Cosmic ray astronomy aims to further the understanding of astrophysical phenomena to shed light on the structure and evolution of the Universe. The sources of the highest energy charged cosmic rays have not been clearly identified. Active Galactic Nuclei (AGN) and black holes distributed throughout the cosmos provide possible sources distributed through all epochs of expansion. Ultra High Energy Cosmic Rays (UHECRs) produce so-called cosmogenic neutrinos when they undergo inelastic collisions with the cosmic microwave background radiation. Over cosmic distances, neutrino mixing produces approximately equal populations of the three neutrino species when they get to the earth. Various astrophysical models for proton shock acceleration in the jets of AGN give a range of neutrino flux and energy distributions in the 0.1-1.0 EeV range.
Because the neutrino cross section rises with energy, neutrinos in this energy range are too energetic to penetrate the earth. This group proposes to construct a small prototype TAUWER array that will detect the decays of tau-leptons produced by tau-neutrinos moving upward along a chord in the earth's crust. The detector will sit on a steep mountain slope looking down along the chord near a zenith angle of 92 degrees. This proposal will initiate the TAUWER project, building 5 stations to study their performance in the field and to identify improvements and simplifications for the full system. Prototype detection elements have been tested and show clear discrimination capability between upward-coming and downward-moving particles. TAUWER is a modest cost, quickly deployable experiment that will provide new measurement capability and good overlap with other projects in this area. The successful completion of this one-year effort will establish the feasibility of installing and operating a complete TAUWER.
This proposal draws on the experience from a spring 2007 engineering course at CMU involving 10 undergraduate engineers and social science students. An expansion to include high school students and teachers is planned for the full project. Data from the full installation will be complementary to other neutrino astrophysics experiments.
