Quantum effects on a planetary scale The first neutrino oscillation measurement with KM3NeT/ORCA

KM3NeT/ORCA is a neutrino detector that is currently under construction in the Mediterranean Sea at 2.5km depth. This detector is designed to measure the fundamental particles called neutrinos, which are extremely hard to measure due to their low interaction probability with other matter. In this thesis the sensitivity of the detector is studied and optimised using simulated data, a time calibration method is applied and studied to check that the timing of the detector is around 1 ns precision, and finally, the first neutrino oscillation measurement is performed with this novel machine. Neutrino oscillations are a property of neutrinos that allows the particle to change from an initial flavour state to a different flavour state while it travels along a path. In the study performed here, the oscillating behaviour has been observed with a significance of 6.4 sigma versus the hypothesis that oscillations are not observed. The resulting values found for the parameters that describe these oscillations in the physical models match earlier found values by other experiments to a very good degree. Having this first successful detection of neutrino flavour oscillations paves the way towards more precise measurements of neutrino properties in the future, one of which is called the Neutrino Mass Ordering (NMO). Measuring the NMO is the ultimate goal of the ORCA detector. The NMO tells us which of the neutrino mass eigenstates is the heaviest, which is currently unknown.