München 2019 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 26: Heavy-Ion Collisions and QCD Phases V

HK 26.4: Talk

Tuesday, March 19, 2019, 17:30–17:45, HS 15

Low-mass dielectron measurements in high-multiplicity pp collisions with ALICE at the LHC — •Ivan Vorobyev for the ALICE collaboration — Technische Universität München

Electron-positron pairs produced in ultra-relativistic heavy-ion collisions at the LHC carry important information about the system space-time evolution unperturbed by strong final-state interactions. Measurements of the dielectron continuum in inelastic proton-proton collisions serve as an important vacuum reference for the heavy-ion studies. However, proton-proton collisions with high charged-particle multiplicities recently have been found to exhibit interesting phenomena, such as the longitudinal structure in the two-dimensional angular correlation and the enhanced production of strange and heavy-flavour hadrons. Measurements of low-mass dielectrons could provide additional information regarding the underlying physics processes in high-multiplicity pp collisions.

In this talk, we present the latest results of the dielectron analysis with ALICE in pp collisions at √s = 13 TeV. A particular focus of the discussion is put on the modification of dielectron spectrum in pp collisions collected with a trigger on high charged-particle multiplicities with respect to the inelastic events. The relative increase of dielectron production in high-multiplicity events is compared to the expectations from already measured multiplicity-dependent production of light and heavy hadrons. The production of direct photons in inelastic and high-multiplicity collisions is also discussed.