Improved limit to the diffuse flux of ultrahigh energy neutrinos from the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION, INCLUYE S. MOLLERACH

PHYSICAL REVIEW D - PARTICLE AND FILDS

American Physical Society

Año: 2015 vol. 91

0556-2821

Neutrinos in the cosmic ray flux with energies near 1 EeV and above aredetectable with the Surface Detector array (SD) of the Pierre AugerObservatory. We report here on searches through Auger data from 1January 2004 until 20 June 2013. No neutrino candidates were found,yielding a limit to the diffuse flux of ultrahigh energy neutrinos thatchallenges the Waxman-Bahcall bound predictions. Neutrino identificationis attempted using the broad time structure of the signals expected inthe SD stations, and is efficiently done for neutrinos of all flavorsinteracting in the atmosphere at large zenith angles, as well as for"Earth-skimming" neutrino interactions in the case of tau neutrinos. Inthis paper the searches for downward-going neutrinos in the zenith anglebins 60°-75° and 75°-90° as well as for upward-goingneutrinos, are combined to give a single limit. The 90% C.L.single-flavor limit to the diffuse flux of ultrahigh energy neutrinoswith an E-2 spectrum in the energy range 1.0 ×1017 eV - 2.5 ×1 019 eV isEν2d Nν/d Eν<6.4×10-9 GeV cm-2 s-1sr-1 .