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Cosmic-ray anisotropies in right ascension measured by the Pierre Auger Observatory

Journal Article · · Astrophys.J.
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  1. Nijmegen U., IMAPP
  2. LIP, Lisbon
  3. Turin Observ.; INFN, Turin
  4. Sao Paulo U.
  5. Adelaide U.
  6. Centro Atomico Bariloche
  7. ITeDA, Buenos Aires; U. Tech. Natl., Argentina
  8. Mexico U.
  9. Santiago de Compostela U.
  10. Turin U.; INFN, Turin
  11. Lehman Coll.
  12. ITeDA, Buenos Aires
  13. INFN, Naples
  14. Aachen, Tech. Hochsch.
  15. Pierre Auger Observ.
  16. Bucharest, Polytechnic Inst.
  17. Prague, Inst. Phys.
  18. Bucharest, IFIN-HH
  19. Naples U.; INFN, Naples
  20. Wuppertal U.
  21. LPSC, Grenoble
  22. Bonn, Max Planck Inst., Radioastron.
  23. Orsay, IPN
  24. L'Aquila U.; Gran Sasso
  25. Rio de Janeiro Federal U.
  26. Cracow, INP
  27. ITeDA, Buenos Aires; KIT, Karlsruhe, IKP
  28. Colorado State U.
  29. Siegen U.
  30. Granada U., Theor. Phys. Astrophys.
  31. Vrije U., Brussels
  32. Catania U.; INFN, Catania
  33. Chiapas Autonoma U.
  34. Milan U.
  35. La Plata U.
  36. U. Tech. Natl., Argentina; ITeDA, Buenos Aires
  37. Nijmegen U., IMAPP; Nikhef, Amsterdam
  38. U. Sao Paulo (main)
  39. INFN, Lecce
  40. Campinas State U.
  41. Brussels U.
  42. Palacky U.
  43. Natl. Tech. U., San Rafael
  44. Delaware U.; Delaware U., Bartol Inst.
  45. Salento U.; INFN, Lecce
  46. INFN, Aquila; Gran Sasso
  47. INFN, Milan; Milan Polytechnic
  48. Case Western Reserve U.
  49. Buenos Aires, IAFE; Buenos Aires U.
  50. KIT, Karlsruhe, IKP
  51. Niteroi, Fluminense U.
  52. Rio de Janeiro Federal U.; Valongo Observ.
  53. Sao Paulo U., Sao Carlos
  54. KIT, Karlsruhe, ETP
  55. INFN, Turin
  56. Parana U.
  57. KIT, Karlsruhe, ETP; KIT, Karlsruhe, IKP
  58. Fermilab
  59. Nijmegen U., IMAPP; ASTRON, Dwingeloo; Nikhef, Amsterdam
  60. Chicago U., EFI
  61. New York U.
  62. KIT, Karlsruhe, IPE
  63. Michigan Tech. U.
  64. Stefan Inst., Ljubljana; Nova Gorica U.
  65. IFIR, Rosario
  66. Milan U.; INFN, Milan
  67. INFN, Milan
  68. U. Lodz (main)
  69. Centro Atomico Bariloche; KIT, Karlsruhe, IKP
  70. UEFS, Feira de Santana
  71. INFN, Turin; Turin U.
  72. KIT, Karlsruhe, IKP; ITeDA, Buenos Aires
  73. KIT, Karlsruhe, IKP; Vrije U., Brussels
  74. Bucharest, Inst. Space Science
  75. Colorado School of Mines
  76. Nova Gorica U.
  77. CEFET, Rio de Janeiro
  78. ABC Federal U.
  79. Paris U., VI-VII
  80. Puebla U., Inst. Fis.
  81. Hamburg U., Inst. Theor. Phys. II
  82. Louisiana State U.
  83. Rome U., Tor Vergata; INFN, Rome2
  84. Penn State U.
  85. Campinas State U.; Rio de Janeiro Federal U.
  86. Charles U.
  87. Cantabria U., Santander
  88. LIDAR CITEFA
  89. UPII, IPN
  90. Nikhef, Amsterdam; Nijmegen U., IMAPP
  91. Buenos Aires, IAFE
  92. INFN, Rome2
  93. Salento U.; INFN, Lecce; Orsay, IPN
  94. KIT, Karlsruhe, ETP; ITeDA, Buenos Aires
  95. Groningen, KVI; Vrije U., Brussels
  96. Delaware U.; Delaware U., Bartol Inst.; KIT, Karlsruhe, IKP
  97. Rio de Janeiro, CBPF
  98. Medellin U.
  99. Valongo Observ.
  100. Vrije U., Amsterdam
  101. Leeds U.
  102. Nova Gorica U.; Stefan Inst., Ljubljana
  103. CINVESTAV, IPN
+ Show Author Affiliations
We present measurements of the large-scale cosmic-ray anisotropies in right ascension, using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 years. We determine the equatorial dipole component, $$\vec{d}_\perp$$, through a Fourier analysis in right ascension that includes weights for each event so as to account for the main detector-induced systematic effects. For the energies at which the trigger efficiency of the array is small, the ``East-West'' method is employed. Besides using the data from the array with detectors separated by 1500 m, we also include data from the smaller but denser sub-array of detectors with 750 m separation, which allows us to extend the analysis down to $$\sim 0.03$$ EeV. The most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8~EeV, $$d_\perp=6.0^{+1.0}_{-0.9}$$%, which is inconsistent with isotropy at the 6$$\sigma$$ level. In the bins below 8 EeV, we obtain 99% CL upper-bounds on $$d_\perp$$ at the level of 1 to 3 percent. At energies below 1 EeV, even though the amplitudes are not significant, the phases determined in most of the bins are not far from the right ascension of the Galactic center, at $$\alpha_{\rm GC}=-94^\circ$$, suggesting a predominantly Galactic origin for anisotropies at these energies. The reconstructed dipole phases in the energy bins above 4 EeV point instead to right ascensions that are almost opposite to the Galactic center one, indicative of an extragalactic cosmic ray origin.
Research Organization:
ABC Federal U.; ASTRON, Dwingeloo; Aachen, Tech. Hochsch.; Adelaide U.; Bonn, Max Planck Inst., Radioastron.; Brussels U.; Bucharest, IFIN-HH; Bucharest, Inst. Space Science; Bucharest, Polytechnic Inst.; Buenos Aires U.; Buenos Aires, IAFE; CEFET, Rio de Janeiro; CINVESTAV, IPN; Campinas State U.; Cantabria U., Santander; Case Western Reserve U.; Catania U.; Centro Atomico Bariloche; Charles U.; Chiapas Autonoma U.; Chicago U., EFI; Colorado School of Mines; Colorado State U.; Cracow, INP; Delaware U.; Delaware U., Bartol Inst.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Gran Sasso; Granada U., Theor. Phys. Astrophys.; Groningen, KVI; Hamburg U., Inst. Theor. Phys. II; IFIR, Rosario; INFN, Aquila; INFN, Catania; INFN, Lecce; INFN, Milan; INFN, Naples; INFN, Rome2; INFN, Turin; ITeDA, Buenos Aires; KIT, Karlsruhe, ETP; KIT, Karlsruhe, IKP; KIT, Karlsruhe, IPE; L'Aquila U.; LIDAR CITEFA; LIP, Lisbon; LPSC, Grenoble; La Plata U.; Leeds U.; Lehman Coll.; Louisiana State U.; Medellin U.; Mexico U.; Michigan Tech. U.; Milan Polytechnic; Milan U.; Naples U.; Natl. Tech. U., San Rafael; New York U.; Nijmegen U., IMAPP; Nikhef, Amsterdam; Niteroi, Fluminense U.; Nova Gorica U.; Orsay, IPN; Palacky U.; Parana U.; Paris U., VI-VII; Penn State U.; Pierre Auger Observ.; Prague, Inst. Phys.; Puebla U., Inst. Fis.; Rio de Janeiro Federal U.; Rio de Janeiro, CBPF; Rome U., Tor Vergata; Salento U.; Santiago de Compostela U.; Sao Paulo U.; Sao Paulo U., Sao Carlos; Siegen U.; Stefan Inst., Ljubljana; Turin Observ.; Turin U.; U. Lodz (main); U. Sao Paulo (main); U. Tech. Natl., Argentina; UEFS, Feira de Santana; UPII, IPN; Valongo Observ.; Vrije U., Amsterdam; Vrije U., Brussels; Wuppertal U.
Sponsoring Organization:
US Department of Energy
Grant/Contract Number:
AC02-07CH11359
OSTI ID:
1602988
Alternate ID(s):
OSTI ID: 23086736
Report Number(s):
FERMILAB-PUB-20-076; FERMILAB-PUB-20-076-ND-PPD-TD; oai:inspirehep.net:1780872; arXiv:2002.06172
Journal Information:
Astrophys.J., Journal Name: Astrophys.J. Vol. 891
Country of Publication:
United States
Language:
English

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