Soft-Dielectron Excess in Proton-Proton Collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msqrt><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msqrt><mml:mo>=</mml:mo><mml:mn>13</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:mrow></mml:math>

A measurement of dielectron production in proton-proton (pp) collisions at s=13 TeV, recorded with the ALICE detector CERN LHC, is presented this Letter. The data set was a reduced magnetic solenoid field. This enables investigation kinematic domain low (ee) invariant mass mee and pair transverse momentum pT,ee that previously inaccessible LHC. cross section for studied as function mee, pT,ee, event multiplicity dNch/dη. expected rate from hadron decays, called hadronic cocktail, utilizes parametrization measured η/π0 ratio pp proton-nucleus collisions, assuming shows no strong dependence on collision energy momentum. Comparison yield to cocktail 0.15<mee<0.6 GeV/c2 pT,ee<0.4 GeV/c indicates an enhancement soft dielectrons, reminiscent “anomalous” soft-photon soft-dilepton excess hadron-hadron reported by several experiments under different experimental conditions. factor over amounts 1.61±0.13(stat)±0.17(syst,data)±0.34(syst,cocktail) acceptance. Acceptance-corrected spectra are extracted compared calculations bremsstrahlung thermal radiation within many-body approach.Received 15 June 2020Revised 12 April 2021Accepted 8 2021DOI:https://doi.org/10.1103/PhysRevLett.127.042302Published American Physical Society terms Creative Commons Attribution 4.0 International license. Further distribution work must maintain attribution author(s) published article’s title, journal citation, DOI.© 2021 CERN, CollaborationPhysics Subject Headings (PhySH)Physical SystemsHigh-energy accelerators & collidersAccelerators Beams