Neutrinos as a Diagnostic of High Energy Astrophysical Processes

A leading candidate for the extragalactic source of high energy cosmic rays is the Fermi engine mechanism, in which protons confined by magnetic fields are accelerated to very high energy through repeated scattering by plasma shock fronts. In the process of acceleration, collisions of trapped protons with the ambient plasma produce pions which decay to electromagnetic energy and neutrinos. For optically thin sources, a strong connection between the emerging cosmic rays and secondary neutrinos can be established. In this context, we show the feasibility of using the Glashow resonance as a discriminator between the $pp$ and $p\gamma$ interactions in Fermi engines as sources of neutrinos. In particular, we demonstrate how three years of observation at the km$^3$ IceCube facility can serve as a filter for the dominance of the $pp$ interaction at the source.Comment: The previous version of this paper contained a brief discussion of how the flux of neutrinos from optically thin sources can be used as a marker of the cosmic ray Galactic/extra-galactic transition. This topic has received detailed discussion in a separate paper, arXiv:astro-ph/050322

Probing QCD approach to thermal equilibrium with ultrahigh energy cosmic rays

The Pierre Auger Collaboration has reported an excess in the number of muons of a few tens of percent over expectations computed using extrapolation of hadronic interaction models tuned to accommodate LHC data. Very recently, we proposed an explanation for the muon excess assuming the formation of a deconfined quark matter (fireball) state in central collisions of ultrarelativistic cosmic rays with air nuclei. At the first stage of its evolution the fireball contains gluons as well as $u$ and $d$ quarks. The very high baryochemical potential inhibits gluons from fragmenting into $u \bar u$ and $d \bar d$, and so they fragment predominantly into $s \bar s$ pairs. In the hadronization which follows this leads to the strong suppression of pions and hence photons, but allows heavy hadrons to be emitted carrying away strangeness. In this manner, the extreme imbalance of hadron to photon content provides a way to enhance the muon content of the air shower. In this communication we study theoretical systematics from hadronic interaction models used to describe the cascades of secondary particles produced in the fireball explosion. We study the predictions of one of the leading LHC-tuned models QGSJET II-04 considered in the Auger analysis.Comment: 7 pages LaTeX, 6 .pdf figure

Sensitivity of orbiting JEM-EUSO to large-scale cosmic-ray anisotropies

The two main advantages of space-based observation of extreme-energy ($\gtrsim 10^{19}$~eV) cosmic-rays (EECRs) over ground-based observatories are the increased field of view, and the all-sky coverage with nearly uniform systematics of an orbiting observatory. The former guarantees increased statistics, whereas the latter enables a partitioning of the sky into spherical harmonics. We have begun an investigation, using the spherical harmonic technique, of the reach of \J\ into potential anisotropies in the extreme-energy cosmic-ray sky-map. The technique is explained here, and simulations are presented. The discovery of anisotropies would help to identify the long-sought origin of EECRs.Comment: 7 pages, 6 figures. To appear in the proceedings of the Cosmic Ray Anisotropy Workshop, Madison Wisconsin, September 201