Harmonic flow correlations in Au+Au reactions at 1.23 AGeV: A new testing ground for the Equation-of-State and expansion geometry

Abstract

Correlations between the harmonic flow coefficients v1, v2, v3 and v4 of nucleons in semi-peripheral Au+Au collisions at a beam energy of 1.23 AGeV are investigated within the hadronic transport approach Ultra-relativistic Quantum Molecular Dynamics (UrQMD). In contrast to ultra-relativistic collision energies (where the flow coefficients are evaluated with respect to the respective event plane), we predict strong correlations between the flow harmonics with respect to the reaction plane. Based on an event-by-event selection of the midrapidity final state elliptic flow of protons we show that as a function of rapidity, I) the sign of the triangular flow changes, II) that the shape of v4 changes from convex to concave, and III) that v3 ∝ v1v2 and v4 ∝ v 2 2 for all different event classes, indicating strong correlations between all investigated harmonic flow coefficients.