Enhancements to the Observatory: HEAT and AMIGA Peter O. Mazur Director’s Review December 15,

The Goals Extend the energy reach down to ~0.1 EeV – Main Observatory sensitive down to ~3 EeV – Transition from galactic to extragalactic origin expected to occur between 0.1 EeV and 10 EeV. – Overlap with highest energy LHC measurements for understanding of hadronic interactions Enhancement to FD to extend energy spectrum and composition measurements from 0.1 EeV to overlap with main Observatory energy range. Enhancement to SD to measure spectrum above ~0.3 EeV to overlap with main Observatory and to measure composition (using buried muon counters) from 0.3 – 3 EeV Both enhancements provide source angular position measurement for large scale anisotropy determination. 2

Fluorescence Detector Enhancement: HEAT: High Elevation Auger Telescopes Main telescopes consist of four sites with six telescopes each, with each telescope covering 30°×30° HEAT consists of one site (180m from Choihueco FD telescopes) with three telescopes. – Telescopes similar to main FD but they can be tilted upward by 30° – Operation at 0°: calibration and overlap with Coihueco telescopes. – Operation at 30°: sensitive to low energy showers which occur higher in the atmosphere and, being fainter, must be closer to the detector. 3

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HEAT and the Infill 5

Surface Detector Enhancement AMIGA: Auger Muon and Infill for the Ground Array Main array is 1600 surface detectors (SD) with 1.5 km spacing, sensitive down to ~3 EeV. Infill array of identical SD embedded in main array with spacing 750 m lowers sensitivity limit to ~0.3 EeV. Muon counters being installed paired with infill SDs. 6

Infill vs. Main Array Trigger Efficiency 7

Preliminary Energy Spectrum 8

Muon Counters 9

Enhancements Status HEAT complete and operating as expected AMIGA 750 m infill complete and operating as expected AMIGA Muon counters under development and in production Fermilab was not involved in HEAT Fermilab has minimal involvement in AMIGA – Fermilab made the scintillator, paid for by others. – Peter Mazur advised on design and production of muon counters. 10