We report on further SLAC measurements of the Askaryan effect: coherent radio emission from charge asymmetry in electromagnetic cascades. We used synthetic rock salt as the dielectric medium, with cascades produced by GeV bremsstrahlung photons at the Final Focus Test Beam. We extend our prior discovery measurements to a wider range of parameter space and explore the effect in a dielectric medi...

Owing to their isotropy, it is generally believed that ultrahigh energy cosmic rays (UHECRs) are extragalactic in origin. It is then expected that interactions of these cosmic rays with photons of the cosmic background radiation (CBR) should produce a drastic reduction in their flux above and energy of about 5×1019 eV (50 EeV), the so-called “GZK effect”. At present, the existence of this effec...

If there exists the mirror world, a parallel hidden sector of particles with exactly the same microphysics as that of the observable particles, then the primordial nucleosynthesis constraints require that the temperature of the cosmic background of mirror relic photons should be smaller than that of the ordinary relic photons, T /T < 0.5 or so. On the other hand, the present experimental and as...

We study the extragalactic protons with universal spectrum, which is independent of mode of propagation, when distance between sources is less than the propagation lengths, such as energy attenuation length or diffusion length (for propagation in magnetic fields). The propagation features in this spectrum, the GZK cutoff, dip and bump, are studied with help of modification factor, which weakly ...

There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn off photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the sp...

We conjecture that the highest energy cosmic rays, E > E GZK , where E GZK ∼ 5 · 10 19 eV is the Greisen–Zatsepin–Kuzmin cutoff energy of cosmic ray spectrum, may provide a unique window into the very early epoch of the Universe, namely, that of reheating after inflation, provided these cosmic rays are due to decays of parent superheavy long-living X-particles. These particles may constitute a ...

The origin of the highest energy cosmic rays at ∼1020 eV is still unknown. Ultra-high energy neutrinos from the GZK process should provide information on the sources and their properties. A promising and cost effective method for observing GZKneutrinos is based on detection of Askaryan radio pulses with antennas installed in ice. The ARIANNA project aims at instrumenting a 36*36 km2 large area ...