Measurement of (anti)helium production in pp collisions with ALICE at the LHC

The formation of light (anti)nuclei in high-energy hadronic collisions remains an open question under active theoretical and experimental investigation. An equal amount of matter and antimatter is produced at the LHC energies, enabling the investigation of (anti)nuclei formation mechanisms across several collision systems. However, with respect to simple nucleons, production rates for bound states are suppressed by about a factor 1000 in small systems for every added nucleon. For this reason, the currently available measurements are limited by large statistical uncertainties and poor granularity, warranting new studies focusing on the heavier states as helium-3 and antihelium-3, a fundamental proving ground to test statistical hadronisation and coalescence models. This work discusses the production of (anti)helium-3 in pp collisions at √s = 13.6 TeV. The measurement is carried out using data collected by ALICE in 2022, using the first pp collisions of the Run 3 of LHC. Thanks to this wealth of data, the yield of helium-3 and antihelium-3 is measured with unprecedented granularity, improving on the statistical precision with respect to results in literature by more than a factor 10. The challenges faced for the measurement with the new ALICE detector are detailed in this thesis. The results of this thesis contribute to clarifying the formation mechanisms of light antinuclei, providing a precise constrain for production models, paving the road for future measurements that will, in the longer term, be used as input to the modelling for the production of cosmic antinuclei for indirect dark matter searches.