Measurement of neutrino interactions with a production of three charged pions in the final state in the MicroBooNE

Mahmud, Tusharadri and Nowak, Jaroslaw (2025) Measurement of neutrino interactions with a production of three charged pions in the final state in the MicroBooNE. Masters thesis, Lancaster University.

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Abstract

This dissertation presents a study of muon neutrino (νµ) interactions in the MicroBooNE experiment that produce a muon and three charged pions (3π +), along with other non-muon, non-pion particles. Using MicroBooNE’s liquid argon time projection chamber (LArTPC) at Fermilab, a comprehensive selection strategy is developed to isolate this complex final state. Both inclusive and specialised selections are implemented, with a focus on incorporating a boosted decision tree (BDT) to enhance background rejection while maintaining signal integrity. Comparative selection cuts analyses for both NuMI and BNB beam configurations show that BDT-based selections significantly improve purity in the final selection cut tables. Though signal efficiency decreases, particularly after the three charged pion cut, the selected events are cleaner and better suited for precision studies. An investigation into the efficiency drop associated with the three pion cut reveals that pion reconstruction especially momentum, track score and proximity to the interaction vertex plays a critical role. This work improves multi-pion event selection in LArTPCs and provides a solid foundation for future analyses of complex neutrino interactions in MicroBooNE and other similar experiments.