The NOvA experiment is a neutrino oscillation experiment designed to make precise measurements of ν e andν e appearance and ν µ andν µ disappearance at long distances and GeV energy scales. Using Fermilab's Neutrinos at the Main Injector (NuMI) beam, the experiment is provided with a highly pure and abundant source of either ν µ orν µ . NOvA's ν µ andν µ disappearance measurement is particularly sensitive to constraining the sin 2 θ 23 vs. ∆m 2 32 space of oscillation parameters. Any difference

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... between ν µ andν µ disappearance in vacuum could be an indication of the combination of Charge Conjugation, Parity and Time reversal (CPT) symmetry not being conserved in the neutrino sector or something else beyond our current understanding of physics. This thesis presents results from two ν µ andν µ disappearance analyses, one where sin 2 θ 23 and ∆m 2 32 are assumed to be identical as in the standard three neutrino flavour model, and the other where the oscillation parameters can differ between neutrinos and antineutrinos. In the later, the core analysis of this thesis, the parameters sin 2 θ 23 and ∆m 2 32 are measured using just the information from neutrinos, and the parameters sin 2θ 23 and ∆m 2 32 are measured using just the information from antineutrinos. The results for the mass splitting are ∆m 2 32 = 2.48 +0.07 −0.09 × 10 −3 eV 2 and ∆m 2 32 = 2.55 +0.12 −0.13 × 10 −3 eV 2 . The results for the mixing angle are sin 2 θ 23 = 0.51 in the range [0.45, 0.57], and two degenerate best fits for sin 2θ 23 at 0.41 and 0.61 in the ranges [0.38, 0.45] and [0.57, 0.64] allowed at 1 σ. No significant difference between the oscillation parameters measured using ν µ orν µ was found. The data analysed in this thesis was collected between 2014 and 2019, for which the NOvA detectors collected an exposure of 8.85 × 10 20 and 12.33 × 10 20 protons-on-target (POT) for the production of the ν µ andν µ beams respectively. This data is about a quarter and a third of what NOvA is expected to collect in ν andν mode, respectively.