4,171 research outputs found
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 eV up to 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
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