1. Absolute Measurement of Air Fluorescence Yield for Ultra-High Energy Cosmic Rays Paolo Privitera Carlos Hojvat Fermilab, June 27 2008 FD SD

2. Auger results Flux suppression Anisotropy < 75 Mpc Astrophysical interpretation GZK horizon

3. Auger Energy Calibration Lateral density distribution Fluorescence Detector Surface Detector The largest systematic uncertainty is the air fluorescence yield (15%) The Auger energy scale is based on the FD calorimetric energy. 10 km

4. The Auger hybrid detector concept 300-400 nm light from de- excitation of atmospheric nitrogen (fluorescence light) ≈ 4 γ’s / m /electron 10 19 eV 10 10 e Light attenuation in the atmosphere; showers develop in 15 km Fluorescence spectrum Dependence on pressure, temperature and humidity Absolute yield 20 FD SD

5. AIRFLY measurements 391.4 nm 337.1 nm 353.7 nm relative band intensities Temperature and humidity dependence Pressure dependence

6. Chemistry Division Van de Graaf (0.6-3 MeV) Advanced Photon Source (6-30 KeV) HEP Division Advanced Wakefield Accelerator (3 MeV-15 MeV) AIRFLY beams Beam Test Facility at DA  NE INFN FRASCATI (50-750 MeV) ARGONNE ANL Collaboration: Cezch Republic, Germany, Italy, US

7. Chamber Gas system Vacuum pump Lead shielding support BTF (Frascati) Argonne Chemistry VdG

8. Absolute Fluorescence Yield at the Fermilab Meson Test Beam Goal: ≤ 5% uncertainty with the fluorescence/Cherenkov ratio method Photon Detector Particle beam Fluorescence photons Cherenkov photons Photon Detector Particle beam 45° mirror (a)(b) 337 nm filter Q.E uncertainty >10% Normalize to known yield: Q.E cancels Tested at Frascati and Argonne

9. Absolute Fluorescence Yield at the Fermilab Meson Test Beam Fluorescence/Cherenkov ratio method + independent laser calibration Low intensity: Integrating sphere, Ultra Bialkali PMTs (43% QE) Particle beam Photon Detector Integrating sphere Diffuser to be placed for Cherenkov run Cherenkov dump Acceptance counter Veto counter High energy (reduce multiple scattering, air as Cherenkov Radiatior) Well defined beam: single particle trigger and geometry Wide range of particles type and intensity

10. Collaborative Initiative Grant Crucial measurement for Auger (South and North); will have a strong impact in the Auger scientific results and in the UHECR field Use of Fermilab facility: Meson Test Beam University of Chicago and Fermilab have a long history of collaboration in Auger; Auger design Workshop held at Fermilab in 1995 Collaboration well matched for the success of the initiative P. Privitera (Chicago), C. Hojvat (Fermilab), H. Spinka (Argonne), AIRFLY collaborators Some hardware from AIRFLY Funds: 1 postdoc (100% FTE), hardware for new chamber 2 years proposal Tank n. 1600

11. Air fluorescence spectrum Argonne 3 MeV electron VdG, DC beam, 10 μA Spectrograph instead of monochromator: Insensitive to changes of beam intensity or position VdG Beam Spherical mirror Optical fiber L.O.T. Oriel MS257  = 0.1 nm Andor CCD DV 420

12. Chamber Gas system Vacuum pump Lead shielding support BTF (Frascati) HPD