Prospect of determining the Dirac/Majorana state of neutrino by Multi-OWL experiment

We consider the non-radiative two body decay of a neutrino to a daughter neutrino with degraded energy and a very light particle (Majoron). Ultrahigh energy neutrinos from an astrophysical source like a Gamma Ray Burst undergoing this decay process are found to produce different number of events in the detector depending on whether they are Majorana or Dirac particles. The next generation large scale experiments like Multi-OWL is expected to provide us an accurate determination of the flux of neutrinos from astrophysical sources and this may enable us to distinguish between the Dirac and Majorana nature of neutrino.Comment: 18 pages latex, no figure. Journal of Phys. G in pres

Cosmic Physics: The High Energy Frontier

Cosmic rays have been observed up to energies $10^8$ times larger than those of the best particle accelerators. Studies of astrophysical particles (hadrons, neutrinos and photons) at their highest observed energies have implications for fundamental physics as well as astrophysics. Thus, the cosmic high energy frontier is the nexus to new particle physics. This overview discusses recent advances being made in the physics and astrophysics of cosmic rays and cosmic gamma-rays at the highest observed energies as well as the related physics and astrophysics of very high energy cosmic neutrinos. These topics touch on questions of grand unification, violation of Lorentz invariance, as well as Planck scale physics and quantum gravity.Comment: Topical Review Paper to be published in the Journal of Physics G, 50 page

The Particle Physics Reach of High-Energy Neutrino Astronomy

We discuss the prospects for high-energy neutrino astronomy to study particle physics in the energy regime comparable to and beyond that obtainable at the current and planned colliders. We describe the various signatures of high-energy cosmic neutrinos expected in both neutrino telescopes and air shower experiments and discuss these measurements within the context of theoretical models with a quantum gravity or string scale near a TeV, supersymmetry and scenarios with interactions induced by electroweak instantons. We attempt to access the particle physics reach of these experiments.Comment: Mini-review article for New Journal of Physics, "Focus on Neutrinos" issue. 27 pages, 11 figure

Ultra-High Energy Neutrino Fluxes: New Constraints and Implications

We apply new upper limits on neutrino fluxes and the diffuse extragalactic component of the GeV gamma-ray flux to various scenarios for ultra high energy cosmic rays and neutrinos. As a result we find that extra-galactic top-down sources can not contribute significantly to the observed flux of highest energy cosmic rays. The Z-burst mechanism where ultra-high energy neutrinos produce cosmic rays via interactions with relic neutrinos is practically ruled out if cosmological limits on neutrino mass and clustering apply.Comment: 10 revtex pages, 9 postscript figure

High-energy Neutrino Astronomy: The Cosmic Ray Connection

This is a review of neutrino astronomy anchored to the observational fact that Nature accelerates protons and photons to energies in excess of $10^{20}$ and $10^{13}$ eV, respectively. Although the discovery of cosmic rays dates back close to a century, we do not know how and where they are accelerated. Basic elementary-particle physics dictates a universal upper limit on their energy of $5\times10^{19}$ eV, the so-called Greisen-Kuzmin-Zatsepin cutoff; however, particles in excess of this energy have been observed by all experiments, adding one more puzzle to the cosmic ray mystery. Mystery is fertile ground for progress: we will review the facts as well as the speculations about the sources including gamma ray bursts, blazars and top-down scenarios. The important conclusion is that, independently of the specific blueprint of the source, it takes a kilometer-scale neutrino observatory to detect the neutrino beam associated with the highest energy cosmic rays and gamma rays. We also briefly review the ongoing efforts to commission such instrumentation.Comment: 83 pages, 18 figures, submitted to Reports on Progress in Physic