reproduced, within uncertainties, by different predictions of the photon–photon production of dielectrons, where the photons originate from the extremely strong electromagnetic fields generated by the highly Lorentz-contracted Pb nuclei. Lowest-order quantum electrodynamic (QED) calculations, as well as a model that takes into account the impact-parameter dependence of the average transverse momentum of the photons, also provide a good description of the p T,ee spectra. The measured 〈pT,ee2〉 of the excess p T,ee spectrum in peripheral Pb–Pb collisions is found to be comparable to the values observed previously at RHIC in a similar phase-space region. [Figure not available: see fulltext.]. © 2023, The Author(s).

Department/s

  • Particle and nuclear physics

Publishing year

2023

Language

English

Publication/Series

Journal of High Energy Physics

Volume

2023

Issue

6

Document type

Journal article

Publisher

Springer

Topic

  • Subatomic Physics

Keywords

  • Jets and Jet Substructure
  • Quark-Gluon Plasma

Status

Published

ISBN/ISSN/Other

  • ISSN: 1029-8479