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HK: Fachverband Physik der Hadronen und Kerne
HK 46: Heavy-Ion Collisions and QCD Phases XI
HK 46.4: Vortrag
Mittwoch, 13. März 2024, 16:30–16:45, HBR 62: EG 18
Polarization of thermal dilepton radiation — •Florian Seck1, B. Friman2,1, T. Galatyuk2,1, H. van Hees3,4, E. Speranza5, R. Rapp6, and J. Wambach1 — 1Technische Universität Darmstadt — 2GSI, Darmstadt — 3Universität Frankfurt — 4Helmholtz Research Academy Hesse for FAIR, Frankfurt — 5Theoretical Physics Department, CERN, Switzerland — 6Texas A&M University, College Station, USA
Multi-differential measurements of dilepton spectra serve as a unique tool to characterize the properties of matter in the interior of the hot and dense fireball. An important property of virtual photons is their spin polarization defined in the rest frame of the virtual photon for a chosen quantization axis. While the total yield and observable spectra are proportional to the sum of the longitudinal and transverse components of the spectral function, the polarization depends on their difference. As the processes that drive the medium effects in the spectral function change with invariant mass and momentum, this becomes a powerful tool for studying the medium composition.
In this contribution, we present the polarization observables of thermal virtual photons as a function of mass and momentum, compare the results to existing measurements from HADES and NA60, and provide predictions for upcoming HADES data. Finally, we discuss the prospects of using dilepton polarization to disentangle the contributions of hadronic and partonic origin to thermal radiation.
This work has been supported by VH-NG-823, HGS-HIRe, and the DFG through grant CRC-TR 211.
Keywords: dilepton; polarization; hadronic matter; QGP; virtual photon