ANN based energy estimation procedure and energy spectrum of the Crab Nebula as measured by the TACTIC gamma-ray telescope

A novel energy reconstruction procedure based on the utilization of Artificial Neural Network has been developed for the TACTIC atmospheric Cerenkov imaging telescope to estimate the energy of the primary gammarays in the TeV energy range. The procedure uses a 3:20:1 configuration of the ANN with resilient backpropagation training algorithm to estimate the energy of a γ-ray like event on the basis of its image SIZE, DISTANCE and zenith angle. The results obtained by using the CORSIKA code simulated data suggest the energy resolution of the telescope is ∼ 40 for retaining ∼90 of the γ-ray events in a particular energy bin which is comparable to the energy resolution of other single element imaging telescopes. Details of the energy estimation procedure along with results obtained by determining the Crab Nebula energy spectrum in the energy range 1-16 TeV as measured by the TACTIC telescope are presented in the paper.