About the consistency of the energy scales of past and present instruments detecting cosmic rays above the ankle energy

TL;DR

This paper compares cosmic ray energy spectra from various experiments above 10^19 eV, highlighting inconsistencies in energy scales and the notably low number of ultra-high-energy events detected by Auger compared to others.

Contribution

It provides a detailed analysis of the energy scale discrepancies among eleven cosmic ray detectors and discusses their impact on observed flux differences.

Findings

Spectra from Telescope Array, HiRes, and Yakutsk align better with predictions.

Auger data shows significantly fewer events above 10^20 eV than other experiments.

Energy scale inconsistencies may explain flux measurement discrepancies.

Abstract

The energy spectrum of the cosmic radiation in the range 10$^{19}$-2.4$\times$10$^{21}$ eV has been recently predicted showing a rich and distinctive staircase profile. In order to check the prediction, the spectra measured by running and past experiments above 10$^{19}$ eV are examined. The computed spectrum compares more favourably with the Telescope Array, HiRes I and Yakutsk data rather than with the Auger data in the range (1-20)$\times$10$^{19}$ eV. Previous flux measurements by Haverah Park, {\sc sugar}, {\sc agasa} and Fly's Eye experiments are above the predicted spectrum in the limited band (1-30)$\times$10$^{19}$ eV. The flux measured by the Auger Group in the band (8-18)$\times$10$^{19}$ eV is below those of all other experiments and below the prediction. The energy scales of the instruments might be at the origin of the flux mismatch among the experiments. Accordingly, the energy scales of all the eleven instruments operating above 10$^{20}$ eV are examined and the major inconsistencies discerned. The paucity of events above 10$^{20}$ eV of the Auger experiment with respect to all others is by far the major puzzle emerging from this scrutiny. The Auger instrument recorded only 4 events above 10$^{20}$ eV with an exposure exceeding 42500 km$^{2}$ sr year while the Telescope Array recorded 13 events with an exposure of 8100 km$^{2}$ sr year. A tentative solution of this puzzle is ventilated.