Abstract: In the last decades, femtoscopic measurements from heavy-ion collisions have become a popular tool to investigate the strong interactions between hadrons. The key observables measured in such experiments are the two-hadron momentum correlations, which depend on the production mechanism of hadron pairs and the final-state interactions. Given the complexity of ultra-relativistic collision experiments, the source term describing the production mechanism can only be modeled phenomenologically based on numerous assumptions. The commonly employed approach for analyzing femtoscopic data relies on the Koonin-Pratt formula, which relates the measured correlation functions with the relative wave function of an outgoing hadron pair and a source term that is assumed to be universal. Here, I critically examine this universality assumption and show that for strongly interacting particles such as nucleons, the interpretation of femtoscopic measurements suffers from a potentially large intrinsic uncertainty. I also comment on the ongoing efforts to explore three-body interactions using this experimental technique.
About the speaker: Prof. Dr. Dr.h.c. Ulf-G. MeiBner is a full professor in theoretical physics and the leader of the theory group of the Helmholtz Institute for Radiation and Nuclear Physics at Bonn University. He is a renowned strong interaction physicist. Being the leader of a world-leading team on theoretical nuclear and hadron physics, he is director at the Institute for Advanced Simulation-4 (IAS-4) at the Jülich Research Center. He was the dean of the Faculty of Natural Sciences and Mathematics, Bonn University, from 2008 to 2016. Since 2024, he has been a chief scientist at the Peng Huanwu Collaborative Center for Research and Education, International Institute for Interdisciplinary and Frontiers, Beihang University. Here are a few among the many awards and honors he received: ERC Advanced Grant (2021), CAS President's Fellowship for Distinguished Scientists (2018, 2025), Lise-Meitner Prize of the European Physical Society (2016), member of Academia Europaea (2010), Fellow of the American Physical Society (2009). He was also the Spokesperson of the Sino-German Collaborative Research Center CRC110. He has published more than 750 papers with a total citation of more than 82000 and an h-index 117