The KM3NeT experiment: methods for time, position and pointing calibration of the detector

Neutrino astronomy is an emerging field in astroparticle physics, focused on measuring astrophysical neutrino fluxes and identifying their sources to better understand cosmic ray origins and acceleration mechanisms. Neutrinos, due to their lack of electric charge and since they interact solely via the Weak interaction, can travel vast distances across the Universe without being absorbed or deflected by magnetic fields, making them ideal probes of high-energy astrophysical phenomena. Their detection is achieved by neutrino telescopes, placed deep underwater or under ice. Since the early precursors, started in the 1970s, significant progresses have been made and the second generation of detectors is now being deployed. The development of this thesis has been carried out within the KM3NeT experiment, which consists in two underwater detectors, KM3NeT/ARCA and KM3NeT/ORCA, under installation and taking data in the depths of the Mediterranean Sea. Recently, the KM3NeT Collaboration has announced the detection with KM3NeT/ARCA of KM3- 230213A, the most energetic cosmic neutrino observed so far, demonstrating the capabilities of the detector even in a partial configuration. At completion, the two detectors are going to reach an overall volume greater than 1 km3 of sea water instrumented with thousands of optical sensors arranged in vertical strings. To reach the desired performances in terms of angular resolution on the reconstructed direction of neutrinos, the calibration of the detector plays a crucial role. The key parameters to optimize in order to improve the angular resolution are the time synchronization of the optical sensors and the precise determination of their position. Moreover, the correct pointing of the detector and the evaluation of its accuracy is pivotal in order to search for point-like neutrino sources. This thesis presents methods for timing, position, and pointing calibration of the detector, crucial to achieve the scientific goals of the KM3NeT experiment.