Measurement of the energy spectrum of cosmic rays using the Pierre Auger Observatory

The flux of cosmic rays above 1018 eV has been measured with unprecedented precision at the Pierre Auger Observatory. Two analysis techniques have been used to extend the spectrum downwards from 3×1018 eV, with the lower energies being explored using a unique technique that exploits the hybrid strengths of the instrument. The spectral features are also presented

Propagation of UHECRs in cosmological backgrounds: some results from SimProp

Ultra-High-Energy Cosmic Ray (UHECR) nuclei propagating in cosmological radiation backgrounds produce secondary particles detectable at Earth. SimProp is a one dimensional code for extragalactic propagation of UHECR nuclei, inspired by the kinetic approach of Aloisio et al. As in this approach, only a subset of nuclei and nuclear channels are used as representative. We discuss the validation of the code and present applications to UHECR experimental results. In particular we present the expected fluxes of neutrinos produced in some astrophysical scenario.Comment: Poster presented by A. Di Matteo at the 33rd International Cosmic Ray Conference, Rio De Janeiro (Brasil) July 2-9 201

Cosmogenic neutrinos and ultra-high energy cosmic ray models

We use an updated version of {\it SimProp}, a Monte Carlo simulation scheme for the propagation of ultra-high energy cosmic rays, to compute cosmogenic neutrino fluxes expected on Earth in various scenarios. These fluxes are compared with the newly detected IceCube events at PeV energies and with recent experimental limits at EeV energies of the Pierre Auger Observatory. This comparison allows us to draw some interesting conclusions about the source models for ultra-high energy cosmic rays. We will show how the available experimental observations are almost at the level of constraining such models, mainly in terms of the injected chemical composition and cosmological evolution of sources. The results presented here will also be important in the evaluation of the discovery capabilities of the future planned ultra-high energy cosmic ray and neutrino observatories.Comment: 15 pages, 8 figures, some reference added, version accepted for publication in JCA

Detection of GRB signals with Fluorescence Detectors

Gamma Ray Bursts are being searched in many ground based experiments detecting the high energy component (GeV $\div$ TeV energy range) of the photon bursts. In this paper, Fluorescence Detectors are considered as possible candidate devices for these searches. It is shown that the GRB photons induce fluorescence emission of UV photons on a wide range of their spectrum. The induced fluorescence flux is dominated by GRB photons from 0.1 to about 100 MeV and, once the extinction through the atmosphere is taken into account, it is distributed over a wide angular region. This flux can be detected through a monitor of the diffuse photon flux, provided that its maximum value exceeds a threshold value, that is primarily determined by the sky brightness above the detector. The feasibility of this search and the expected rates are discussed on the basis of the current GRB observations and the existing fluorescence detectors.Comment: 16 pages 9 eps figure

Testing Lorentz invariance violation using cosmogenic neutrinos

Secondary messengers such as neutrinos and photons are expected to be produced in interactions of ultra-high-energy cosmic rays (UHECRs) with extragalactic background photons. Their propagation could be altered by the effects of Lorentz invariance violation. In this work, we have developed an extension of the SimProp code that includes some Lorentz-violating scenarios affecting the propagation of neutrinos. We present the corresponding expected cosmogenic neutrino fluxes for three different astrophysical scenarios for the production of UHECRs. These results can be used to put constraints on the scale of Lorentz violation in the neutrino sector.Comment: 8 pages. Proceedings for the 38th International Cosmic Ray Conference (ICRC) 202

Ultra High Energy Cosmic Rays: Anisotropies and Spectrum

The recent results of the Pierre Auger Observatory on the possible correlation of Ultra High Energy Cosmic Rays events and several nearby discrete sources could be the starting point of a new era with charged particles astronomy. In this paper we introduce a simple model to determine the effects of any local distribution of sources on the expected flux. We consider two populations of sources: faraway sources uniformly distributed and local point sources. We study the effects on the expected flux of the local distribution of sources, referring also to the set of astrophysical objects whose correlation with the Auger events is experimentally claimed.Comment: 17 pages, 13 eps figures, version accepted for publication in Astroparticle Physic

SimProp: a Simulation Code for Ultra High Energy Cosmic Ray Propagation

A new Monte Carlo simulation code for the propagation of Ultra High Energy Cosmic Rays is presented. The results of this simulation scheme are tested by comparison with results of another Monte Carlo computation as well as with the results obtained by directly solving the kinetic equation for the propagation of Ultra High Energy Cosmic Rays. A short comparison with the latest flux published by the Pierre Auger collaboration is also presented.Comment: 19 pages, 12 eps figures, version accepted for publication in JCA