Initial partonic eccentricities in $\text{Au}+\text{Au}$ collisions at center-of-mass energy $\sqrt{s_{NN}}=200$ GeV are investigated by using a multiphase transport model with a string-melting scenario. The initial eccentricities in different order of harmonics are studied by 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 harmonics based on the cumulant method. Furthermore, studies on transverse momentum ($p_T$) and pseudorapidity ($\eta$) 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.

• Received 28 June 2016
• Revised 1 October 2016

DOI:https://doi.org/10.1103/PhysRevC.94.044915