13 Feb/24
11:00 - 12:15 (Europe/Zurich)

Dielectrons in Pb--Pb collisions with ALICE: Light from the little big bang


222/R-001 at CERN
Dielectrons are an exceptional tool for studying the evolution of the medium created in heavy-ion collisions as they are produced at all stages of the collision with negligible final-state interactions. In central collisions, the energy densities are sufficient to create a quark-gluon plasma (QGP). Thermal e+e− pairs radiating from this medium can be observed as an excess over the hadronic decay cocktail beyond the pion region.
For invariant masses above 1.2 GeV/𝑐2, correlated heavy-flavour (HF) hadron decays are expected to dominate the dielectron yield. Their contribution is modified in the medium compared to elementary collisions to an unknown extent, leading to large uncertainties in the subtraction of known hadronic sources. To control this contribution, a topological separation is crucial to disentangle the thermal dielectron from HF contributions.
In this seminar, the results of dielectron production in central Pb--Pb collisions at sqrt(𝑠)=5.02 TeV with ALICE in Run 2 will be presented. It is shown how recent advances of dielectron measurement in pp collision made this analysis possible. The measurements are compared to expectations from hadronic decays and calculations from theory. Finally, the topological separation of e+e− pairs is applied to extract a prompt thermal contribution in the intermediate-mass region.

Refreshments will be served at 10:30