A search for neutron-antineutron oscillation in the NOvA experiment

This dissertation presents the search of neutron-antineutron oscillation using the data collected in the Far Detector of the NOvA experiment. Searching for neutron anti-neutron oscillation is becoming an active research direction that promises immense values for field of particle physics and cosmology. An experimental observation of the phenomenon would offer the possibility of new physics associated with anomalous B and/or B-L violating processes. This work is opening with a general introduction of the neutron-antineutron oscillation, its theoretical motivations, as well as recent empirical results related to the topic. The data-driven trigger that allows the NOvA experiment to collect the signal-like events constitutes a major work of this thesis and will be described in detail. Following the discussion of the trigger, the main focus is placed on the development of a selection method to further classify collected events into the signal candidates and the background. An analysis approach in which the real data is partially unblinded to assist the development and evaluation of the event selection is chosen for this search. Because this is an ongoing work and important aspects of the analysis has not been all finalized, this thesis closes out with a sensitivity study. By analyzing the data from 4 months of Far Detector exposure, a 90% C.L. sensitivity limit of 4 × 10³⁰ years was placed on the oscillation life-time of bound neutrons inside the ¹²C targets. This is equivalent to a sensitivity of 0.57 × 10⁸ s placed on the oscillation life-time of free neutrons.Physic