Top-Down analysis at 10^17.5 eV

F. SANCHEZ (VER ADJUNTO)

Malargüe

Otro; PUBLICACION INTERNA COLABORACION AUGER (GAP NOTE); 2021

Observatorio Pierre Auger

In this note we present an analysis using high-quality hybrid events measuredwith the SD-750 and HeCo with a reconstructed energy of 10^17.5 eV. The work iscomplementary of previous studies at 10^19.0 eV for which a clear evidence of discrepancy between data and simulations was found and the source of the difference wasattributable to the muonic component of the signal. In this analysis, we also found adiscrepancy of up to 30%, depending on the considered primary and model, betweenthe simulated SD signal and the observed one. Nevertheless, when we tried to identifythe origin of this mismatch, the picture is not so clear as it is at the highest energies.While both considered hadronic interaction models indicate that an energy rescaling(R E ) of about 10% is needed, the muonic components of the signal (R μ ) show opposite trends: QGSJet-II-04 favors a further increase of 13% in the simulated muonicsignal while EPOS-LHC suggests that a decrease of about 22% is needed. To comparethis study with previous analysis from Auger and other experiments, we translatedthe obtained scalings factors to the z parameter. We found that, at 10^17.5 eV, thetop-down results are compatible with predictions from X max measurements.