Naslov
Soft-Dielectron Excess in Proton-Proton Collisions at √s=13  TeV

Autori
Acharya, S. ; ... ; Antičić, Tome ; ... ; Erhardt, Filip ; ... ; Gotovac, Sven ; ... ; Jerčić, Marko ; ... ; Karatović, David ; ... ; Lončar, Petra ; ... ; Mudnić, Eugen ; ... ; Planinić, Mirko ; ... ; Poljak, Nikola ; ... ; Vicković, Linda ; ... ; Zurlo, N.

Kolaboracija
ALICE Collaboration

Izvornik
Physical review letters (0031-9007) 127 (2021), 4; 042302, 13

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
p p: scattering ; bremsstrahlung: hadronic ; transverse momentum: low ; p nucleus: scattering ; radiation: thermal ; hadron: decay ; hadron hadron: scattering ; CERN LHC Coll ; enhancement ; ALICE ; many-body problem ; parametrization ; multiplicity ; acceptance ; kinematics ; experimental results ; 13000 GeV-cms/nucleon

Sažetak
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 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 (p-A) 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/c^2 and for pT, ee<0.4 GeV/c indicates an enhancement of soft dielectrons, reminiscent of the 'anomalous' soft-photon and -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.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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