Expected Performance of cosmic muon veto detector at IICHEP, Madurai, India

The purpose of the cosmic muon veto (CMV) detector is to investigate the feasibility of constructing a large-scale neutrino experiment at shallow depths. An extruded plastic scintillator (EPS)-based active veto system for cosmic ray muons is being built around the existing miniICAL detector, which is a scaled-down version of the proposed ICAL detector, at the transit campus of India-based Neutrino Observatory in Madurai, India. The individual detector consists of the extruded plastic scintillator strips (EPS) ($\sim 500\,cm \times 5\,cm\times 1\,cm$) consisting of two WLS fibers to collect scintillation photons and four silicon-photomultipliers (SiPMs) as photo-transducers. Eight such detectors are grouped to form a module, called a tile, which is placed adjacent to one another to cover the entire mini-ICAL detector. To achieve high efficiency and cover the dead space, up to four of these layers are stacked, to form a veto-wall. The CMV detector comprises four walls, one on top, three on the sides, making it an active veto system that covers the miniICAL detector. The performance of scintillators, WLS fibers, SiPM readout systems, and muon reconstruction in the miniICAL have been well established. Using these developments, this work examines the feasibility of building such a large veto system around the miniICAL detector using the GEANT4 toolkit. The efficiency of the CMV is estimated using reconstructed muon tracks in the RPC stack with sufficient hits and good fit quality. The performance of the CMV detector is tested with and without a magnetic field using the muon reconstruction algorithm and extrapolating the same to the veto detector. The goal is to achieve a veto efficiency $>$ $99.99\,\%$ and a false-positive rate of less than $10^{-5}$. By achieving this high level of veto efficiency, the neutrino experiment can be conducted at a much shallower depth ($100\,m$) than what would normally be required ($1.3\,km$).