Light nuclei and antinuclei production in proton-proton interactions

Abstract

Identifying the nature of dark matter is a major unsolved problem in physics. The detection of low-energy cosmic-ray antinuclei could provide a "smoking gun" signature of dark matter annihilation or decay, as they are produced essentially free of the astrophysical background. Such a detection could also indicate new astrophysical phenomena like undiscovered antimatter sources in our Galaxy. The main source of astrophysical antinuclei background are the interactions of cosmic-ray protons with hydrogen in the thin interstellar gas. However, their formation process is poorly understood. The impact of new-physics searches with cosmic-ray antinuclei can be increased by reducing uncertainties related to antinuclei formation modeling. For that purpose, this dissertation discusses how the coalescence mechanism for (anti)deuterons was extended to estimate the production of antihelium in cosmic-ray interactions. The results were used to model how antinuclei are transported in our Galaxy, to predict the antinuclei flux received at Earth. The production mechanism of light antinuclei have been studied in accelerator-based experiments before. However, very few proton-proton measurements exist at energies which are relevant for cosmic-ray antinuclei production. Modeling of antinuclei formation also requires high-precision measurements of antiproton production. These factors motivate the analysis of new large p-p data sets from modern particle accelerator experiments. NA61/SHINE is a fixed-target experiment at the CERN-SPS, which studies hadron-nucleus and nucleus-nucleus collisions for various physics goals. This dissertation presents new measurements of proton, antiproton, as well as pion and kaon spectra, using the high-statistics p-p data from NA61/SHINE. The new results significantly extend the phase space coverage in rapidity and transverse momentum, as compared to previous results. They also dramatically reduce uncertainties in antiproton production. The first measurements of deuteron production at energies relevant for cosmic-ray studies are presented. The viability of measuring antideuteron production and two-particle angular correlations, with the recently-upgraded NA61/SHINE detector, is also shown.