München 2019 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 26: Heavy-Ion Collisions and QCD Phases V

HK 26.1: Gruppenbericht

Dienstag, 19. März 2019, 16:30–17:00, HS 15

Results of low-mass dielectron measurements in pp, p–Pb and Pb–Pb collisions with ALICE at the LHC — •Torsten Dahms for the ALICE collaboration — Excellence Cluster Universe - TUM, Garching, Germany

Low-mass e⁺e⁻ pairs (dielectrons) are a particularly useful probe to study the hot and dense medium created in ultra-relativistic heavy-ion collisions. Such pairs are produced during all stages of the collision and carry information about the whole space-time evolution of the system, unperturbed by strong final-state interactions.

The invariant-mass continuum of dielectrons is extremely rich in physics sources: on top of ordinary in-vacuum decays of light and heavy-flavour hadrons, the contributions from thermal radiation and a modified ρ meson due to the predicted restoration of chiral symmetry in heavy-ion collisions are of great interest. However, it is first necessary to understand the very large background of correlated dielectron pairs from semi-leptonic charm and beauty hadron decays. Dielectron measurements in pp and p–Pb collisions serve as crucial vacuum and cold nuclear matter references needed for the heavy-ion studies. Here, the intermediate-mass region provides insight into heavy-flavour production complementary to single heavy-flavour hadron measurements.

We present an overview of the latest results on low-mass dielectron production from the ALICE Collaboration in pp, p–Pb and central Pb–Pb collisions at various energies. The implications for heavy-flavour and (thermal) direct photon production will be discussed. Finally, perspectives for the LHC Run-3 will be shortly mentioned.