DREENA-B framework: First predictions of RAA and v2 within dynamical energy loss formalism in evolving QCD medium

• Main Authors: Dusan Zigic, Igor Salom, Jussi Auvinen, Marko Djordjevic, Magdalena Djordjevic
• Format: Article
• Language: English
• Published: Elsevier 2019-04-01
• Series: Physics Letters B
• Online Access: http://www.sciencedirect.com/science/article/pii/S0370269319301157

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 RAA and v2 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 v2 and RAA data. Such agreement is encouraging, i.e. may lead us closer to resolving v2 puzzle (difficulty of previous models to jointly explain RAA and v2 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 v2 predictions, RAA predictions remain robust and moreover in a good agreement with the experimental data; RAA 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 RAA and v2 - 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. Keywords: Relativistic heavy ion collisions, Quark-gluon plasma, LHC, Heavy flavor suppression, High pt hadrons