Published December 23, 2025
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Measuring the muon content of inclined air showers using AERA and the water-Cherenkov detectors of the Pierre Auger Observatory

Creators

  • 1. University of Adelaide
  • 2. Universidade de Lisboa—UL
  • 3. Osservatorio Astrofisico di Torino (INAF)
  • 4. INFN
  • 5. Istituto Nazionale di Fisica Nucleare
  • 6. Centro Atómico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET)
  • 7. Nationaal Instituut voor Kernfysica en Hoge Energie Fysica (NIKHEF)
  • 8. Radboud University Nijmegen
  • 9. Instituto de Tecnologías en Detección y Astropartículas (CNEA, CONICET, UNSAM)
  • 10. Universidad Tecnológica Nacional—Facultad Regional Buenos Aires
  • 11. Gran Sasso Science Institute
  • 12. INFN Laboratori Nazionali del Gran Sasso
  • 13. Universidade de Santiago de Compostela
  • 14. University of Santiago de Compostela
  • 15. Università di Catania
  • 16. City University of New York
  • 17. Università di Milano
  • 18. Università Torino
  • 19. Universidad Michoacana de San Nicolás de Hidalgo
  • 20. Observatorio Pierre Auger and Comisión Nacional de Energía Atómica
  • 21. Università dell'Aquila
  • 22. Institute of Physics of the Czech Academy of Sciences
  • 23. Academy of Sciences of the Czech Republic
  • 24. Colorado School of Mines
  • 25. University Grenoble Alpes
  • 26. Instituto de Física de Rosario (IFIR)
  • 27. Karlsruhe Institute of Technology (KIT)
  • 28. Karlsruhe Institute of Technology
  • 29. Université Paris-Saclay
  • 30. International Center of Advanced Studies and Instituto de Ciencias Físicas
  • 31. Universidade Estadual de Campinas (UNICAMP)
  • 32. State University of Campinas
  • 33. Institute of Nuclear Physics PAN
  • 34. RWTH Aachen University
  • 35. Universidad de Granada and C.A.F.P.E.
  • 36. University of Granada
  • 37. Vrije Universiteit Brussels
  • 38. Universidad Autónoma de Chiapas
  • 39. Universidad Tecnológica Nacional
  • 40. Universidade de São Paulo
  • 41. University of São Paulo
  • 42. Observatorio Pierre Auger
  • 43. Palacky University
  • 44. Università di Napoli "Federico II,"
  • 45. Politecnico di Milano
  • 46. Polytechnic University of Milan
  • 47. Università del Salento
  • 48. Universidade Federal do Rio de Janeiro
  • 49. Federal University of Rio de Janeiro
  • 50. Case Western Reserve University
  • 51. Universität Siegen
  • 52. Universidad Nacional de La Plata and CONICET
  • 53. Instituto de Astronomía y Física del Espacio (IAFE, CONICET-UBA)
  • 54. Universidad de Buenos Aires and CONICET
  • 55. University of Buenos Aires
  • 56. Instituto Federal de Educação
  • 57. Universität Hamburg
  • 58. University of Hamburg
  • 59. Universidad Nacional Autónoma de México
  • 60. National Autonomous University of Mexico
  • 61. Centro Brasileiro de Pesquisas Fisicas
  • 62. Universidade Federal do Paraná
  • 63. Federal University of Paraná
  • 64. Stichting Astronomisch Onderzoek in Nederland (ASTRON)
  • 65. New York University
  • 66. Université Libre de Bruxelles (ULB)
  • 67. Université libre de Bruxelles
  • 68. Michigan Technological University
  • 69. J. Stefan Institute
  • 70. University of Nova Gorica
  • 71. University of Delaware
  • 72. University of Chicago
  • 73. Bergische Universität Wuppertal
  • 74. Universidade Estadual de Feira de Santana
  • 75. Institute of Space Science
  • 76. Centro Federal de Educação Tecnológica Celso Suckow da Fonseca
  • 77. Universidade Federal do ABC
  • 78. Université de Paris
  • 79. University of Paris
  • 80. Università di Palermo
  • 81. Università di Roma "Tor Vergata"
  • 82. Laboratorio Atmósfera—Departamento de Investigaciones en Láseres y sus Aplicaciones—UNIDEF (CITEDEF-CONICET)
  • 83. Charles University
  • 84. Charles University in Prague
  • 85. Universidad Industrial de Santander
  • 86. Unidad Profesional Interdisciplinaria en Ingeniería y Tecnologías Avanzadas del Instituto Politécnico Nacional (UPIITA-IPN)
  • 87. Instituto Politécnico Nacional
  • 88. Universidade Federal de Campina Grande
  • 89. University of Łódź
  • 90. "Horia Hulubei" National Institute for Physics and Nuclear Engineering
  • 91. Benemérita Universidad Autónoma de Puebla
  • 92. Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo (INAF)
  • 93. Universidad de Medellín
  • 94. Universiteit van Amsterdam
  • 95. University of Amsterdam

Description

We present a novel approach for assessing the muon content of air showers with large zenith angles on a combined analysis of their radio emission and particle footprint. We use the radiation energy reconstructed by the Auger engineering radio array (AERA) as an energy estimator and determine the muon number independently with the water-Cherenkov detector array of the Pierre Auger Observatory, deployed on a 1500 m grid. We focus our analysis on air showers with primary energy above 4 EeV to ensure full detection efficiency. Over approximately ten years of accumulated data, we identify a set of 40 high-quality events that are used in the analysis. The estimated muon contents in data are compatible with those for iron primaries as predicted by current-generation hadronic interaction models. This result can be interpreted as a deficit of muons in simulations as a lighter mass composition has been established from X max measurements. This muon deficit was already observed in previous analyses of the Auger Collaboration and is confirmed using hybrid events that include radio measurements for the first time.
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