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

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