DREENA-C framework: joint R_AA and v₂ predictions and implications to QGP tomography

Abstract

In this paper, we presented our recently developed Dynamical Radiative and Elastic ENergy loss Approach (DREENA-C) framework, which is a fully optimized computational suppression procedure based on our state-of-the-art dynamical energy loss formalism in constant temperature finite size QCD medium. With this framework, we have generated, for the first time, joint R AA and v 2 predictions within our dynamical energy loss formalism. The predictions are generated for both light and heavy flavor probes, and different centrality regions in Pb + Pb collisions at the LHC, and compared with the available experimental data. While R AA predictions agree with experimental data, v 2 predictions qualitatively agree with, but are quantitatively visibly above, the experimental data (in disagreement with other models, which underestimate v 2). Consistently with numerical predictions, through simple analytic analysis, we show that R AA is insensitive to medium evolution (though highly sensitive to energy loss mechanisms), while v 2 is highly sensitive to the evolution. As a major consequence for precision quark-gluon plasma (QGP) tomography, this then leaves a possibility to calibrate energy loss models on R AA data, while using v 2 to constrain QGP parameters that are in agreement with both high and low p ⊥ data.

Multi-partonic medium induced cascades in expanding media

“…However, both the nPDF and VLE effects have clearly larger impact on this observable quantity. The path-length dependence of jet suppression can be studied using the jet v 2 evaluated in a simple approximation [65] as…”

Medium-induced cascade in expanding media

“…The path-length dependence of jet suppression can be studied using the jet v 2 evaluated in a simple approximation [57] as…”

Shape of the quark gluon plasma droplet reflected in the high- p⊥ data

“…The red line corresponds to the 0.57ς limit from Eq. (7), where ς is the anisotropy of the path lengths used in the DREENA-B calculations [7,10]. Importantly, for each centrality, the asymptotic regime -where the v 2 /(1 − R AA ) ratio does not depend on p ⊥ , but is determined by the geometry of the system -is already reached from p ⊥ ∼ 20-30 GeV; the asymptote corresponds to the analytically derived Eq.…”

“…Consequently, v 2 (angular differential suppression) carries information on both the spatial anisotropy and material properties that affect energy loss along a given path. On the other hand, R AA (angular average suppression) carries information only on material properties affecting the energy loss [7][8][9][10], so one might expect to extract information on the system anisotropy by taking a ratio of expressions which depend on v 2 and R AA . Of course, it is far from trivial whether such intuitive expectations hold, and what combination of v 2 and R AA one should take to extract the spatial anisotropy.…”