What question did this study set out to answer?

This work aims to investigate higher flow harmonics in Au-Au collisions at various beam energies using the HYDJET++ simulation.

February 5, 2026

Higher harmonics of anisotropic flow at RHIC Beam Energy Scan energies

Key Points

This work aims to investigate higher flow harmonics in Au-Au collisions at various beam energies using the HYDJET++ simulation.
Conducted HYDJET++ simulations for flow harmonics at beam energies ranging from 14.5 GeV to 200 GeV.
Calculated elliptic, triangular, quadrangular, and pentangular flow based on eccentricities and rapidity profile modulations.
Analyzed correlations between modulation parameters and flow harmonics to identify differences in their behavior.
Observed a linear correlation of v3 with rapidity modulations, while v3's eccentricity showed a non-linear trend.
No background effects for v5 and distinct behaviors of v4 were noted linked to v2's reaction plane.
Predicted v5 of charged hadrons at remaining energies based on a constant parameter a5, which remained independent of beam energy.

Abstract

In this work, we report the HYDJET++ simulation results for the higher flow harmonics like elliptic flow (v2), triangular flow (v3), quadrangular flow (v4), and pentangular flow (v5) in Au-Au collisions at 200 GeV, 62. 4 GeV, 39 GeV, 27 GeV, 19. 6 GeV, and 14. 5 GeV. The higher harmonics were calculated based on the eccentricities ϵn and modulation in the rapidity profile ρn of the fireball. These parameters were treated as related to the impact parameter. Both approaches describe the data with some qualitative differences. The ρ3 modulations show a linear correlation with v3 while the ϵ3 show a non-linear trend. A background v4 was observed due to v2 in its reaction plane while no such background was observed in the symmetry plane of v3, and no background effects were observed for v5. The constant a5, which defines the strength of the pentangular modulation at a given impact parameter, was found to be independent of beam energy, hence, we predicted the v5 of charged hadrons for the remaining energies using a₅=0. 025. Finally, we have discussed the effect of these harmonics in the final state distribution of charged hadrons.

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