Ultrahigh Energy Cosmic Rays: Facts, Myths, and Legends

This is a written version of a series of lectures aimed at graduate students in astrophysics/particle theory/particle experiment. In the first part, we explain the important progress made in recent years towards understanding the experimental data on cosmic rays with energies > 10^8 GeV. We begin with a brief survey of the available data, including a description of the energy spectrum, mass composition, and arrival directions. At this point we also give a short overview of experimental techniques. After that, we introduce the fundamentals of acceleration and propagation in order to discuss the conjectured nearby cosmic ray sources, and emphasize some of the prospects for a new (multi-particle) astronomy. Next, we survey the state of the art regarding the ultrahigh energy cosmic neutrinos which should be produced in association with the observed cosmic rays. In the second part, we summarize the phenomenology of cosmic ray air showers. We explain the hadronic interaction models used to extrapolate results from collider data to ultrahigh energies, and describe the prospects for insights into forward physics at the Large Hadron Collider (LHC). We also explain the main electromagnetic processes that govern the longitudinal shower evolution. Armed with these two principal shower ingredients and motivation from the underlying physics, we describe the different methods proposed to distinguish primary species. In the last part, we outline how ultrahigh energy cosmic ray interactions can be used to probe new physics beyond the electroweak scale.Comment: Lectures given at the 6th CERN-Latin-American School of High-Energy Physics, Natal, Brazil, March - April, 2011. (92 pages, 37 figures) Submitted for publication in a CERN Yellow Report. http://physicschool.web.cern.ch/PhysicSchool/CLASHEP/CLASHEP2011/

Wormholes in spacetime with torsion

Analytical wormhole solutions in U4 theory are presented. It is discussed whether the extremely short range repulsive forces, related to the spin angular momentum of matter, could be the "carrier" of the exoticity that threads the wormhole throat.Facultad de Ciencias Exacta

Neutrino Cosmology after WMAP and LHC7

The gauge-extended U(1)_C \times SU(2)_L \times U(1)_{I_R} \times U(1)_L model has the attractive property of elevating the two major global symmetries of the standard model (baryon number B and lepton number L) to local gauge symmetries. The U(1)_L symmetry prevents the generation of Majorana masses, leading to three superweakly interacting right-handed neutrinos. This also renders a B-L symmetry non-anomalous. We show that the superweak interactions of these Dirac states (through their coupling to the TeV-scale B-L gauge boson) permit right-handed neutrino decoupling just above the QCD phase transition: 175 MeV < T_{\nu_R}^{dec} < 250 MeV. In this transitional region, the residual temperature ratio between \nu_L and \nu_R generates extra relativistic degrees of freedom at BBN and at the CMB epochs. Consistency (within 1\sigma) with both WMAP 7-year data and the most recent estimate of the primordial ^4He mass fraction is achieved for 3 TeV < M_{B-L} < 6 TeV. The model is fully predictive, and can be confronted with dijet and dilepton data (or lack thereof) from LHC7 and, eventually, LHC14.Comment: References added; to be published in PR

Extensive air showers rounded up by AIRES + SIBYLL/QGS

An analysis of the differences introduced by the hadronic interaction event generators during the development of the showers is presented. We have generated proton and nuclei induced air showers with energies up to 1020.5 eV, “herded up” by the code AIRES + SIBYLL/QGSJET. The most relevant observables are taken into account for the comparison.Facultad de Ciencias Exacta

Possible test of local Lorentz invariance from τ decays

We analyze the possibility of testing local Lorentz invariance from the observation of tau decays. Future prospects of probing distances below the electroweak characteristic scale are discussed.Artículo enviado a Zeitschrift für Physik CFacultad de Ciencias Exacta

Possible test of local Lorentz invariance from τ decays

We analyze the possibility of testing local Lorentz invariance from the observation of tau decays. Future prospects of probing distances below the electroweak characteristic scale are discussed.Artículo enviado a Zeitschrift für Physik CFacultad de Ciencias Exacta

Opacity of the microwave background radiation to ultrahigh energy cosmic rays

In this work we re-examine the influence of the microwave background radiation on the propagation of extremely high energy cosmic rays. We present a recalculation of the rate of fractional energy loss in the continuous energy loss approximation including the effects of resonances other than the Δ. We also discuss the distortion of the cosmic ray spectrum due to interactions with the relic photons.Facultad de Ciencias Exacta