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

Acharya, S. ; Basu, S. LU orcid ; Christiansen, P. LU ; Matonoha, O. LU ; Nassirpour, A.F. LU orcid ; Ohlson, A. LU ; Oskarsson, A. LU ; Richert, T. LU ; Rueda, O.V. LU and Silvermyr, D. LU orcid , et al. (2023) In Journal of High Energy Physics 2023(6).
Abstract
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... (More)
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). (Less)
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author collaboration
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Jets and Jet Substructure, Quark-Gluon Plasma
in
Journal of High Energy Physics
volume
2023
issue
6
article number
24
publisher
Springer
external identifiers
  • scopus:85163101135
ISSN
1029-8479
DOI
10.1007/JHEP06(2023)024
language
English
LU publication?
yes
id
936bfdf1-49ce-47c7-9eac-3e8a3f2d81ba
date added to LUP
2023-11-22 10:26:43
date last changed
2023-11-22 10:27:05
@article{936bfdf1-49ce-47c7-9eac-3e8a3f2d81ba,
  abstract     = {{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 | &lt; 0.8) as a function of invariant mass (0.4 ≤ m ee &lt; 2.7 GeV/c 2) in the 50–70% and 70–90% centrality classes for p T,ee &lt; 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).}},
  author       = {{Acharya, S. and Basu, S. and Christiansen, P. and Matonoha, O. and Nassirpour, A.F. and Ohlson, A. and Oskarsson, A. and Richert, T. and Rueda, O.V. and Silvermyr, D. and Staa, J. and Zurlo, N.}},
  issn         = {{1029-8479}},
  keywords     = {{Jets and Jet Substructure; Quark-Gluon Plasma}},
  language     = {{eng}},
  number       = {{6}},
  publisher    = {{Springer}},
  series       = {{Journal of High Energy Physics}},
  title        = {{Dielectron production at midrapidity at low transverse momentum in peripheral and semi-peripheral Pb–Pb collisions at √sNN = 5.02 TeV}},
  url          = {{http://dx.doi.org/10.1007/JHEP06(2023)024}},
  doi          = {{10.1007/JHEP06(2023)024}},
  volume       = {{2023}},
  year         = {{2023}},
}