Measuring dark neutrinos and light using external and internal components of LArTPCs

The so-called MiniBooNE low-energy excess has been a long-standing question for beyond Standard Model (BSM) physics in the neutrino field. The Short Baseline Neutrino (SBN) program was proposed to investigate and provide further insights into this excess. The SBN program utilises Liquid Argon Time Projection Chamber (LArTPC) technology, which allows for precise measurements of neutrino interactions and holds great potential for addressing significant open questions in the field. Within the SBN program, the Short Baseline Near Detector (SBND) plays a crucial role as one of the near detector, positioned just 110 meters from the neutrino source. Being located on the surface, SBND is exposed to cosmic-ray background, and to mitigate this, the Cosmic Ray Tagger (CRT) system has been implemented to identify and veto cosmic background events, thereby enhancing the purity of neutrino interactions. Additionally, the CRT system can be used to search for BSM signatures, such as the dark neutrinos, which have been proposed to explain the MiniBooNE low-energy excess. This thesis presents a novel approach for searching for dark neutrinos using existing SBND CRT data, collected with a unique setup called the CRT Beam Telescope. An extended model-independent search based on the dark neutrino analysis is also presented. The sensitivity plot for the CRT Beam Telescope is compared with an estimated MiniBooNE exclusion limit. Furthermore, this thesis covers the commissioning work conducted for the SBND CRT system, which is vital for ensuring optimal performance. The LArTPC technology also benefits from liquid argon’s excellent scintillation properties, producing abundant scintillation light. This thesis describes a method developed to understand the detector response to the scintillation light produced across the LArTPC, enhancing our understanding of the detector’s performance and facilitating more accurate measurements.