PHENIX Measurements of Azimuthal Anisotropy for $\pi^0$ Production at High $p_T$ in Au+Au Collisions at $\sqrt{s_{NN}}=200$GeV

TL;DR

This paper presents precise measurements of azimuthal anisotropy for neutral pion production at high transverse momentum in gold-gold collisions, revealing discrepancies with existing models and suggesting the importance of non-perturbative effects in jet-medium interactions.

Contribution

It provides improved $v_2$ measurements over a broad $p_T$ range and combines them with $R_{AA}$ to challenge current pQCD energy loss models, indicating the need for new theoretical approaches.

Findings

Current pQCD models cannot fully explain $ o$ suppression patterns.

Results highlight potential significance of non-perturbative effects.

Data may resolve discrepancies in predicted transport coefficients.

Abstract

An improved measurement of $v_2$ for $\pi^0$ in a broad range of $p_T$ and centrality is presented. By combining $v_2$ with the $R_{AA}$, we provide new insights on jet-medium interactions. We show that current pQCD energy loss models cannot describe the suppression of the $\pi^0$ as a function of the angle with respect to the reaction plane. Our result could help to resolve the factor of 4 differences in the predicted transport coefficients among these models. Alternatively, it may suggest that non-perturbative effects associated with the strongly coupled QGP are important, and new theoretical developments are needed to fully understand the jet medium interactions.