An improved limit to the diffuse flux of ultra-high energy neutrinos from the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION; N. GONZÁLEZ

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2015 vol. 91

1550-7998

Neutrinos in the cosmic ray flux with energies near 1 EeV and above aredetectable with the Surface Detector array of the Pierre Auger Observatory. Wereport here on searches through Auger data from 1 January 2004 until 20 June2013. No neutrino candidates were found, yielding a limit to the diffuse fluxof ultra-high energy neutrinos that challenges the Waxman-Bahcall boundpredictions. Neutrino identification is attempted using the broadtime-structure of the signals expected in the SD stations, and is efficientlydone for neutrinos of all flavors interacting in the atmosphere at large zenithangles, as well as for "Earth-skimming" neutrino interactions in the case oftau neutrinos. In this paper the searches for downward-going neutrinos in thezenith angle bins 60∘−75∘ and 75∘−90∘ as well as forupward-going neutrinos, are combined to give a single limit. The 90% C.L.single-flavor limit to the diffuse flux of ultra-high energy neutrinos with anE−2 spectrum in the energy range 1.0×1017 eV - 2.5×1019 eV is E2νdNν/dEν<6.4×10−9 GeV cm−2 s−1 sr−1.