## Resumen

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, X_{max}, 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 X_{max}, 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 10^{18.7} 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 X_{max} from the on-plane region is found to have a 9.1 ± 1.6^{+} _{−} ^{2} _{2} ^{1} _{2} g/cm^{2} shallower mean and a 5.9 ± 2.1^{+} _{−} ^{3} _{2} ^{5} _{5} g/cm^{2} 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^{+} _{−} ^{1} _{1} ^{4} _{5} 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 10^{18.7} 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.

Idioma original | Inglés estadounidense |
---|---|

- | 321 |

Publicación | Proceedings of Science |

Volumen | 395 |

Estado | Indizado - 18 mar. 2022 |

Publicado de forma externa | Sí |

Evento | 37th International Cosmic Ray Conference, ICRC 2021 - Virtual, Berlin, Alemania Duración: 12 jul. 2021 → 23 jul. 2021 |

### Nota bibliográfica

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## Huella

Profundice en los temas de investigación de 'Indication of a mass-dependent anisotropy above 10^{18.7}eV in the hybrid data of the Pierre Auger Observatory'. En conjunto forman una huella única.