Unveiling the fundamental production mechanism of light nuclei using coalescence and femtoscopy

Light (anti)nuclei are of significant interest in nuclear and astroparticle physics, with implications ranging from fundamental hadron-hadron interactions to indirect Dark Matter searches. In the context of Dark Matter, a precise understanding of their formation mechanism is crucial for interpreting results from experiments such as GAPS and AMS-02. This thesis aims to definitively determine how light nuclei are formed. Historically, two principal models—the Statistical Hadronization Model and the Coalescence Model—have been tested by comparing their nuclear yield predictions with experimental data. However, the diversity of their implementations has prevented a clear consensus. Here, a model-independent approach is introduced through femtoscopy, which investigates nuclear formation by analyzing momentum correlations between pions and deuterons. The detection of a distinct ∆ resonance decay signature indicates that deuterons, and by extension all light nuclei, are produced via final state interactions occurring during or after the decay of short-lived resonances. Simple causality arguments thereby rule out thermal production mechanisms. Building on these insights, a sophisticated coalescence model based on the Wigner Function Formalism is developed. When tested using the EPOS 3 event generator, the model successfully reproduces the deuteron spectra measured by the ALICE collaboration without introducing free parameters—provided that experimental inputs such as multiplicity, momentum distributions, emission source sizes, and nuclear wave functions are used. This model is further encapsulated within a custom Monte Carlo generator, ToMCCA, which extends predictions across the full energy and multiplicity range explored at the LHC with significantly improved statistical precision. Moreover, the coalescence approach is extended to A=3 (hyper)nuclei, including 3He, 3H, and 3ΛH, marking the first event-by-event predictions that utilize realistic nuclear wave functions. Overall, this work establishes a robust baseline for nuclear flux predictions by substantially reducing model uncertainties, thereby providing a solid foundation for future searches for new physics.