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This content will become publicly available on April 7, 2017

Title: Azimuthal asymmetry in the risetime of the surface detector signals of the Pierre Auger Observatory

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 x 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. Furthermore, the method has uncovered further deficiencies in our understanding of shower modelling that must be resolved before the mass composition can be inferred from (secθ)max.
Authors:
 [1]
  1. Univ. Siegen (Germany). et al.
Publication Date:
OSTI Identifier:
1247529
Report Number(s):
FERMILAB-PUB--16-094-AD-AE-CD-TD; arXiv:1604.00978
Journal ID: ISSN 2470-0010; PRVDAQ; 1441175
Grant/Contract Number:
AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 93; Journal Issue: 7; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Research Org:
Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
Pierre Auger Collaboration
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS