Verify NCQ scaling restoration above 4 GeV in Au+Au collisions

Determine whether the Number of Constituent Quarks (NCQ) scaling of elliptic flow v2 reappears as the center-of-mass energy per nucleon pair sqrt(sNN) in Au+Au collisions increases beyond 4 GeV, thereby confirming the resurgence of partonic interactions and the gradual onset of partonic collectivity at intermediate energies.

Background

The paper discusses elliptic flow (v2) and Number of Constituent Quarks (NCQ) scaling as indicators of partonic collectivity and quark-gluon plasma formation. While NCQ scaling is robust at higher energies (e.g., RHIC and LHC), STAR data at sqrt(sNN)=3 GeV show a breakdown of NCQ scaling, suggesting a hadronic-dominated regime at low energies.

Motivated by this, the authors posit that as collision energy increases beyond approximately 4 GeV in Au+Au collisions, NCQ scaling may gradually reappear, signaling the resurgence of partonic interactions. They explicitly note that this expectation is a theoretical conjecture pending experimental verification, framing it as an open question within the Beam Energy Scan program.