Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

Dielectron production in central Pb-Pb collisions at √sNN = 5.02 TeV

Acharya, S. ; Basu, S. LU orcid ; Christiansen, P. LU ; Hansen, J. LU orcid ; Iversen, K.E. LU orcid ; Matonoha, O. LU ; Nepeivoda, R. LU orcid ; Ohlson, A. LU ; Silvermyr, D. LU orcid and Staa, J. LU , et al. (2025) In Physical Review C 112(5).
Abstract
The first measurement of the e+e− pair production at midrapidity and low invariant mass in central Pb-Pb collisions at √sNN = 5.02 TeV at the Large Hadron Collider is presented. The yield of e+e− pairs is compared with a cocktail of expected hadronic decay contributions in the invariant mass (mee) and pair transverse momentum (pT,ee) ranges mee < 3.5 GeV/c2 and pT,ee < 8 GeV/c. For 0.18 < mee < 0.5 GeV/c2 the ratio of data to the cocktail of hadronic contributions amounts to 1.40 ± 0.11 (stat.) ± 0.23 (syst.) ± 0.16 (cocktail) and 1.42 ± 0.11 (stat.) ± 0.23 (syst.)+0.24−0.29 (cocktail), including or not including medium effects in the estimation of the heavy-flavor background, respectively. It is consistent with predictions... (More)
The first measurement of the e+e− pair production at midrapidity and low invariant mass in central Pb-Pb collisions at √sNN = 5.02 TeV at the Large Hadron Collider is presented. The yield of e+e− pairs is compared with a cocktail of expected hadronic decay contributions in the invariant mass (mee) and pair transverse momentum (pT,ee) ranges mee < 3.5 GeV/c2 and pT,ee < 8 GeV/c. For 0.18 < mee < 0.5 GeV/c2 the ratio of data to the cocktail of hadronic contributions amounts to 1.40 ± 0.11 (stat.) ± 0.23 (syst.) ± 0.16 (cocktail) and 1.42 ± 0.11 (stat.) ± 0.23 (syst.)+0.24−0.29 (cocktail), including or not including medium effects in the estimation of the heavy-flavor background, respectively. It is consistent with predictions from two different models for an additional contribution of thermal e+e− pairs from the hadronic and partonic phases. In the intermediate-mass range (1.2 < mee < 2.6 GeV/c2), the pair transverse impact parameter of the e+e− pairs (DCAee, where “DCA” denotes “distance of closest approach”) is used for the first time in Pb-Pb collisions to separate displaced dielectrons from heavy-flavor hadron decays from a possible (thermal) contribution produced at the interaction point. The data are consistent with a suppression of e+e− pairs from cc and an additional prompt component. Finally, the first direct-photon measurement in the 10% most central Pb-Pb collisions at √sNN = 5.02 TeV is reported via the study of virtual direct photons in the transverse momentum range 1 < pT < 5 GeV/c. A model including prompt photons, as well as photons from the preequilibrium and fluid-dynamic phases, can reproduce the result, while being at the upper edge of the data uncertainties. © 2025 CERN, for the ALICE Collaboration (Less)
Please use this url to cite or link to this publication:
author
; ; ; ; ; ; ; ; and , et al. (More)
; ; ; ; ; ; ; ; ; ; and (Less)
author collaboration
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review C
volume
112
issue
5
article number
054906
publisher
American Physical Society
external identifiers
  • scopus:105027404158
ISSN
2469-9985
DOI
10.1103/xl6m-vbqk
language
English
LU publication?
yes
id
6a61442b-de1f-4fd2-a3ae-5b0be99e79b3
date added to LUP
2026-04-07 13:08:01
date last changed
2026-04-07 13:08:42
@article{6a61442b-de1f-4fd2-a3ae-5b0be99e79b3,
  abstract     = {{The first measurement of the e+e− pair production at midrapidity and low invariant mass in central Pb-Pb collisions at √sNN = 5.02 TeV at the Large Hadron Collider is presented. The yield of e+e− pairs is compared with a cocktail of expected hadronic decay contributions in the invariant mass (mee) and pair transverse momentum (pT,ee) ranges mee &lt; 3.5 GeV/c2 and pT,ee &lt; 8 GeV/c. For 0.18 &lt; mee &lt; 0.5 GeV/c2 the ratio of data to the cocktail of hadronic contributions amounts to 1.40 ± 0.11 (stat.) ± 0.23 (syst.) ± 0.16 (cocktail) and 1.42 ± 0.11 (stat.) ± 0.23 (syst.)+0.24−0.29 (cocktail), including or not including medium effects in the estimation of the heavy-flavor background, respectively. It is consistent with predictions from two different models for an additional contribution of thermal e+e− pairs from the hadronic and partonic phases. In the intermediate-mass range (1.2 &lt; mee &lt; 2.6 GeV/c2), the pair transverse impact parameter of the e+e− pairs (DCAee, where “DCA” denotes “distance of closest approach”) is used for the first time in Pb-Pb collisions to separate displaced dielectrons from heavy-flavor hadron decays from a possible (thermal) contribution produced at the interaction point. The data are consistent with a suppression of e+e− pairs from cc and an additional prompt component. Finally, the first direct-photon measurement in the 10% most central Pb-Pb collisions at √sNN = 5.02 TeV is reported via the study of virtual direct photons in the transverse momentum range 1 &lt; pT &lt; 5 GeV/c. A model including prompt photons, as well as photons from the preequilibrium and fluid-dynamic phases, can reproduce the result, while being at the upper edge of the data uncertainties. © 2025 CERN, for the ALICE Collaboration}},
  author       = {{Acharya, S. and Basu, S. and Christiansen, P. and Hansen, J. and Iversen, K.E. and Matonoha, O. and Nepeivoda, R. and Ohlson, A. and Silvermyr, D. and Staa, J. and Vislavicius, V. and Zurlo, N.}},
  issn         = {{2469-9985}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review C}},
  title        = {{Dielectron production in central Pb-Pb collisions at √sNN = 5.02 TeV}},
  url          = {{http://dx.doi.org/10.1103/xl6m-vbqk}},
  doi          = {{10.1103/xl6m-vbqk}},
  volume       = {{112}},
  year         = {{2025}},
}