Muon-induced neutral particle background for a shallow depth Iron Calorimeter detector

Abstract

The 51 kton Iron Calorimeter (ICAL) detector for measuring atmospheric muon neutrinos and muon anti-neutrinos separately will enable addressing the neutrino mass hierarchy problem. This will be the flagship experiment at the India based Neutrino Observatory (INO) and will be located in a cavern in a mountain with a rock cover of 1 km in all directions. This will help reduce the cosmic muon background by a factor of 106 with respect to that at sea level. In this work, the possibility of a 100 m shallow depth ICAL (SICAL) is explored. To achieve a similar cosmic muon background reduction as at 1 km depth a cosmic muon veto detector (CMVD) which can reject muons with an efficiency of 99.99% is required. However an important background could be neutral long lived particles such as neutrons and K0 L produced in interactions of muons with rock closest to ICAL. The charged particles produced in muon-nuclear interactions can be vetoed but the neutral particle can pass through CMVD undetected and subsequently mimic a neutrino like event in ICAL In this contribution the results of a GEANT4 based simulation to estimate this background in SICAL are presented.