March 3, 2026Open Access

Effect of transport processes on elliptic flow centrality dependence under different initial conditions in the AMPT model

Key Points

Elliptic flow is amplified in central collisions primarily by partonic viscosity, showing a distinct dependence on transport processes.
In peripheral collisions, increases in hadronic viscosity significantly enhance elliptic flow, aligning better with experimental STAR data.
Analysis using the AMPT model reveals varying roles of partonic and hadronic transport processes across collision centralities.
Initial pressure gradients impact elliptic flow, indicating complex dependencies on model parameters in collision dynamics.

Abstract

Abstract Using the AMPT model, we study charged hadron elliptic flow (v₂ v 2) centrality dependence in Au+Au collisions at s₍₍=200~GeV s NN = 200 GeV. We find distinct centrality-dependent roles for partonic (₏ σ p) and hadronic (₇ σ H) transport processes. In central collisions, v₂ v 2 is dominantly amplified by larger ₏ σ p (reducing partonic viscosity) but insensitive to ₇ σ H. In peripheral collisions, larger ₇ σ H (reducing hadronic viscosity) significantly enhances v₂ v 2, flattening its centrality dependence and improving agreement with STAR data. Initial pressure gradients (enhanced by Lund parameter a₋ a L) also increase v₂ v 2, while b₋ b L affects spectra but not flow. This centrality-differential sensitivity to ₏ σ p and ₇ σ H provides a novel strategy for extracting phase-specific shear viscosities.

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Zhang et al. (Wed,) studied this question.

synapsesocial.com/papers/69a75d06c6e9836116a266ab https://doi.org/https://doi.org/10.1140/epjc/s10052-026-15334-7

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