ar X iv : a st ro - p h / 99 02 18 7 v 1 1 2 Fe b 19 99

Abstract

Neutrinos are one of the least explored fundamental sectors of the Standard Model because they have a challenging low cross section. Besides man made nuclear reactions and beam dump experiments in accelerators, neutrinos have only been detected from two astrophysical sources: the Sun 1 and supernova SN 1987A and from the interactions of cosmic rays with the atmosphere . Their potential for fundamental research is however large as illustrated by the few events from SN 1987A and the recent evidence for flavor oscillations, completing the Standard Model and providing clues for physics beyond. Moreover they have an unique Astronomy potential as they can travel unattenuated through matter shields that are opaque to other types of radiation. The neutrino nucleon cross section rises with energy, first linearly and then more slowly because of the low x behavior of the parton distributions, so that the Earth becomes opaque for neutrinos of Eν ∼ 100 TeV, with relevant implications for detection techniques. In this article we will concentrate on neutrinos above the EeV energy scale with an expected cross section in the 10-100 nb range. Existing neutrino detectors as well as those in construction or planning have motivated estimates of neutrino fluxes from many possible sources such as Active Galactic Nuclei (AGN) cores 6 and jets , Gamma Ray Bursts (GRB) 8 and decays of Topological Defects (TD) . These calculations extend to energies in the EeV range with fluxes that are however quite uncertain because AGN and GRB are not well understood and the TD densities and annihilation rates are quite unknown. There are however better established neutrino fluxes from beam dumps in which cosmic rays interact with matter in the Universe, either the galactic disk, molecular clouds or the Earth atmosphere. Below 100 TeV atmospheric neutrinos are subject to uncertainties in the 20% range 10 but above these uncertainties become larger because prompt decays from charm production dominates. The establishment of cosmic rays above the Greisen-Zatsepin-Kuz’min (GZK) cutoff (∼ 6 10 eV) 11 and the absorption of protons and nuclei in the Cosmic Microwave Background (CMB), guarantees

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Cite this paper

@inproceedings{Neutrinos1999arXI, title={ar X iv : a st ro - p h / 99 02 18 7 v 1 1 2 Fe b 19 99}, author={EeV Neutrinos and Jaime Alvarez-Mu{\~n}iz}, year={1999} }