Source shapes in coordinate and momentum space in $\sqrt{s_\text{NN}}$ = 200 GeV Au+Au collisions

Abstract

In high-energy heavy-ion physics, femtoscopy aims to explore and understand the space-time characteristics of the collisions through investigating the correlation function of particle pairs. In recent years, experimental measurements have shown that the shape of the particle source function can be well described by the Lévy distribution, motivating further phenomenological studies. In this work, we perform a three-dimensional analysis of the source shapes for different particle-pair types in $\sqrt{s_\text{NN}}=200$ GeV Au+Au collisions generated with the EPOS event generator. In contrast to our previous analyses, where we fitted the one-dimensional projections of the pair distribution function, $D(ρ_j)$ ($j \in \{\text{out}, \text{side}, \text{long}\}$), now we reconstruct the three-dimensional $C(\boldsymbol{q})$ correlation function and fit it directly, as in experimental analyses. Furthermore, we now apply full three-dimensional fits instead of fitting the one-dimensional projections. We find that this approach results in smaller Lévy index values, while the direction averaged Lévy scale and the correlation strength remain largely unchanged, except for kaons. In the case of pions, the $α$ values are closer to the PHENIX data, showing a good agreement above 20\% centrality.