Optimising methods and models for Galactic cosmic-ray data and their interpretation
Cosmic rays are high-energy charged particles that constantly reach the Earth from space. By studying their energy and composition, it is possible to learn how cosmic rays are accelerated in extreme astrophysical environments, how they propagate through the Galaxy, and whether they contain traces of new physics.
In her thesis, Marta Borchiellini first focuses on the search for antideuterons, extremely rare antimatter nuclei that are expected to be produced only in small amounts by known astrophysical processes. Their detection would therefore be a strong hint of exotic phenomena such as dark matter annihilation or decay. Using 12.5 years of data collected by the Alpha Magnetic Spectrometer (AMS-02), a precision particle detector on board the International Space Station, Borchiellini performs a systematic study of data-driven machine learning classifiers to develop a background rejection estimator specifically tailored for antideuteron identification.
Then, Borchiellini focuses on how cosmic rays propagate through the Galaxy, with particular attention to the role of electron-capture (EC) decay. She re-examines this process in light of recent high-precision measurements to assess its impact on cosmic-ray fluxes and to improve the reliability of propagation models. Although EC decay does not dominate cosmic-ray behaviour, its effects are found to be non-negligible for a few cosmic-ray isotopes, in particular (^{49})V, (^{51})Cr, and (^{57})Co.