Joint analysis of the energy spectrum of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory and the Telescope Array

TELESCOPE ARRAY AND PIERRE AUGER COLLABORATION; A. MARIAZZI

Berlin

Conferencia; 37th International Cosmic Ray Conference (ICRC2021); 2021

The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is of crucialimportance to clarify their origin and acceleration mechanisms. The Pierre Auger Observatory inArgentina and the Telescope Array (TA) in the US have reported their measurements of UHECRenergy spectra observed in the southern and northern hemisphere, respectively. The region of thesky accessible to both Observatories ([−15, +24] degrees in declination) can be used to crosscalibrate the two spectra. The Auger-TA energy spectrum working group was organized in 2012and has been working to understand the uncertainties in energy scale in both experiments, theirsystematic differences, and differences in the shape of the spectra. In previous works, we reportedthat there was an overall agreement of the energy spectra measured by the two observatories below10 EeV while at higher energies, a remaining significant difference was observed in the commondeclination band. We revisit this issue to understand its origin by examining the systematicuncertainties, statistical effects, and other possibilities. We will also discuss the differences in thespectra in different declination bands and a new feature in the spectrum recently reported by theAuger Collaboration.