The magnetised Iron CALorimeter detector (ICAL), proposed to be built at the India-based Neutrino Observatory (INO), is designed to study atmospheric neutrino oscillations. The ICAL detector is optimized to measure the muon momentum, its direction and charge. A GEANT4-based package has been developed by the INO collaboration to simulate the ICAL geometry and propagation of particles through the detector. The simulated muon tracks are reconstructed using the Kalman Filter algorithm. Here we present the first study of the response of the ICAL detector to muons using this simulations package to determine the muon momentum and direction resolutions as well as their reconstruction and charge identification efficiencies. For 1-20 GeV/c muons in the central region of the detector, we obtain an average angle-dependent momentum resolution of 9-14%, an angular resolution of about a degree, reconstruction efficiency of about 80% and a correct charge identification of about 98%.

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles. v Physics Potential of ICAL at INO vi PrefaceThe past two decades in neutrino physics have been very eventful, and have established this field as one of the flourishing areas of high energy physics. Starting from the confirmation of neutrino oscillations that resolved the decades-old problems of the solar and atmospheric neutrinos, we have now been able to show that neutrinos have nonzero masses, and different flavors of neutrinos mix among themselves. Our understanding of neutrino properties has increased by leaps and bounds. Many experiments have been constructed and envisaged to explore different facets of neutrinos, in particular their masses and mixing.The Iron Calorimeter (ICAL) experiment at the India-based Neutrino Observatory (INO) [1] is one of the major detectors that is expected to see the light of the day soon. It will have unique features like the ability to distinguish muon neutrinos from antineutrinos at GeV energies, and measure the energies of hadrons in the same energy range. It is therefore well suited for the identification of neutrino mass hierarchy, the measurement of neutrino mixing parameters, and many probes of new physics. The site for the INO has been identified, and the construction is expected to start soon. In the meanwhile, the R&D for the ICAL detector, including the design of its modules, the magnet coils, the active detector elements and the associated electronics, has been underway over the past deca...

The magnetized Iron CALorimeter detector (ICAL) which is proposed to be built in the India-based Neutrino Observatory (INO) laboratory, aims to study atmospheric neutrino oscillations primarily through charged current interactions of muon neutrinos and anti-neutrinos with the detector. The response of muons and charge identification efficiency, angle and energy resolution as a function of muon momentum and direction are studied from GEANT4-based simulations in the peripheral regions of the detector. This completes the characterisation of ICAL with respect to muons over the entire detector and has implications for the sensitivity of ICAL to the oscillation parameters and mass hierarchy compared to the studies where only the resolutions and efficiencies of the central region of ICAL were assumed for the entire detector.Selection criteria for track reconstruction in the peripheral region of the detector were determined from the detector response. On applying these, for the 1-20 GeV energy region of interest for mass hierarchy studies, an average angle-dependent momentum resolution of 15-24%, reconstruction efficiency of about 60-70% and a correct charge identification of about 97% of the reconstructed muons were obtained. In addition, muon response at higher energies upto 50 GeV was studied as relevant for understanding the response to so-called rock muons and cosmic ray muons. An angular resolution of better than a degree for muon energies greater than 4 GeV was obtained in the peripheral regions, which is the same as that in the central region.

Discharge probability in GEM-based gaseous detectors has been numerically estimated using an axisymmetric hydrodynamic model. Initial primary charge configurations in the drift region, obtained using Heed and Geant4, are found to have significant effect on the subsequent evolution of detector response. Simulation of energy resolution has been performed to establish the capability of the hydrodynamic model to capture statistical nature of the experimental situation. Finally, single and triple GEM configurations exposed to alpha sources have been simulated to estimate discharge probability which have been compared with available experimental data. Despite the simplifying and drastic assumptions in the numerical model, the comparisons are encouraging.

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