Thermalization time constrained by high-$p_\perp$ QGP tomography

Stefan Stojku, Jussi Auvinen, Marko Djordjevic, Pasi Huovinen, Magdalena Djordjevic

Published 2020-08-20Version 1

We show that high-$p_\perp$ $R_{\mathrm{AA}}$ and $v_2$ are way more sensitive to the QGP thermalization time, $\tau_0$, than the distributions of low-$p_\perp$ particles, and that the high-$p_\perp$ observables prefer relatively late thermalization at $\tau_0 \sim 1$ fm/$c$. To calculate high-$p_\perp$ $R_{\mathrm{AA}}$ and $v_2$, we employ our newly developed DREENA-A formalism, which combines state-of-the-art dynamical energy loss model with 3+1-dimensional hydrodynamical simulations. The model applies to both light and heavy flavor, and we predict a larger sensitivity of heavy observables to the thermalization time. Elliptic flow parameter $v_2$ is also more sensitive to $\tau_0$ than $R_{\mathrm{AA}}$ due to non-trivial differences in the evolution of in-plane and out-of-plane temperature profiles. This presents, to our knowledge, the first example of applying QGP tomography to constrain bulk QGP observables with high-$p_\perp$ observables and related theory.