Cosmic rays of energies larger than the Greisen-Zatsepin-Kuzmin (GZK) cutoff may be neutrinos if they acquire strong interactions due to a "precocious unification" of forces. A scenario for this to happen is outlined. There is no contradiction with precision measurements carried out at LEP and SLAC. Observable consequences at LHC and future neutrino detectors are discussed.PACS 13.85.T, 13.15, 14.60.S A substantial number of cosmic ray events has been detected in which the primary energy appears to exceed the Greisen-Zatsepin-Kuzmin (GZK) cutoff, see e.g. [1, 2, 3, 4] and Szabelski's recent review [5]. The onset of the GZK cutoff itself is somewhat uncertain: the energy of the rapid turnover of the spectrum depends on several details (for instance, on the injection spectrum, etc. ), see ref.[6] for a modern treatment. Nevertheless, it is unlikely that all the events reported can be explained by fluctuations in the shower

The interaction of ultra-high-energy (UHE) cosmic rays with baryonic matter in the Milky Way produces hadrons which ultimately decay into neutrinos. This mnstitutes a backp u n d for neutrino t e l e s m p attempting to discover UHE neutrino point sources in the sky. We give an estimate of this backpund. If there exists a galactic halo of -ONC dark matter, one may be able to use the technique of registering the galactic neutrino backsound to detennine ita distribution.

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that pemZ"O is about one third of pemr-I. However, if, as has been discussed by Pais and Treiman,20 the soft-pion techniques are valid a t q2--MW2, then we can extract the isovector contribution p,,r-1(q2) directly from ex-~eriments. The Dresence of an isoscalar contribution can easily be incorporated into our results.A sizable branching ratjo makes possible the search for the IVB through its hadronic decay modes. Our estimates imply that about half of the W events will decay into hadrons. The background from inelastic neutrino-nucleon scattering, discussed by Cline, Mann, and Rubbia." is still manageable. because a com~leteWe construct a resonance model of deep-inelastic electron scattering. Using semiempirical rules for the form of the nucleon spectrum and a universality hypothesis for the transition form factors, we obtain explicit expressions for the structure functions W1 and W2 in the Bjorken limit. The ratio of the longitudinal to transverse photoabsorption cross sections vanishes for large momentum transfers, and vWz becomes scale invariant. A one-parameter fit is obtained to VWZ (proton), and a zero-parameter prediction is made of vW2 (proton)-vWz (neutron). There is good agreement between the theory and experiment in the region where scale invariance is well established.' J. D. Bjorken, Phys. Rev. 179, 1547 (1969. 2 J. D. Bjorken and E. A. Paschos, Phys. Rev. 185, 1975 (1969). the data is scale i~zvariance, i.e., that the structure func- R, P. Feynman, Phys, Rev, Letters 23, 1415 (1969). tions essentially depend on the ratio v/q2 only, where v S. D. Drell, D. J. Levy, and T. M. Yan, Phys. Rev. Letters is the energy loss of the electron, and q2 is the invariant 22, 744 6 J. J. Sakurai, Phys. Rev. Letters 22, 981 (1969). momentum transfer squared. 6 H. Harari, Phys. Rev. Letters 22, 1978 (1969).

This report was prepared as an account of work sponsored by an agency of the United States Government. Neilher lhc United 3talcs Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or encePr°cessdiscl°sed'°rrepresents that its use w°uld n°t infringe privately°wned rights' Refer" ''' ASSE _ herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endu, sement, recommendation, or favoring by tt:e United States Government or any agenc)thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the "/i united _tates Guwiniiiclit or any agency ,her_,mf ,.-9

X-ray binary systems are expected to emit ultrahigh-energy photons and neutrinos in comparable numbers. Energies of several TeV in the center-of-mass frame in collisions with air nuclei are likely to be present in such beams. These beams can be used to probe the substructure of leptons and quarks by means not available in accelerator-based experiments in the forseeable future. In composite models with leptons and quarks sharing some strongly interacting subconstituents, an increased neutrino interaction cross section is expected above a certain critical energy. Such models lead to some characteristic signatures of the onset of "new physics." Some experiments are proposed to observe the new physics and to test whether the new types of events are caused by neutrinos.

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The deformed Poincaré group contains a characteristic mass, κ. At energies exceeding κ, deviations from the special theory of relativity become significant. However, small deviations from ordinary relativistic kinematics are observable even at energies substantially lower than κ. The observation of distant events producing ultra high energy (UHE) particles leads to a lower limit on κ. From an analysis of the UHE data on the burst in the binary system HER X1 in 1986, we deduce κ > ∼1012 GeV.