The Pierre Auger Observatory

One of the foremost issues in astrophysics today is that of the origin of the ultra high energy cosmic rays. The Pierre Auger Observatory (PAO), currently under construction in the Province of Mendoza, Argentina, is a broadly based international effort to make a high statistic study of the upper-end of the cosmic ray spectrum. The PAO is the first experiment designed to work in a hybrid detection mode. It consists of an array of 1600 particle detectors spread over 3000 km2 and four fluorescence telescopes placed on the boundaries of the surface array. The concept of the experiment as well as the current status and future prospects are presented.Facultad de Ciencias Exacta

The Pierre Auger Observatory

One of the foremost issues in astrophysics today is that of the origin of the ultra high energy cosmic rays. The Pierre Auger Observatory (PAO), currently under construction in the Province of Mendoza, Argentina, is a broadly based international effort to make a high statistic study of the upper-end of the cosmic ray spectrum. The PAO is the first experiment designed to work in a hybrid detection mode. It consists of an array of 1600 particle detectors spread over 3000 km2 and four fluorescence telescopes placed on the boundaries of the surface array. The concept of the experiment as well as the current status and future prospects are presented.Facultad de Ciencias Exacta

The Lorentz structure of semi-hadronic tau decays

Semi‐hadronic tau decays provide a powerful tool to study the Lorentz structure of the weak charged current. Using decays of the τ into a1 it is possible to extract tau polarization Pτ and tau neutrino helicity γVA. A method is presented to determine the tau neutrino helicity independent of any tau polarization which may be present.Facultad de Ciencias Exacta

Future directions in astroparticle physics and the Auger experiment

The observation of cosmic ray particles with unexpected high energies is pushing astroparticle physics into a period of rapid progress both theoretically and experimentally. Different proposed models for the generation of these particles are constrained by the absence of the predicted GZK cutoff in the cosmic ray spectrum and by the composition and the distribution of arrival directions observed. The database increase due to the Pierre Auger Observatory will provide a clearer picture of the spectral anisotropy and properties of such high energy particles, enabling tests of their origin and nature.Facultad de Ciencias Exacta

TESLA - The Superconducting Electron Positron Linear Collider with an Integrated X-Ray Laser Laboratory. Technical Design Report : Part III - Physics at an e+e- Linear Collider

The Standard Model of particle physics was built up through decades of intensive dialogue between theory and experiments at both hadron and electron machines. It has become increasingly coherent as experimental analyses have established the basic physical concepts. Leptons and quarks were discovered as the fundamental constituents of matter. The photon, the W and Z bosons, and the gluons were identified as the carriers of the electromagnetic, weak and strong forces. Electromagnetic and weak forces have been unified within the electroweak gauge field theory. The QCD gauge field theory has been confirmed as the theory of strong interactions.La lista completa de autores del reporte puede verse en la página 6 del documento.Facultad de Ciencias Exacta

Phenomenology of cosmic ray air showers

The properties of cosmic rays with energies above 106 GeV 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.Facultad de Ciencias Exacta

Trigger and aperture of the surface detector array of the Pierre Auger Observatory

The surface detector array of the Pierre Auger Observatory consists of 1600 water-Cherenkov detectors, for the study of extensive airshowers (EAS) generated by ultra-high-energy cosmic rays. We describe the trigger hierarchy, from the identification of candidates howers at the level of a single detector, amongst a large background (mainly random single cosmic ray muons), up to the selection of real events and the rejection of random coincidences. Such trigger makes the surface detector array fully efficient for the detection of EAS with energy above 3 x 1018 eV, for all zenith angles between 03 and 603, independently of the position of the impact point and of the mass of the primary particle. In the serange of energies and angles, the exposure of the surface array can be determined purely on the basis of the geometrical acceptance.La lista completa de autores puede consultarse en el documento o en la página web de la revista.Facultad de Ciencias Exacta

Measurement of η′(958) formation in two-photon collisions at LEP1

The formation of the η′ in the reaction e+e−→e+e−η′→e+e−π+π−γ has been measured by the L3 detector at a centre-of-mass energy of 91 GeV. The radiative width of the η′ has been found to be Γγγ=4.17±0.10(stat.)±0.27(sys.)keV. The Q2 dependence of the η′ formation cross section has been measured for Q2≤10GeV2 and the η′ electromagnetic transition form factor has been determined. The form factor can be parametrised by a pole form with Λ=0.900±0.046(stat.)±0.022(sys.)GeV. It is also consistent with recent non-perturbative QCD calculations.Facultad de Ciencias Exacta

Search for charged Higgs bosons at LEP

A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at centre-ofmass energies between 189 and 209 GeV, corresponding to an integrated luminosity of 629.4 pb−1. Decays into a charm and a strange quark or into a tau lepton and its neutrino are considered. No significant excess is observed and lower limits on the mass of the charged Higgs boson are derived at the 95% confidence level. They vary from 76.5 to 82.7 GeV, as a function of the H±→τν branching ratio.Facultad de Ciencias Exacta

Standard model Higgs boson with the L3 experiment at LEP

Final results of the search for the standard model Higgs boson are presented for the data collected by the L3 detector at LEP at centre-of-mass energies up to about 209 GeV. These data are compared with the expectations of standard model processes for Higgs boson masses up to 120 GeV. A lower limit on the mass of the standard model Higgs boson of 112.0 GeV is set at the 95% confidence level. The most significant high mass candidate is a Hν¯ν event. It has a reconstructed Higgs mass of 115 GeV and it was recorded at √s = 206.4 GeV.Facultad de Ciencias Exacta