Monte Carlo studies for improving the sensitivity of the TACTIC telescope by using zenith angle dependent Dynamic Supercuts

The sensitivity of atmospheric Cerenkov imaging telescopes is strongly dependent on the rejection of the cosmic ray background events. While the efcienc y of using Hillas parameters for performing this segregation has been conrmed by the detection of several -ray sources by various independent groups, one has to also consider energy and zenith angle dependence of these parameters so that the energy spectrum of the -ray source can be reliably determined. The main aim of the present simulation work is to study the comparative performance of various -ray selection methodologies at different zenith angles so that zenith angle dependent Dynamic Supercuts procedure can be used for the TACTIC telescope for determining the energy spectrum of a source. The results of the Monte Carlo simulations, carried out at four different zenith angle values of 15 , 25 , 35 and 45 , indicate that the zenith angle dependent Dynamic Supercuts provide the best combination of sensitivity and -ray acceptance as compared to the Supercuts and the Dynamic Supercuts methodologies.