München 2019 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 46: Hauptvorträge IV

HK 46.2: Hauptvortrag

Donnerstag, 21. März 2019, 11:35–12:10, Plenarsaal

Probing the Quark-Gluon Plasma with low-mass dileptons in heavy-ion collisions — •Raphaelle Bailhache — Institut für Kernphysik, Goethe-Universität Frankfurt

Ultrarelativistic heavy-ion collisions are used to study the physics of strongly interacting matter under extreme conditions, i.e. high temperature and density, similar to those of the early universe. In such collisions a deconfined state of quarks and gluons, the Quark-Gluon Plasma (QGP), is formed. Dileptons (e⁺e⁻, µ⁺µ⁻) provide an excellent probe of the QGP. Lepton pairs are emitted during all stages of the collision and carry information about the medium properties at the time of emission as they are unaffected by strong final-state interactions. The measurement of their invariant mass can be used to study the decay of massive particles, e.g. the in-medium modified spectral shape of ρ mesons related to the restoration of chiral symmetry. The latter is spontaneously broken in vacuum and accounts for most of the hadron masses. At the same time, thermal radiation from the medium, contributing over a broad mass range, gives insight into the temperature of the medium. Measurements of such signals are extremely challenging due to a large background from ordinary light- and heavy-flavour hadron decays.

This talk will review the low-mass dilepton measurements in heavy-ion collisions from SPS to LHC energies. In particular the latest results of ALICE at the LHC will be shown. Finally, future perspectives at the LHC and at facilities at lower energies will be shortly discussed.

Supported by BMBF and the Helmholtz Association.