Title

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

Authors

A. Aab, Universität Siegen
P. Abreu, Instituto Superior Técnico
M. Aglietta, Istituto Nazionale Di Astrofisica, Rome
E. J. Ahn, Fermi National Accelerator Laboratory
I. Al Samarai, Laboratoire de Physique Nucléaire et de Hautes Energies
I. F.M. Albuquerque, Universidade de Sao Paulo - USP
I. Allekotte, Instituto Balseiro
P. Allison, The Ohio State University
A. Almela, Consejo Nacional de Investigaciones Científicas y Técnicas
J. Alvarez Castillo, Universidad Nacional Autónoma de México
J. Alvarez-Muñiz, Universidad de Santiago de Compostela
R. Alves Batista, Universität Hamburg
M. Ambrosio, Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
L. Anchordoqui, Lehman College
B. Andrada, Consejo Nacional de Investigaciones Científicas y Técnicas
S. Andringa, Instituto Superior Técnico
C. Aramo, Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
F. Arqueros, Universidad Complutense de Madrid
N. Arsene, Universitatea din Bucuresti
H. Asorey, Instituto Balseiro
P. Assis, Instituto Superior Técnico
J. Aublin, Laboratoire de Physique Nucléaire et de Hautes Energies
G. Avila, Pierre Auger Observatory
N. Awal, New York University
A. M. Badescu, University Politehnica of Bucharest
C. Baus, Karlsruhe Institute of Technology
J. J. Beatty, The Ohio State University
K. H. Becker, Bergische Universitat Wuppertal
J. A. Bellido, The University of Adelaide
C. Berat, Universite Grenoble Alpes
M. E. Bertaina, Istituto Nazionale di Fisica Nucleare, Sezione di Torino
X. Bertou, Instituto Balseiro

Document Type

Article

Publication Date

4-7-2016

Abstract

© 2016 American Physical Society. 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.

Publication Title

Physical Review D

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