@article{b0c7e0d88ddb46b389da3f44ffad5d23,
title = "Indication of a mass-dependent anisotropy above 1018.7 eV in the hybrid data of the Pierre Auger Observatory",
abstract = "We test the hypothesis of an anisotropy laying along the galactic plane which depends on the mass of primary cosmic-rays. The sensitivity to primary mass is provided by the depth of shower maximum, Xmax, from hybrid events measured at the Pierre Auger Observatory. The 14 years of available data are split into on- and off-plane regions using the galactic latitude of each event to form two distributions in Xmax, which are compared using the Anderson-Darling 2-samples test. A scan over a subset of the data is used to select an optimal threshold energy of 1018.7 eV and a galactic latitude splitting at |b| = 30◦, which are then set as a prescription for the remaining data. With these thresholds, the distribution of Xmax from the on-plane region is found to have a 9.1 ± 1.6+−2212 g/cm2 shallower mean and a 5.9 ± 2.1+−3255 g/cm2 narrower width than that of the off-plane region. These differences are as such to indicate that the mean mass of primary particles arriving from the on-plane region is greater than that of those coming from the off-plane region. Monte-Carlo studies yield a 4.4 σ post-penalization statistical significance for the independent data. Including the scanned data results in a 4.9+−1145 σ post-penalization statistical significance, where the uncertainties are of systematic origin. Accounting for systematic uncertainties leads to an indication for anisotropy in mass composition above 1018.7 eV at a confidence level of 3.3 σ. The anisotropy is observed independently at each of the four fluorescence telescope sites. Interpretations of possible causes of the observed effect are discussed.",
author = "{The Pierre Auger Collaboration} and E. Mayotte and P. Abreu and M. Aglietta and Albury, {J. M.} and I. Allekotte and A. Almela and J. Alvarez-Mu{\~n}iz and {Alves Batista}, R. and Anastasi, {G. A.} and L. Anchordoqui and B. Andrada and S. Andringa and C. Aramo and {Ara{\'u}jo Ferreira}, {P. R.} and {Arteaga Vel{\'a}zquez}, {J. C.} and H. Asorey and P. Assis and G. Avila and Badescu, {A. M.} and A. Bakalova and A. Balaceanu and F. Barbato and {Bar-Reira Luz}, {R. J.} and Becker, {K. H.} and Bellido, {J. A.} and C. Berat and Bertaina, {M. E.} and X. Bertou and Biermann, {P. L.} and V. Binet and K. Bismark and T. Bister and J. Biteau and J. Blazek and C. Bleve and M. Boh{\'a}{\v c}ov{\'a} and D. Boncioli and C. Bonifazi and {Bonneau Arbeletche}, L. and N. Borodai and Botti, {A. M.} and J. Brack and T. Bretz and {Brichetto Orchera}, {P. G.} and Briechle, {F. L.} and P. Buchholz and A. Bueno and S. Buitink and M. Buscemi and M. B{\"u}sken and Caballero-Mora, {K. S.} and L. 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note = "Publisher Copyright: {\textcopyright} Copyright owned by the author(s).; null ; Conference date: 12-07-2021 Through 23-07-2021",
year = "2022",
month = mar,
day = "18",
language = "Ingl{\'e}s",
volume = "395",
journal = "Proceedings of Science",
issn = "1824-8039",
}