07/05/2003 Valencia1 The Ultra-High Energy Cosmic Rays Introduction Data Acceleration and propagation Numerical Simulations (Results) Conclusions Isola Claudia Ecole Polytechnique / IAP- Paris

07/05/2003 Valencia2 Introduction  12 orders of magnitude on the energy and 30 orders on the spectrum  Two cut-off : at the knee and at the ankle (galactic to extragalactic component)  At around 10 9 eV solar origin  Between 10 9 eV and eV Galactic origin (SNR)  Between eV and eV probably Galactic origin but yet unclear  Above eV unknown origin but very probably extra-galactic

07/05/2003 Valencia3 The showers They reveal their existence only by indirect effects Charged hadronic particles, electrons and muons are recorded on the ground particles on the ground 99% electrons (red) and gamma (green) in the MeV energy range 1% muons (blue) in the GeV energy range

07/05/2003 Valencia4 Detection:two techniques The energy of the primary from the particle density at 600m from the shower core; the mass of the primary from  e /   Direct observation of CR primaries is only possible from space Such detectors are limited in size - The highest energies require big surfaces Water Cherenkov or scintillation detectors AGASA Fluorescence detector HiRes The energy of the primary from the quantity of light produced; the mass of primary from the column depth X max They are detected on the ground

07/05/2003 Valencia5 Data Questions: their origin, their nature and where does the spectrum ends? Three quantities: arrival direction, mass of the primary particle, energy of the primary particle The angular distribution, the chemical composition, the spectrum

07/05/2003 Valencia6 The angular distribution Energy in the range (4-10) x10 19 eV  Energy ≥ eV Doublets Triplet Energy in the range (1-4) x10 19 eV

07/05/2003 Valencia7 The chemical composition Fly’s eye data o Theoretical prediction for the iron  Theoretical prediction for protons  Simple two component model Transition from « heavy » to « light » component Transition from galactic to extragalactic origin

07/05/2003 Valencia8 The spectrum AGASA and HIres are not consistent at the highest energies Does a GZK cut-off exist?

07/05/2003 Valencia9 The Pierre Auger Project  A combination of a ground array and one or more fluorescence detectors  Effective aperture about 200 times as large as the AGASA array  1700 particle detectors covering about 3000 Km 2  events per year above eV  It is planned to construct one site in each hemisphere (Argentina and Utah)

07/05/2003 Valencia10 How can they achieve these energies? Decay from a supermassive paticle X Topological defects or metastable particles from inflation Final products:, ,  Statistical acceleration in a magnetized plasma Fermi mechanism Power law spectrum Supernovae, Hot spot of radio galaxies, Actif galactic nuclei Top-DownBottom-Up

07/05/2003 Valencia11 The GZK cut-off Physics beyond the Standard Model? The nucleons interact with the background photons Threshold energy for a photo-pion reaction Energy loss Mean free path

07/05/2003 Valencia12 The cross section for the photo-pion reaction Attenuation lenght

07/05/2003 Valencia13 Few objets as possible sources

07/05/2003 Valencia14 In general we cannot achieve the maximal value E max because of the energy losses at the source from synchrotron radiation and photo-pion reaction

07/05/2003 Valencia15 The angular distribution Two possibilities 1)Many Sources 2)A few sources but a strong magnetic field This could explain the absence of correlation between the arrival direction and powerful astrophysical objects The isotropy at large scale as a diffusion effect The clusters at small scales as a magnetic lensing effects

07/05/2003 Valencia16 The numerical simulation  The purpose  The purpose is to test theoretical models by using a numerical code an extragalactic magnetic field energy losses  The code simulates the propagation of charged particle in an extragalactic magnetic field by taking into account the energy losses  The results are strongly affected by the magnetic field

07/05/2003 Valencia17 The effect of magnetic fields Deflection Time delay Diffusion They affect the angular distribution, the clusters, the spectrum and the chemical composition

07/05/2003 Valencia18 The code We assume a random turbulent magnetic field We use n B =-11/3 ->Kolmogorov turbulence L characterize the coherence length of the magnetic field 5000 trajectories are computed for each magnetic field realization 20 realizations in total Each trajectory is followed for a maximal time of 10 Gyr

07/05/2003 Valencia19 Centaurus A (I) One single source at 3.4 Mpc B=0.3  G

07/05/2003 Valencia20 Centaurus A (II) B=0.3  G B=1  G

07/05/2003 Valencia21 The Local SuperCluster Distribution of sources We take a discrete distribution of sources centered at 20 Mpc from Earth and distributed on a sheet of thickness 3 Mpc and radius 20 Mpc, with the source density following the profile of the shee The auto-correlation function

07/05/2003 Valencia22 Auto-correlation function (I) 100 sources and B=0.05 µG100 sources and B=0.3 µG

07/05/2003 Valencia23 Auto-correlation function (II) 5 sources and B=0.3 µG10 sources and B=0.3 µG

07/05/2003 Valencia24 The spectrum 10 sources and B=0.3 µG E -2 injection spectrum Sources in a sphere of 40 Mpc around the Local Supergalactic center

07/05/2003 Valencia25 Centaurus A (again) Agasa exposure function Auger exposure function

07/05/2003 Valencia26 Heavy nuclei The maximal acceleration energy depends linearly on the charge Ze The deflection is also proportional to the charge Ze Heavy nuclei are attenuated basically by two processes: photodisintegration on the diffuse photon backgrounds and creation of e ± pairs n(  ) is the photon density of the ambient radiation We include the contributions from three different components: infra-red, CMB and Universal Radio Background

07/05/2003 Valencia27 The energy loss time Helium Silicon Carbon Iron At energies above eV the heaviest nuclei start to disintegrate more quickly The multi-nucleon emission becomes more important compared to one or two nucleon emission

07/05/2003 Valencia28 Chemical composition B= G B=2x10 -8 G

07/05/2003 Valencia29 The observed spectra All particle spectrum observed at distances d=1.5, 2.3,3.2,4.8,7.1,10.5,15.5,33.9,50 Mpc (dotted line) B= G B=2x10 -8 G

07/05/2003 Valencia30 Applications Anchordoqui et al. Iron nuclei accelerated in two nearby starbust galaxies. Hard injection spectrum. Ahn et al. UHECR originate from M87, deflected in a powerful galactic magnetic field. The two highest energy events He nuclei.

07/05/2003 Valencia31 Conclusions Many questions are still open on the Ultra High Energy Cosmic Rays Their origin (source and acceleration mechanism), their nature and the end of the spectrum We used a numerical code to simulate some possible scenarios and we were able to ruled out some of the scenarios proposed We plan to implement our code and combine it with the new statistics coming from Auger The very next future years will be crucial to solve this misteryThe very next future years will be crucial to solve this mistery