CERN Accelerating science

This thesis concentrates on two main research topics. Firstly, it explores the strong interaction within a system of three nucleons. This is done by measuring effective two-body correlations through the femtoscopy technique with proton and deuteron pairs. Secondly, it investigates the production of light nuclei in proton-proton collisions.$\\$ Two-particle momentum correlations using the femtoscopy technique have opened up new avenues for studying interactions between hadrons, including those involving strange and charm hadrons. As a natural progression, the investigation of three-body systems has emerged. The momentum correlation between protons and deuterons offers a valuable means to explore the strong interaction among three nucleons. These systems play a crucial role in nuclear physics, as their properties can help constrain nuclear interactions, leading to a deeper understanding of the nuclear structure and the equation-of-state of dense nuclear matter.$\\$ This work presents the first measurement and interpretation of the momentum space correlation between protons and deuterons (p-d) in proton-proton (pp) collisions at the LHC using ALICE. The observed signal in the correlation function cannot be adequately explained by effective two-body calculations treating protons and deuterons as point-like and distinguishable particles produced at short distances. These calculations only consider the Coulomb and strong nuclear interactions based on the measured scattering parameters from p-d scattering experiments. To properly interpret the p-d correlation, comprehensive three-body calculations were performed for the first time and applied in this analysis. These calculations appropriately account for the deuteron's internal structure, the dynamics of three nucleons when the proton and deuteron are close in phase-space, and all relevant partial waves. Additionally, the three-body calculations consider quantum statistical effects and the short-range part of the strong interaction. The fact that the measured p-d correlation can only be described by these three-body calculations suggests that nucleons explicitly play a role in the correlation between the hadron and the light nuclei at the LHC. Moreover, the measurements demonstrate the feasibility of studying interactions in a three-hadron system by investigating deuteron-hadron correlations. Such measurements will provide access to the isospin-dependent strong interaction and have the potential to explore the effects of genuine many-body interactions at the LHC in the future.$\\\\$ In collision experiments, the production of light (anti-)nuclei is observed. However, the microscopic understanding of their production is still intensely debated. This is particularly true for light nuclei, which have a binding energy per nucleon of approximately 2 MeV, significantly lower than the chemical freeze-out temperature ($T_\mathrm{c}\sim155$ MeV). Two models, the Statistical Hadronization Model and the Coalescence Model, are commonly used to study the production yield of light nuclei. This work focuses on the latter, specifically concerning the lightest (anti-)nuclei, the (anti-)deuterons. For the first time, the calculation of the coalescence parameter $\mathcal{B}_2$, which is related to the production probability, is extended to incorporate realistic deuteron wavefunctions based on Chiral Effective Field Theory ($\chi$EFT). The study also investigates the differential behavior of $\mathcal{B}_2$ with respect to transverse momentum $p_\mathrm{T}$. To predict $\mathcal{B}_2$ as a function of $p_\mathrm{T}$, the calculation incorporates the femtoscopic source size of emitted nucleons, measured in pp collisions at $\sqrt{s}=13$ TeV. The computed $\mathcal{B}_2$ successfully captures the observed slope in the measurements and is found to be sensitive to the choice of the deuteron wavefunction.$\\\\$ Furthermore, this work calculates the deuteron formation probability using the Wigner formalism, which is a crucial input for modeling a new coalescence afterburner for event generators. The calculation is performed for four choices of the deuteron wavefunction, each reflecting the nuclear interaction between the pair of nucleons forming the deuteron. The predicted deuteron spectra in the event generators exhibit clear sensitivity to the chosen deuteron wavefunction, with the Argonne $v_{18}$ and $\chi$EFT wavefunctions providing the most accurate description of the deuteron yield in pp collisions at $\sqrt{s}=13$ TeV