Femtoscopic study of the proton-proton and proton-deuteron systems in heavy-ion collisions at the LHC

Abstract

This work reports femtoscopic correlations of p-−p(p‾-−p‾) and p−−d(p‾-−d‾) pairs measured in Pb–Pb collisions at center-of-mass energy per nucleon s<inf>NN</inf> = 5.02 TeV in the ALICE Collaboration. A fit to the measured proton-proton correlation functions allows one to extract the dependence of the nucleon femtoscopic radius of the particle-emitting source on the pair transverse mass (m<inf>T</inf>) and on the average charge particle multiplicity 〈dNch/dη〉1/3 for three centrality intervals (0–10%,10−−30%,30−−50%). In both cases, the expected power-law and linear scalings are observed, respectively. The measured p–d correlations can be described by both two- and three-body calculations, indicating that the femtoscopy observable is not sensitive to the short-distance features of the dynamics of the p-(p-n) system, due to the large inter-particle distances in Pb–Pb collisions at the LHC. Indeed, in this study, the minimum measured femtoscopic source sizes for protons and deuterons have a minimum value at 2.73<inf>−0.05</inf>+0.05 and 3.10<inf>−0.86</inf>+1.04 fm, respectively, for the 30–50% centrality collisions. Moreover, the m <inf>T</inf>-scaling obtained for the p–p and p–d systems is compatible within 1 σ of the uncertainties. These findings provide new input for fundamental studies on the production of light (anti)nuclei under extreme conditions. © 2025 The Authors.