Comparison of pair-source and correlation-function based Lévy analyses in Ar+Sc system at SPS energies

Abstract

Non-Gaussian features in femtoscopic observables have been observed in high-energy collisions, yet their origin remains not fully understood. This study focuses on the phenomenological approach to femtoscopy, going beyond the Gaussian approximation by utilizing Lévy-stable source distributions. Using UrQMD simulations, three-dimensional analyses of pion sources are done in central Ar+Sc collisions, and the extracted parameters are studied as functions of transverse mass and collision energy. This analysis contributes to a hadronic baseline motivated by past and future research work in femtoscopy at the NA61/SHINE experiment. A direct methodological comparison is presented between parameters extracted from the projections of three-dimensional pair-source distribution and those obtained from the three-dimensional correlation function, reconstructed via Fast Fourier Transform.

Comments: 12 pages, 7 figures, proceedings of the 18th Workshop on Particle Correlations and Femtoscopy (WPCF 2026), Budapest, Hungary, May 18 - 22, 2026, to be submitted to the International Journal of Modern Physics A, Thematic Issue on Paritcle Correlations and Femtoscopy