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

THE PIERRE AUGER COLLABORATION (A. AAB, ..., A.D. SUPANITSKY, ...)

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2015 vol. 91 p. 1 - 14

1550-7998

Neutrinos in the cosmic ray flux with energies near 1 EeV and above are detectable with the SurfaceDetector array (SD) of the Pierre Auger Observatory. We report here on searches through Auger data from1 January 2004 until 20 June 2013. No neutrino candidates were found, yielding a limit to the diffuse flux of ultrahigh energy neutrinos that challenges the Waxman-Bahcall bound predictions. Neutrino identification is attempted using the broad time structure of the signals expected in the SD stations, and is efficiently done for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well asfor "Earth-skimming" neutrino interactions in the case of tau neutrinos. In this paper the searches for downward-going neutrinos in the zenith angle bins 60deg-75deg and 75deg-90deg 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 neutrinos with an E −2 spectrum in the energy range 1.0 x 10^17 eV - 2.5 x 10^19 eV isE^2 dN/dE < 6.4 x 10^−9 GeV cm^−2 s^−1 sr^−1 .