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Title: Acceptances for space-based and ground-based fluorescence detectors, and inference of the neutrino-nucleon cross-section above 10{sup 19} eV

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 E{sub GZK}{approx}5x10{sup 19} eV, as predicted by theory, then the only messengers of energies beyond E{sub GZK} 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 {sigma}{sub {nu}}{sub N}{sup CC} is unknown at energies above 5.2x10{sup 13} eV. Although the popular QCD extrapolation of lower-energy physics offers the cross-section value of 0.54x10{sup -31}(E{sub {nu}}/10{sup 20} eV){sup 0.36} cm{sup 2}, 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 {sigma}{sub {nu}}{submore » N}{sup CC} over the range 10{sup -34} to 10{sup -30} cm{sup 2}. 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 {sigma}{sub {nu}}{sub N}{sup CC} at E{sub {nu}} > or approx. 10{sup 20} 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.« less
Authors:
; ;  [1]
  1. Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235-1807 (United States)
Publication Date:
OSTI Identifier:
20782864
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 8; Other Information: DOI: 10.1103/PhysRevD.73.083003; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COSMIC NEUTRINOS; COSMIC RAY DETECTION; COSMIC SHOWERS; CROSS SECTIONS; EEV RANGE; ENERGY LOSSES; ENERGY SPECTRA; EXTRAPOLATION; FLUORESCENCE; NEUTRINO DETECTION; NEUTRINO-NUCLEON INTERACTIONS; NUCLEONS; QUANTUM CHROMODYNAMICS; THRESHOLD ENERGY; UNIVERSE; WATER