Study of neutrino oscillations at the NOvA experiment

NOvA is a two detector long-baseline neutrino oscillation experiment using Fermilab's 700 kW NuMI neutrino beam. It studies the disappearance of muon (anti)neutrinos and the appearance of electron (anti)neutrinos in the beam over a distance of 810 km be- tween the detectors. This thesis presents the latest 2020 update of the NOvA neutrino oscillation analysis within the standard model of three neutrinos mixing. With about +50% new data in NuMI neutrino mode (+22% of the total available data) and nu- merous analysis upgrades compared to the previously reported results, the experiment has made over 4σ-significant observation of electron antineutrino appearance in muon antineutrino beam and constrained the oscillation parameters |∆m2 32|, sin2 θ23 and δCP. The text closely depicts the analysis and all its novelties and changes. A detailed inspec- tion is dedicated to the systematic uncertainties and their estimation and validation. Although statistical uncertainties currently dominate in these measurements, under- standing the major sources of systematic uncertainties and their correlations is vital for both the interpretation and precision of the results and for further improvements of the analysis.