This award supports the high-energy gamma-ray group at the University of Wisconsin-Madison in their participation in the High-Altitude Water Cherenkov (HAWC) experiment. HAWC is a large field-of-view Teraelectronvolt (TeV) gamma-ray detector currently under construction near Pico de Orizaba in Mexico. HAWC will map TeV gamma-ray sources with daily coverage of half the sky. The observation of Galactic and extragalactic TeV gamma-ray sources with HAWC and the measurement of their energy spectra will greatly enhance our understanding of the origin of cosmic rays. HAWC will also map the arrival direction distribution of TeV cosmic rays with unprecedented sensitivity and help us understand the large- and small-scale structure observed in cosmic-ray sky maps. The observation of distant blazars will constrain the extragalactic background light and the intergalactic magnetic field, which may have been formed during primordial phase transitions in the early Universe.
The group at UW-Madison is participating in the development of the trigger and readout electronics, the data acquisition, and the development of the analysis software. The HAWC electronics integration site is located at UW- Madison, and new electronics are integrated into the system and tested there before being shipped and installed at the site. The UW-Madison group is also engaged in data analysis. With early data from the 100-tank configuration, the group will begin a detailed study of the Crab Nebula and the shadow of the Moon to understand and fine-tune the detector performance. They will also study the large- and small-scale cosmic-ray anisotropy. The group will draw on its experience studying the cosmic-ray anisotropy in the southern sky with IceCube, and eventually combine the HAWC and IceCube data sets for a full-sky analysis.
Broader Impacts: The HAWC group at UW-Madison will continue to contribute to outreach activities that enhance the general public's appreciation and understanding of science. The group will also participate in local outreach programs like "Bringing the Universe to Wisconsin."
