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  • Dielectron production at mi...
    Al-Turany, M.; Alt, T.; Andrei, C.; Apadula, N.; Bailhache, R.; Bartsch, E.; Baruffaldi, F.; Bastid, N.; Bhasin, A.; Bianchi, N.; Biswas, S.; Bluhme, N.; Blume, C.; Bodova, T.; Boldizsár, L.; Borissov, A.; Bratrud, L.; Braun-Munzinger, P.; Bregant, M.; Buthelezi, Z.; Bylinkin, A.; Caliva, A.; Camacho, J. M. M.; Chakaberia, I.; Concas, M.; Conesa Balbastre, G.; Contreras, J. G.; Dainese, A.; Danu, A.; Del Grande, R.; Eisenhut, F.; Evans, D.; Faggin, M.; Faivre, J.; Fecchio, P.; Gaardhøje, J. J.; Gal, A.; Gianotti, P.; Gotovac, S.; Greiner, L.; Grigoras, C.; Grigoriev, V.; Harris, J. W.; Iddon, J. P.; Isakov, A.; Jung, J.; Jung, M.; Jusko, A.; Kaplin, V.; Kashyap, V.; Keijdener, D. L. D.; Khatun, A.; Kileng, B.; Kim, B.; Kim, M.; Kiselev, S.; Laudi, E.; Malaev, M.; Manzari, V.; Margagliotti, G. V.; Massacrier, L.; Mazzaschi, F.; Modak, A.; Mulligan, J. D.; Negru, A.; Nesbo, S. V.; Neskovic, G.; Nesterov, D.; Ogino, M.; Oppedisano, C.; Paul, B.; Pinsky, L.; Pinto, C.; Pop, A.; Ramello, L.; Riegler, W.; Rybicki, A.; Saetre, J.; Sahoo, B.; Sahu, D.; Sarkar, D.; Schweda, K.; Shangaraev, A.; Shigaki, K.; Shirinkin, S.; Slupecki, M.; Soncco, C.; Tersimonov, G.; Tieulent, R.; Timmins, A. R.; Torales-Acosta, F.; Trifiró, A.; Turrisi, R.; Ullaland, K.; Vasiliev, A.; Verweij, M.; Yoo, I.-K.; Zampolli, C.; Zanoli, H. J. C.; Zherebchevskii, V.

    The journal of high energy physics, 06/2023, Letnik: 2023, Številka: 6
    Journal Article

    A bstract 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 s NN = 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 p T , ee 2 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.