Ultra-High Energy Cosmic Rays

The origin of the ultra high energy cosmic rays (UHECR) with energies above E > 1017eV, is still unknown. The discovery of their sources will reveal the engines of the most energetic astrophysical accelerators in the universe. This is a written version of a series of lectures devoted to UHECR at the 2013 CERN-Latin-American School of High-Energy Physics. We present an introduction to acceleration mechanisms of charged particles to the highest energies in astrophysical objects, their propagation from the sources to Earth, and the experimental techniques for their detection. We also discuss some of the relevant observational results from Telescope Array and Pierre Auger Observatory. These experiments deal with particle interactions at energies orders of magnitude higher than achieved in terrestrial accelerators.Comment: 22 pages, contribution to the 2013 CERN - Latin-American School of High-Energy Physics, Arequipa, Peru, 6-19 Mar 201

Phenomenology of cosmic ray air showers

The properties of cosmic rays with energies above 1PeV have to be deduced from the spacetime structure and particle content of the air showers which they initiate. In this review, a summary of the phenomenology of these giant air showers is presented. We describe the hadronic interaction models used to extrapolate results from collider data to ultra high energies, an also the main electromagnetic processes that govern the longitudinal shower evolution as well as the lateral spread of particles.Comment: Invited talk at the Fifth International Workshop on New Worlds in Astroparticle Physics, 8-10 January 2005, Faro, Portugal (http://www.ualg.pt/fct/fisica/centra/a2005.html). Based on the review article Annals Phys. 314:145-207, 2004. Typo in the labelling of Fig.2 correcte

Determination of the Higgs boson spin with a linear e+e- collider

The energy dependence of the production cross section of a light Higgs boson is studied at threshold and compared to the expectations of several spin assumptions. Cross section measurements at three centre-of-mass energies with an integrated luminosity of 20 fb-1 allow the confirmation of the scalar nature of the Higgs Boson.Comment: 4 pages (Latex), 4 figures (Postscript

Cosmic-ray physics and the Pierre Auger Observatory

One of the foremost issues in astrophysics today is that of the origin of ultrahigh- energy cosmic rays. The Pierre Auger Observatory is a broadly based international effort to make a high-statistics study of the upper-end of the cosmic-ray spectrum. Auger is the rst experiment designed to work in a hybrid detection mode. It consists of an array of 1600 particle detectors spread over 3000 km2 and four uorescence telescopes placed on the boundaries of the surface array. Recent measurements from Auger of the energy spectrum and mass composition above 1018 eV are described

Massive relic neutrinos in the galactic halo and the knee in the cosmic ray spectrum

Despite many efforts to find a reasonable explanation, the origin of the "knee" in the cosmic ray spectrum at energy around 10**15.5 eV remains mysterious. In this letter we suggest that the "knee" may be due to a GZK-like effect of cosmic rays interacting with massive neutrinos in the galactic halo. Simple kinematics connects the location of the "knee" with the mass of the neutrinos, and, while the required interaction cross section is larger than that predicted by the Standard Model, it can be accommodated by a small neutrino magnetic dipole moment. The values for the neutrino parameters obtained from the analysis of existing experimental data are compatible with present laboratory bounds.Comment: 8 pages, 1 figure, uses RevTe

Hinting at primary composition using asymmetries in time distributions

Evidence of azimuthal asymmetries in the time structure and signal size have been found in non-vertical showers at the Pierre Auger Observatory. It has been previously shown that the asymmetry in time distributions offers a new possibility for the determination of the mass composition. New studies have demonstrated that the dependence of the asymmetry parameter in the rise-time and fall-time distributions with sec(theta) shows a clear peak. Both, the position of the peak, X_asymax, and the size of the asymmetry at X_asymax are sensitive to primary mass composition and have a small dependence on energy. In this paper a study of the discriminating power of the new observables to separate primary species is presented.Comment: To be published in the Proceedings of 29th International Cosmic Ray Conference (ICRC 2005), Pune, India, August 3-10, 200

Hadronic interactions models beyond collider energies

Studies of the influence of different hadronic models on extensive air showers at ultra-high energies are presented. The hadronic models considered are those implemented in the well-known QGSJET and SIBYLL event generators. The different approaches used in both codes to model the underlying physics is analyzed using computer simulations performed with the program AIRES. The most relevant observables for both single collisions and air showers are studied for primary energies ranging from $10^{14}$ eV up to $10^{20.5}$ eV. In addition, the evolution of lateral and energy distributions during the shower development is presented. Our analysis seems to indicate that the behaviour of shower observables does not largely reflect the strong differences observed in single collisions.Comment: 31 RevTex pages - 14 ps figure