Multiharmonic Correlations of Different Flow Amplitudes in Pb-Pb Collisions at √sNN=2.76 TeV



Acharya, S, Adamova, D, Adler, A, Adolfsson, J, Rinella, G Aglieri, Agnello, M, Agrawal, N, Ahammed, Z, Ahmad, S, Ahn, SU
et al (show 993 more authors) (2021) Multiharmonic Correlations of Different Flow Amplitudes in Pb-Pb Collisions at √sNN=2.76 TeV PHYSICAL REVIEW LETTERS, 127 (9). 042302-. ISSN 0031-9007, 1079-7114

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Abstract

A measurement of dielectron production in proton-proton (pp) collisions at s=13 TeV, recorded with the ALICE detector at the CERN LHC, is presented in this Letter. The data set was recorded with a reduced magnetic solenoid field. This enables the investigation of a kinematic domain at low dielectron (ee) invariant mass mee and pair transverse momentum pT,ee that was previously inaccessible at the LHC. The cross section for dielectron production is studied as a function of mee, pT,ee, and event multiplicity dNch/dη. The expected dielectron rate from hadron decays, called hadronic cocktail, utilizes a parametrization of the measured η/π0 ratio in pp and proton-nucleus collisions, assuming that this ratio shows no strong dependence on collision energy at low transverse momentum. Comparison of the measured dielectron yield to the hadronic cocktail at 0.15<mee<0.6 GeV/c2 and for pT,ee<0.4 GeV/c indicates an enhancement of soft dielectrons, reminiscent of the "anomalous"soft-photon and soft-dilepton excess in hadron-hadron collisions reported by several experiments under different experimental conditions. The enhancement factor over the hadronic cocktail amounts to 1.61±0.13(stat)±0.17(syst,data)±0.34(syst,cocktail) in the ALICE acceptance. Acceptance-corrected excess spectra in mee and pT,ee are extracted and compared with calculations of dielectron production from hadronic bremsstrahlung and thermal radiation within a hadronic many-body approach.

Item Type: Article
Uncontrolled Keywords: A Large Ion Collider Experiment Collaboration
Divisions: Faculty of Science & Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 16 Dec 2021 13:46
Last Modified: 16 Jun 2026 14:08
DOI: 10.1103/PhysRevLett.127.092302
Open Access URL: https://journals.aps.org/prl/abstract/10.1103/Phys...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3145500
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