Speaker: Dr. Oscar Garcia Montero (Universität Bielefeld)
Title of Talk:  Enhancement of photon momentum anisotropies during the late stages of relativistic heavy-ion collisions

Abstract:
During heavy ion collisions (HICs) a medium of strongly interacting
degrees of freedom is formed, the so-called Quark Gluon Plasma (QGP).
Electromagnetic probes are produced during these events, but since they
do not interact strongly, they escape virtually unscathed, carrying the
information of the space-time evolution of this medium. However, we
still do not fully understand their mechanisms of productions, which
limits our capability for modeling, and therefore the extraction of such
information.

In this talk I will address our inability to explain with our HIC models
both the total yield and the anisotropy of the excess electromagnetic
probes created by the medium (as opposed to i.e. hadronic decay). These
selection of EM probes are commonly referred as _direct, _and hence the
name. I will show how a significant increase of anisotropy in the
calculated momentum anisotropies can arise due to microscopic
non-equilibrium dynamics during the hadronic stages of the HIC events.
This enhancement is found in comparison to standard calculations, which
rely on the folding of equilibrium rates to a hydrodynamical evolution.
Once combined with photons produced above the particlization temperature
in the hydrodynamical evolution, the differences between the two
approaches are modest regarding p_\perp-differential spectra, but are
clearly noticeable at low p_\perp for the elliptic flow: non-equilibrium
dynamics enhance the photon v_2 below p_\perp < 1.5 GeV.

Venue (HYBRID-EVENT): Goldene Box, Physikalisches Institut, INF 226, 69120 Heidelberg AND all talks will also be streamed via the permanent Zoom-link:

https://zoom.us/j/94602401603?pwd=SVRYMHQxaWJrUGtFWXRWdkFaKzJVUT09
Meeting ID: 946 0240 1603
Passcode: 386993

The seminar will take place in presence in accordance with the current COVID-19 regulations for on-site events (Please wear a FFP2 mask or surgical mask if the minimum distance of 1.5m can not be guaranteed).