Large-scale and multipolar anisotropies of cosmic rays detected at the Pierre Auger Observatory with energies above 4 EeV
Rogério de Almeida, P. Abreu, M. Aglietta, Justin M. Albury, I. Allekotte, Alejandro Almela, Jaime Álvarez-Muñiz, Rafael Alves Batista, Gioacchino Alex Anastasi, Luis A. Anchordoqui, Belén Andrada, S. Andringa, C. Aramo, Paulo Ricardo Araújo Ferreira, Juan Carlos Arteaga Velázquez, Hernán Gonzalo Asorey, P. Assis, Gualberto Avila, Alina Mihaela Badescu, Alena Bakalová, Alexandru Balaceanu, Felicia Barbato, Ricardo Jorge Barreira Luz, Karl‐Heinz Becker, Jose A. Bellido, Corinne Bérat, М. Бертаина, X. Bertou, Peter L. Biermann, Virginia Binet, Kathrin Bismark, Teresa Bister, Jonathan Biteau, Jiří Blažek, C. Bleve, Martina Boháčová, Denise Boncioli, C. Bonifazi, Luan Bonneau Arbeletche, Nataliia Borodai, Ana Martina Botti, Jeffrey Brack, T. Bretz, P. Gabriel Brichetto Orchera, Florian Lukas Briechle, P. Buchholz, A. Bueno, S. Buitink, Mario Buscemi, Max Büsken, K. S. Caballero‐Mora, Lorenzo Caccianiga, Fabrizia Canfora, Ioana Caracas, Juan Miguel Carceller, R. Caruso, A. Castellina, Fernando Catalani, G. Cataldi, Lorenzo Cazon, Marcos Cerda, J. A. Chinellato, J. Chudoba, L. Chytka, R. W. Clay, Agustín Cobos Cerutti, Roberta Colalillo, Alan Coleman, Maria Rita Coluccia, R. Conceição, Antonio Condorelli, Giovanni Consolati, F. Contreras, Fabio Convenga, Diego Correia dos Santos, C. E. Covault, S. Dasso, K. Daumiller, B. R. Dawson, Jarryd A. Day, Rogerio M. de Almeida, Joaquin de Jesus, S. J. de Jong, G. De Mauro, João de Mello Neto, I. De Mitri, Jaime de Oliveira, Danelise de Oliveira Franco, Francesco de Palma, Vitor de Souza, Emanuele De Vito, Mariano del Río, Olivier Deligny, Luca Deval, Armando di Matteo, C. Dobrigkeit, Juan Carlos D’Olivo, Luis Miguel Domingues Mendes, Rita Cassia dos Anjos, Diego dos Santos
Abstract
More than half a century after the discovery of ultra-high energy cosmic rays (UHECRs), their origin is still an open question. The study of anisotropies in the arrival directions of such particles is an essential ingredient to solve this puzzle. We update our previous analysis of large-scale anisotropies observed by the Pierre Auger Observatory using the latest data collected before the AugerPrime upgrade. We select events with zenith angles up to 80 degrees, implying a sky coverage of 85$\%$, and energies above 4 EeV, for which the surface detector of the Observatory is fully efficient. Dipolar and quadrupolar amplitudes are evaluated through a combined Fourier analysis of the event count rate in right ascension and azimuth. The analysis is performed in three energy bins with boundaries at 4, 8, 16 and 32 EeV and two additional cumulative bins with energies above 8 and 32 EeV. The most significant signal is a dipolar modulation in right ascension for energies above 8 EeV, as previously reported, with statistical significance of $6.6\sigma$. Additionally, we report the measurements of the angular power spectrum for the same energy bins with the same dataset.