Disentangling initial-state and evolution effects in heavy-ion collisions using EPOS and PHSD

In this study we examine the impact of the initial stage and dynamical evolution on final-state observables in heavy-ion collisions. For this goal we develop a novel approach, <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mi>EPOSir</a:mi> <a:mo>+</a:mo> <a:mi>PHSDe</a:mi> </a:mrow> </a:math> , which employs energy-conserving multiple parallel scattering approach, accommodating factorization and saturation (EPOS) initial conditions as the starting point for parton and hadron evolution within the parton-hadron-string dynamics (PHSD) microscopic transport approach. By examining the space-time evolution of matter in this model and comparing to EPOS (which starts with an <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:mi>S</b:mi> </b:mrow> </b:math> -matrix approach for parallel scatterings for the initial conditions and uses a hydrodynamic evolution for the quark-gluon plasma stage with the UrQMD as afterburner) and PHSD (which starts with primary high-energy <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:mi>N</c:mi> <c:mi>N</c:mi> </c:mrow> </c:math> scattering realized via the LUND string model and continues with fully microscopic transport dynamics for strongly interacting partonic and hadronic matter), we identify the key differences in the final particle distributions among the three approaches. Our analysis focuses on rapidity, transverse momentum spectra, and flow harmonics <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:msub> <d:mi>v</d:mi> <d:mn>2</d:mn> </d:msub> </d:math> for <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:mi>Au</e:mi> <e:mo>+</e:mo> <e:mi>Au</e:mi> </e:mrow> </e:math> collisions at the invariant energy of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mrow> <f:msqrt> <f:msub> <f:mi>s</f:mi> <f:mrow> <f:mi>N</f:mi> <f:mi>N</f:mi> </f:mrow> </f:msub> </f:msqrt> <f:mo>=</f:mo> <f:mn>200</f:mn> </f:mrow> </f:math> GeV. We find a dominant influence of dynamical evolution over the initial conditions on the final observables.