Limit on the diffuse flux of ultrahigh energy tau neutrinos with the surface detector of the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION; DIEGO MELO

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2009 vol. 79 p. 1 - 15

1550-7998

Data collected at the Pierre Auger Observatory are used to establish an upper limit on the diffuse flux of tau neutrinos in the cosmic radiation. Earth-skimming may interact in the Earth?s crust and produce a lepton by means of charged-current interactions. The lepton may emerge from the Earth and decay in the atmosphere to produce a nearly horizontal shower with a typical signature, a persistent electromagnetic component even at very large atmospheric depths. The search procedure to select events induced by decays against the background of normal showers induced by cosmic rays is described. The method usedto compute the exposure for a detector continuously growing with time is detailed. Systematic un-certainties in the exposure from the detector, the analysis, and the involved physics are discussed. No neutrino candidates have been found. For neutrinos in the energy range 2 x 10E17 eV < E < 2 x 10E19 eV, assuming a diffuse spectrum of the form E2, data collected between 1 January 2004 and 30 April 2008 yield a 90% confidence-level upper limit of E2 dN=dE < 9 x 10E8 GeV/cm2/s/sr.