Speaker
Description
We investigate the $p_{\rm T}$-differential radial flow observable $v_0(p_{\rm T})$ in Au+Au collisions at $\sqrt{s_{\rm NN}} = 200$ GeV using AMPT model in its String Melting (SM) configuration. For inclusive charged hadrons, the AMPT-SM framework, that includes partonic dynamics, reproduces three hallmarks of genuine collective behavior: (i) long-range pseudorapidity correlations, (ii) factorization of two-particle correlations into a single-particle $v_0(p_{\rm T})$, and (iii) a centrality-independent scaling of the normalized shape $v_0(p_{\rm T})/v_0$ at low-$p_{\rm T}$, in close analogy with established signatures of anisotropic flow. For identified hadrons ($\pi^{\pm}$, $K^{\pm}$, $p + \bar{p}$), $v_0(p_{\rm T})$ exhibits a clear mass-ordering at low-$p_{\rm T}$ and a characteristic meson-baryon separation at intermediate-$p_{\rm T}$. In central Au+Au collisions, the NCQ-scaled observable $v_0(p_{\rm T})/n_q$ follows a universal curve when plotted against $(m_{\rm T} - m_0)/n_q$, while this scaling is progressively violated toward peripheral collisions where the partonic phase becomes short-lived. Taken together, these findings extend the paradigm of partonic collectivity from anisotropic to isotropic flow and establish radial collectivity as a partonic-stage phenomenon.