DREENA-B framework: First predictions of R <inf>AA</inf> and v <inf>2</inf> within dynamical energy loss formalism in evolving QCD medium

Abstract

© 2019 The Author(s) Dynamical energy loss formalism allows generating state-of-the-art suppression predictions in finite size QCD medium, employing a sophisticated model of high-p ⊥ parton interactions with QGP. We here report a major step of introducing medium evolution in the formalism though 1+1D Bjorken (“B”) expansion, while preserving all complex features of the original dynamical energy loss framework. We use this framework to provide joint R AA and v 2 predictions, for the first time within the dynamical energy loss formalism in evolving QCD medium. The predictions are generated for a wide range of high p ⊥ observables, i.e. for all types of probes (both light and heavy) and for all centrality regions in both Pb+Pb and Xe+Xe collisions at the LHC. Where experimental data are available, DREENA-B framework leads to a good joint agreement with v 2 and R AA data. Such agreement is encouraging, i.e. may lead us closer to resolving v 2 puzzle (difficulty of previous models to jointly explain R AA and v 2 data), though this still remains to be thoroughly tested by including state-of-the-art medium evolution within DREENA framework. While introducing medium evolution significantly changes v 2 predictions, R AA predictions remain robust and moreover in a good agreement with the experimental data; R AA observable is therefore suitable for calibrating parton-medium interaction model, independently from the medium evolution. Finally, for heavy flavor, we observe a strikingly similar signature of the dead-cone effect on both R AA and v 2 - we also provide a simple analytical understanding behind this result. Overall, the results presented here indicate that DREENA framework is a reliable tool for QGP tomography.