A. Aab (Author), Andrej Filipčič (Author), Gašper Kukec Mezek (Author), A. Saleh (Author), Samo Stanič (Author), M. Trini (Author), Darko Veberič (Author), Serguei Vorobiov (Author), Lili Yang (Author), Danilo Zavrtanik (Author), Marko Zavrtanik (Author)

Abstract

The azimuthal asymmetry in the risetime of signals in Auger surface detector stations is a source of information on shower development. The azimuthal asymmetry is due to a combination of the longitudinal evolution of the shower and geometrical effects related to the angles of incidence of the particles into the detectors. The magnitude of the effect depends upon the zenith angle and state of development of the shower and thus provides a novel observable, (secθ)max, sensitive to the mass composition of cosmic rays above 3×1018  eV. By comparing measurements with predictions from shower simulations, we find for both of our adopted models of hadronic physics (QGSJETII-04 and EPOS-LHC) an indication that the mean cosmic-ray mass increases slowly with energy, as has been inferred from other studies. However, the mass estimates are dependent on the shower model and on the range of distance from the shower core selected. Thus the method has uncovered further deficiencies in our understanding of shower modeling that must be resolved before the mass composition can be inferred from (secθ)max.

Keywords

ultra-high energy cosmic rays;UHECR mass composition;Pierre Auger Observatory;extensive air showers;Auger Surface Detector signals risetime;azimuthal symmetry;

Data

Language: English
Year of publishing:
Typology: 1.01 - Original Scientific Article
Organization: UNG - University of Nova Gorica
UDC: 539.1
COBISS: 4244731 Link will open in a new window
ISSN: Y508-3435
Views: 4663
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Other data

URN: URN:SI:UNG
Type (COBISS): Not categorized
Pages: str. 072006-1-072006-16
Volume: ǂVol. ǂ93
Issue: ǂno. ǂ7
Chronology: 2016
DOI: 10.1103/PhysRevD.93.072006
ID: 9136393