Speaker
Description
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, the polarization observables of thermal virtual photons as a function of mass and momentum will be presented. To connect to the experiment, we discuss the modeling of the underlying medium evolution of heavy-ion collisions in the few GeV energy regime via coarse-grained transport simulations. The polarization results obtained within our framework are compared to existing measurements from HADES and NA60, and predictions for upcoming HADES data will be provided. Finally, we address the prospects of using dilepton polarization to disentangle the contributions of hadronic and partonic origin to thermal radiation.
| Category | Theory |
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