[CANCELLED] Untangling the evolution of heavy ion collisions using direct photon interferometry

by Oscar Garcia Montero (Karl-Ruprechts-Universität Heidelberg)

Monday 9 Mar 2020, 15:00 → 16:00 Europe/Zurich

We investigate the measurement of Hanbury Brown-Twiss (HBT) photon correlations an experimental tool todiscriminate different sources of photon enhancement, which have been proposed to simultaneously reproduce the direct photon yield and the azimuthal anisotropy measured in nuclear collisions at RHIC and the LHC. To showcase that HBT correlations can distinguish between different photon sources, we consider two different scenarios in which we enhance the yields from standard hydrodynamical simulations. In the first, additional photons are produced from the early pre-equilibrium stage computed from the ''bottom-up" thermalization scenario. In the second, the thermal rates are enhanced close to thepseudo-critical temperature $T_c\approx 155\,\text{MeV}$ using a phenomenological ansatz. We compute the correlators in terms of the relative momentum of the photon pair, that the beam (longitudinal) direction is the most sensitive to different photon sources. Finally, we study the feasibility of measuring a direct photon HBT signal in the upcoming high-luminosity LHC runs. Considering only statistical uncertainties, we find that with the projected $\sim 10^{10}$ heavy ion events a measurement of the HBT correlations for $K_\perp<1\, \text{GeV}$ is statistically significant.