Validation of a new background discrimination method for the TACTIC TeV $\gamma$-ray telescope with Markarian 421 data

Abstract

This paper describes the validation of a new background discrimination method based on Random Forest technique by re-analysing the Markarian 421 (Mrk 421) observations performed by the TACTIC (TeV Atmospheric Cherenkov Telescope with Imaging Camera) gamma-ray telescope. The Random Forest technique is a flexible multivariate method which combines Bagging and Random Split Selection to construct a large collection of decision trees and then combines them to construct a common classifier. Markarian 421 in a high state was observed by TACTIC during December 07, 2005 - April 30, 2006 for 202 h. Previous analysis of this data led to a detection of flaring activity from the source at Energy $>$ 1 TeV. Within this data set, a spell of 97 h revealed strong detection of a gamma-ray signal with daily flux of > 1 Crab unit on several days. Here we re-analyze this spell as well as the data from the entire observation period with the Random Forest method. Application of this method led to an improvement in the signal detection strength by $\sim 26\%$ along with a $\sim 18\%$ increase in detected $\gamma$ rays compared to the conventional Dynamic Supercuts method. The resultant differential spectrum obtained is represented by a power law with an exponential cut off $\Gamma =-2.51\pm 0.10$ and $E_0=4.71\pm 2.20$ TeV. Such a spectrum is consistent with previously reported results and justifies the use of Random Forest method for analyzing data from atmospheric Cherenkov telescopes.

Accepted NIMA

References in corpus (7)

• Implementation of the Random Forest Method for the Imaging Atmospheric Cherenkov Telescope MAGIC
• Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability
• Gamma-Hadron Separation in Very-High-Energy gamma-ray astronomy using a multivariate analysis method
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• The TACTIC atmospheric Cherenkov Imaging telescope
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• Simulation studies for optimizing the trigger generation criteria for the TACTIC telescope

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