2005/12/08 by Sergio Palomares-Ruiz, Andrei Irimia, T. Weiler +1 · 1 citation
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Dark Matter and Cosmic Phenomena #Neutrino Physics Research #astro-ph #hep-ph
paper · pdf · doi:10.1103/physrevd.73.083003
published as Phys.Rev.D73:083003,2006 · 40pp, 10 figs
arxiv created 2005/12/08 · openalex publication_date 2006/04/14 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Detection of ultrahigh energy neutrinos will be useful for unraveling the dynamics of the most violent sources in the cosmos and for revealing the neutrino cross-section at extreme energy. If there exists a Greisen-Zatsepin-Kuz'min (GZK) suppression of cosmic-ray events above EGZK\ensuremath∼5\ifmmode×\else\texttimes\fi1019 eV, as predicted by theory, then the only messengers of energies beyond EGZK are neutrinos. Cosmic neutrino fluxes can initiate air-showers through interaction in the atmosphere, or in the Earth. Neutrino trajectories will be downgoing to nearly horizontal in the former case, and ``Earth-skimming'' in the latter case. Thus it is important to know the acceptances (event rate/flux) of proposed air-shower experiments for detecting both types of neutrino-initiated events. We calculate these acceptances for fluorescence detectors, both space-based as with the EUSO and OWL proposals, and ground-based, as with Auger, HiRes and Telescope Array. The neutrino cross-section \ensuremathσ_\ensuremathνNCC is unknown at energies above 5.2\ifmmode×\else\texttimes\fi1013 eV. Although the popular QCD extrapolation of lower-energy physics offers the cross-section value of 0.54\ifmmode×\else\texttimes\fi10^\ensuremath-31(E_\ensuremathν/1020 eV)0.36 cm2, new physics could raise or lower this value. Therefore, we present the acceptances of horizontal (HAS) and upgoing (UAS) air-showers as a function of \ensuremathσ_\ensuremathνNCC over the range 10^\ensuremath-34 to 10^\ensuremath-30 cm2. The dependences of acceptances on neutrino energy, shower-threshold energy, shower length, and shower column density are also studied. We introduce a cloud layer, and study its effect on rates as viewed from space and from the ground. For UAS, we present acceptances for events over land (rock), and over the ocean (water). Acceptances over water are larger by about an order of magnitude, thus favoring space-based detectors. We revisit the idea of Kusenko and Weiler [Phys. Rev. Lett. 88, 161101 (2002)] to infer \ensuremathσ_\ensuremathνNCC at E_\ensuremathν\ensuremath\gtrsim1020 from the ratio of HAS-to-UAS events, and obtain favorable results. Included in our UAS calculations are realistic energy-losses for taus, and Earth-curvature effects. Most of our calculation is analytic, allowing insight into the various subprocesses that collectively turn an incident neutrino into an observable shower.