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

TL;DR

This study measures femtoscopic correlations of proton-proton and proton-deuteron pairs in Pb-Pb collisions at 5.02 TeV, revealing source size dependencies and scaling behaviors relevant for understanding light nuclei production in heavy-ion collisions.

Contribution

It provides the first detailed femtoscopic analysis of p-p and p-d systems at LHC energies, including source size scaling and correlation modeling insights.

Findings

Observed power-law and linear scaling of source sizes with multiplicity and transverse mass.

Minimum source sizes for protons and deuterons are approximately 2.73 fm and 3.10 fm.

Femtoscopic size scaling is consistent within uncertainties for p-p and p-d systems.

Abstract

This work reports femtoscopic correlations of p$-$p ($\bar{\rm p}-\bar{\rm p}$) and p$-$d ($\bar{\rm p}-\bar{\rm d}$) pairs measured in Pb$-$Pb collisions at center-of-mass energy per nucleon $\sqrt{s_{\rm NN}}$ = 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 ($m_\text{T}$) and on the average charge particle multiplicity $\langle\text{dN}_\text{ch}/\text{d}\eta\rangle^{1/3}$ 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 $2.73^{+0.05}_{-0.05}$ and $3.10^{+1.04}_{-0.86}$ fm, respectively, for the 30$-$50$\%$ centrality collisions. Moreover, the $m_{\rm{T}}$-scaling obtained for the p$-$p and p$-$d systems is compatible within 1$\sigma$ of the uncertainties. These findings provide new input for fundamental studies on the production of light (anti)nuclei under extreme conditions.