Upper limit on the diffuse flux of UHE tau neutrinos from the Pierre Auger Observatory

TL;DR

This paper sets an upper limit on the diffuse flux of ultra-high-energy tau neutrinos using data from the Pierre Auger Observatory, constraining models of cosmic neutrino sources at EeV energies.

Contribution

It provides the first stringent upper limit on the diffuse flux of UHE tau neutrinos in the specified energy range based on observational data.

Findings

Upper limit on tau neutrino flux: $E_ u^{2} dN/dE_ u < 1.3 imes 10^{-7}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$

Energy range of analysis: $2 imes 10^{17}$ eV to $2 imes 10^{19}$ eV

Data collected between 2004 and 2007 used for the analysis.

Abstract

The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau-neutrinos $\nu_\tau$ that interact in the Earth's crust. Tau leptons from $\nu_\tau$ charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 is used to place an upper limit on the diffuse flux of $\nu_\tau$ at EeV energies. Assuming an $E_\nu^{-2}$ differential energy spectrum the limit set at 90 % C.L. is $E_\nu^{2} \mathrm{d}N_{\nu_\tau}/\mathrm{d}E_{\nu} < 1.3 \times 10^{-7}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ in the energy range $2\times10^{17} \mathrm{eV} < E_\nu < 2\times10^{19}$ eV.