Depth of maximum of air-shower profiles: testing the compatibility of measurements performed at the Pierre Auger Observatory and the Telescope Array experiment

¹ Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
² University of Adelaide, Adelaide, S.A., Australia
³ High Energy Astrophysics Institute & Department of Physics and Astronomy, University of Utah, Salt Lake City, USA
⁴ Instituto de Física de Säo Carlos, Universidade de Säo Paulo, Säo Carlos, Brasil
⁵ Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba, Japan
⁶ Graduate School of Science, Osaka City University, Osaka, Osaka, Japan
⁷ Karlsruhe Institute of Technology, Institut für Kernphysik, Karlsruhe, Germany
⁸ Observatorio Pierre Auger, Av. San Martín Norte 304, 5613, Malargüe, Argentina
⁹ Telescope Array Project, 201 James Fletcher Bldg, 115 S. 1400 East, Salt Lake City, UT 84112 0830, USA

^* e-mail: auger_spokespersons@fnal.gov Full author list: http://www.auger.org/archive/authors_2018_10.html
^** e-mail: whanlon@cosmic.utah.edu Full author list: http://www.telescopearray.org/research/collaborators

Published online: 17 May 2019

Abstract

At the Pierre Auger Observatory and the Telescope Array, the measurements of depths of maximum of airshower profiles, X_max, are performed using direct observations of the longitudinal development of showers with the help of the fluorescence telescopes. Though the same detection technique is used at both installations, the straightforward comparison of the characteristics of the measured X_max distributions is not possible due to the different approaches to the analysis of the recorded events. In this work, the Auger – Telescope Array composition working group presents a technique to compare the X_max measurements from the Auger Observatory and the Telescope Array. Applying this technique the compatibility of the first two moments of the measured X_max distributions is qualitatively tested for energies 10^18.2 eV < E < 10^19.0 eV using the recently published Telescope Array data from the Black Rock Mesa and Long Ridge fluorescence detector stations. For a quantitative comparison, simulations of air showers with EPOS-LHC, folded with effects of the Telescope Array detector, are required along with the inclusion in the analysis of the systematic uncertainties in the measurements of X_max and the energies of the events.