Speaker
Description
Because photons and dileptons are unlikely to interact after production within a quark-gluon plasma (QGP), they can probe the inner dynamics of this strongly interacting system. To leading order in the electromagnetic coupling and all orders in the strong coupling, the observable emission rates can be determined from the QCD vector channel spectral function. The resummed next-to-leading order (NLO) spectral function is intimately related to the Euclidean correlator, which can be estimated from continuum-extrapolated lattice data [1]. We report on two aspects of our theoretical investigation: i) we embed derived NLO dilepton rates (at $\mu_B = 0$) in viscous, relativistic hydrodynamical simulations of heavy ion collisions and focus our analysis on the invariant mass region $1 < M < 3$ GeV where QGP manifestations are expected to be prevalent, and ii) we generalize the perturbative calculation to non-zero baryon chemical potential $\mu_B$. In the first part, we show results for dilepton measurements at RHIC and LHC energies. In the second part, we report that the presence of $\mu_B$ not only modifies the quark distribution in the QGP, but also the thermal masses that control the necessary screening effects. While the latter has been examined for real photons [2], we present new results away from the light cone. This involves properly understanding how $\mu_B$ enters the strict NLO computation, the so-called LPM effect (at low invariant masses), and how to smoothly interpolate between the two regimes as originally advocated in Ref. [3]. These results enable predictions to be made for low-energy heavy ion experiments that will explore QGPs with net baryon content.
[1] G. Jackson and M. Laine, "Testing thermal photon and dilepton rates," JHEP 11, 144 (2019)
[2] H. Gervais and S. Jeon, "Photon Production from a quark-gluon-plasma at finite baryon chemical potential," Phys. Rev. C86, 034904 (2012)
[3] I. Ghisoiu and M. Laine, "Interpolation of hard and soft dilepton rates," JHEP 10, 083 (2014)
