Initial partonic eccentricity fluctuations in a multi-phase transport model

TL;DR

This study investigates initial partonic eccentricities and their fluctuations in Au+Au collisions at 200 GeV using a multi-phase transport model, analyzing harmonic orders, cumulant definitions, and their relation to flow harmonics.

Contribution

It systematically compares participant and cumulant eccentricities, explores their ratios and conversion coefficients, and examines dependencies on transverse momentum and pseudo-rapidity.

Findings

Cumulant eccentricities differ from participant definitions.

Ratios of cumulant eccentricities relate to flow harmonic ratios.

Eccentricity fluctuations depend on transverse momentum and pseudo-rapidity.

Abstract

Initial partonic eccentricities in Au+Au collisions at center-of-mass energy $\sqrt{s_{NN}}$ = 200 GeV are investigated using a multi-phase transport model with string melting scenario. The initial eccentricities in different order of harmonics are studied using participant and cumulant definitions. Eccentricity in terms of second-, fourth- and sixth order cumulants as a function of number of participant nucleons are compared systematically with the traditional participant definition. The ratio of the cumulant eccentricities $\varepsilon\left\{4\right\}/\varepsilon\left\{2\right\}$ and $\varepsilon\left\{6\right\}/\varepsilon\left\{4\right\}$ are studied in comparison with the ratio of the corresponding flow harmonics. The conversion coefficients ($v_n/\varepsilon_n$) are explored up to fourth order harmonic based on cumulant method. Furthermore, studies on transverse momentum ($p_T$) and pseudo-rapidity ($\eta$) dependencies of eccentricities and their fluctuations are presented. As in ideal hydrodynamics initial eccentricities are expected to be closely related to the final flow harmonics in relativistic heavy-ion collisions, studies of the fluctuating initial condition in the AMPT model will shed light on the tomography properties of the initial source geometry.