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

  • The first measurement of the e+e− pair production at low lepton pair transverse momentum (pT,ee) and low invariant mass (mee) 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 (|ηe|<0.8) as a function of invariant mass (0.4≤mee<2.7 GeV/c2) in the 50−70% and 70−90% centrality classes for pT,ee<0.1 GeV/c, and as a function of pT,ee in three mee intervals in the most peripheral Pb−Pb collisions. Below a pT,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 mee 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 pT,ee spectra. The measured ⟨p2T,ee⟩−−−−−√ of the excess pT,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.

Download full text files

Export metadata

Additional Services

Share in Twitter Search Google Scholar
Metadaten
URN:urn:nbn:de:hebis:30:3-822231
DOI:https://doi.org/10.48550/arXiv.2204.11732
ArXiv Id:http://arxiv.org/abs/2204.11732v1
Parent Title (English):arXiv
Series (Serial Number):CERN Report (CERN-EP-2022-068)
Publisher:arXiv
Document Type:Preprint
Language:English
Date of Publication (online):2022/04/25
Date of first Publication:2022/04/25
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Creating Corporation:ALICE (Körperschaft)
Release Date:2024/02/11
Issue:2204.11732 Version 1
Edition:Version 1
Page Number:19
HeBIS-PPN:516147331
Institutes:Physik / Physik
Informatik und Mathematik / Informatik
Wissenschaftliche Zentren und koordinierte Programme / Frankfurt Institute for Advanced Studies (FIAS)
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 4.0