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Register a new userThe Highest Energy Cosmic Rays and Particle Physics
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It has been argued that the observations of cosmic particles with energies in excess of $10^8$ TeV represent a puzzle. Its solution requires new astrophysics or new particle physics. We show that the latter is unlikely given that the scale associated with a new particle physics threshold must be of order 1 GeV, not TeV and above, in order to resolve the problem. In most cases such new physics should have been revealed by accelerator experiments. We examine the possibility that the highest energy cosmic rays are initiated by non-standard interactions of neutrinos in the atmosphere. We show that proposals in this direction either violate s-wave unitarity or fall short of producing a sizeable effect by several orders of magnitude.
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Observation of Ultra High Energy Cosmic Rays (UHECR) -whose energy exceeds $10^20$eV- is still a puzzle for modern astrophysics. The transfer of more than 16 Joules to a microscopic particle can hardly be achieved, even in the most powerful cosmic accelerators such as AGNs, GRBs or FR-II radio galaxy lobes. Potential sources must also lie within 100 Mpc of the Earth as the interaction length of protons, nuclei or photons is less than 10Mpc. However no visible counterpart of those sources has been observed. Calling upon new physics such as Topological Defect interactions or Super Massive Relic Particle decays is therefore very tempting, but such objects are yet to be proven to exist. Due to the very low flux of UHECR only very large dedicated experiments, such as the Auger observatories, will allow to shed some light on the origin of those cosmic rays. In this quest neutrinos, if they can be detected, are an invaluable messengers of the nature of the sources.
Introducing a simple Galactic wind model patterned after the solar wind we show that back-tracing the orbits of the highest energy cosmic events suggests that they may all come from the Virgo cluster, and so probably from the active radio galaxy M87. This confirms a long standing expectation. Those powerful radio galaxies that have their relativistic jets stuck in the interstellar medium of the host galaxy, such as 3C147, will then enable us to derive limits on the production of any new kind of particle, expected in some extensions of the standard model in particle physics. New data from HIRES will be crucial in testing the model proposed here.
Here in this lecture we will touch on two aspects, one the new radio methods to observe the effects of high energy particles, and second the role that radio galaxies play in helping us understand high energy cosmic rays. We will focus here on the second topic, and just review the latest developments in the first. Radio measurements of the geosynchrotron radiation produced by high energy cosmic ray particles entering the atmosphere of the Earth as well as radio v{C}erenkov radiation coming from interactions in the Moon are another path; radio observations of interactions in ice at the horizon in Antarctica is a related attempt. Radio galaxy hot spots are prime candidates to produce the highest energy cosmic rays, and the corresponding shock waves in relativistic jets emanating from nearly all black holes observed. We will review the arguments and the way to verify the ensuing predictions. This involves the definition of reliable samples of active sources, such as black holes, and galaxies active in star formation. The AUGER array will probably decide within the next few years, where the highest energy cosmic rays come from, and so frame the next quests, on very high energy neutrinos and perhaps other particles.
One of several working groups established for this workshop was charged with examining results and methods associated with the UHECR energy spectrum. We summarize the results of our discussions, which include a better understanding of the analysis choices made by groups and their motivation. We find that the energy spectra determined by the larger experiments are consistent in normalization and shape after energy scaling factors are applied. Those scaling factors are within systematic uncertainties in the energy scale, and we discuss future work aimed at reducing these systematics.
We examine the anisotropy of the arrival directions of twenty seven ultra high energy cosmic rays detected by the Pierre Auger Collaboration. We confirm the anisotropy of the arrival directions of these events and find a significant correlation with the updated definition of the supergalactic plane at distances up to 70 Mpc, A Monte Carlo calculation of isotropic source distribution suggests a chance probability for isotropic event arrival direction distribution of 2-6$times10^{-4}$.
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