Comments concerning the paper "On the calibration of ultra-high energy EASs at the Yakutsk array and Telescope Array" by A.V.Glushkov et. al

TL;DR

This paper refutes a previous claim that the Telescope Array's energy scale is incorrect, demonstrating that the TA's energy deposit formula is accurate and that the earlier conclusion was based on misinterpretation.

Contribution

It clarifies the correct application of the TA energy deposit formula and corrects the Yakutsk Group's misinterpretation, reaffirming the accuracy of TA's energy scale calibration.

Findings

TA's energy deposit formula is validated by Monte Carlo simulations.

The previously claimed incorrect energy scale by Yakutsk Group is disproved.

Excellent agreement between TA simulations and observed data confirms the calibration accuracy.

Abstract

In a recent review of a paper by the Yakutsk Group, submitted to the Journal Physics of Atomic Nuclei and arXiv, the energy scales of the Yakutsk and Telescope Array (TA) experiments were examined. The authors developed a custom detector response simulator incorporating ionization, bremsstrahlung, pair production, and Compton scattering. Applying this simulator to both Yakutsk and TA surface detectors, they concluded that the TA energy scale might be incorrect due to a misdefined ``response unit.'' They referenced the TA's ``energy deposit formula'' from the literature, scaling it by two factors attributed to the thickness and density of the TA scintillator. Their simulations, using the QGSJET-II-04 hadronic interaction model, agreed with TA's calculations for vertical showers but not for inclined showers, suggesting an incorrect VEM unit of 2.05 MeV. However, this conclusion was found to be incorrect. The TA's energy deposit formula, derived from detailed Monte Carlo simulations using GEANT4, accurately represents the most probable energy deposit by a charged particle in the TA scintillator. The value of 2.05 MeV accounts for the scintillator's thickness and density and is validated by excellent agreement between TA's simulated and observed data. The Yakutsk Group's misinterpretation and incorrect application of the TA formula led to their erroneous conclusion.