• Energy Research

This paper summarizes some highlights from the Pierre Auger Observatory that were presented at the ICRC 2011 in Beijing. The cumulative exposure has grown by more than 60% since the previous ICRC to above 21000 km^2 sr yr. Besides giving important updates on the energy spectrum, mass composition, arrival directions, and photon- and neutrino upper limits, we present first measurements of the energy spectrum down to 3 x 10^{17} eV, first distributions of the shower maximum, X_max, together with new surface detector related observables sensitive to X_max, and we present first measurements of the p-air cross section at ~ 10^{18} eV. Serendipity observations such as of atmospheric phenomena showing time evolutions of elves extend the breadth of the astrophysics research program. Proceedings of Highlight talk presented at ICRC 2011, Beijing. 10 pages, 13 figures

Abstract The Michel parameters ϱ, η, ξ, and ξδ, the chirality parameter ξ h and the τ polarization P τ are measured using 32012 τ pair decays. Their values are extracted from the energy spectra of leptons and hadrons in τ − → l − ν l ν τ and τ − → π − ν τ decays, the energy and decay angular distributions in τ − → ϱ − ν τ decays, and the correlations in the energy spectra and angular distributions of the decay products. Assuming universality in leptonic and semileptonic τ decays, the results are ϱ = 0.794±0.039±0.031, η = 0.25±0.17±0.11, ξ = 0.94±0.21±0.07, ξδ = 0.81±0.14±0.06, ξ h = −0.970±0.053±0.011, and P τ = −0.154±0.018±0.012. The measurement is in agreement with the V-A hypothesis for the weak charged current.

A search for exotic unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed with the L3 detector at LEP. Sequential, vector and mirror natures of heavy leptons are considered. No evidence for their existence is found and lower limits on their masses are set.