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Claudio Di Giulio University of Roma Tor Vergata, INFN of Roma Tor Vergata

IDAPP 2D Meeting, Ferrara, May 3 2007. Claudio Di Giulio University of Roma Tor Vergata, INFN of Roma Tor Vergata. The origin and nature of cosmic rays above 10 19 eV is not understood…. 38° South, Argentina, Mendoza, Malargue 1.4 km altitude. The physics case.

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Claudio Di Giulio University of Roma Tor Vergata, INFN of Roma Tor Vergata

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  1. IDAPP 2D Meeting, Ferrara, May 3 2007 Claudio Di Giulio University of Roma Tor Vergata, INFN of Roma Tor Vergata The origin and nature of cosmic rays above 1019 eV is not understood… 38° South, Argentina, Mendoza, Malargue 1.4 km altitude

  2. The physics case • Evidence for Ultra High Energy Cosmic Rays > GZK cutoff ? • Near sources (<50 Mpc) ? • Production-acceleration mechanism? • Composition? • Challenging rate: ≈ 1 / Km2 / sr / century above 1020 eV! Auger aims to measure the properties of the highest energy cosmic rays with unprecedented precision.

  3. Status Southern Observatory Malargue, Argentina Surface Array 1600 detector stations 1.5 Km spacing 3000 Km2 Fluorescence Detectors 4 “Eye” 6 Telescopes per“Eye” 24 Telescopes total Last L.A. pmt!! (Malrgue Oct.2006) CLF ~ 1300 SD tanks, AllFD data taking.

  4. 300-400 nm light from de-excitation of atmospheric nitrogen (fluorescence light) ≈ 4 γ’s / m /electron 1019 eV 1010 e Cross-calibration, improved resolution, control of systematic errors The Auger hybrid detector concept • Fluorescence Detector • E + longitudinal development • Time ≈ direction • ≈ 10% duty cycle • Surface Detector • Shower size ≈ E • Time ≈ direction • 100% duty cycle

  5. GPS antenna Communications antenna Solar panels Lateral Distribution Function Battery box Electronics enclosure Tank signal S1000 Plastic tank with 12 tons of water 3 – nine inch photomultiplier tubes The Surface Detectors Shower energy ~ S1000

  6. FADC trace 100 s The Fluorescence Detector UV filter window PMT camera Corrector ring Spherical surface camera 440 PMT with light collectors Large 300x300 field of view 1.5º pixel fov 3.4 m spherical mirror

  7. FD calorimetry Nγ≈ Edep Nγ(λ) T(λ) A Ri ε(λ) Np.e.= ∑ Nγ(λ) A’ ε(λ) T (λ) λ Ri2 Fluorescence Geometry Detector Atmosphere yield • Air as an electromagnetic-hadronic calorimeter medium: 25 radiation lengths, 15 interaction lengths • UHE cosmic ray high energy secondary hadrons interaction vs decay very good hadronic calorimeter “e/h” → 1 (only 10% of energy not in e.m. cascade) • Robust energy determination for UHECR, small syst. FD Systematic uncertainties Tot. ΔE/E ~25% ~10% ~10% ~15% 40

  8. Alternative Profile Rec. Method: the “spot method” Claudio Di Giulio – Rome Tor Vergata University • Based on a detailed description of the light distribution on the camera surface Spot coming from spherical aberration Inclusion of the shower lateral size (D.Gora et al., astro-ph/0505371) fPMT(1) fPMT(2) ➾ Prediction of the expected ADC traces from the hypotized long. profile ➾ Cherenkov contribution from the hypotized profile: NO iteration ➾ Description of the signal on the camera borders and accounts for camera inhomogeneities (Mercedes) GAP-Note 2006-026

  9. SD Energy calibration with hybrid events ICRC 2005 ICRC 2007 • S38 and EFD uncertainties assigned on event by event basis. • (my contribute in the Auger Energy Spectrum Working Group) Simultaneous observation by Fluorescence and Surface Detectors: only ≈10% of events but extraordinary impact on the quality of our physics results! ESD = A (S38)b b ~ 1 The power of hybrid…..We DO NOT depend on shower simulation! Calibration uncertainty improves with hybrid statistics.

  10. FD “Test Beam” Central Laser Facility 355 nm laser SD tank 26 km Optic fiber

  11. CROSS CHECK OF DRUM CALIB. • Beam of up to 8 mJ 355 nm photons • Rayleigh scattered to the FD • Energy probe measurement of the beam with 10% uncertainty CLF (355 nm) 30 Km  difficult Roving (337 nm) 3 Km  safer Drum (375 nm) May 2005 (Roving+CLF) August 2006 (Roving) Confirmed FD photometric calibration at the level 10% Analysis complicated by variable and poor atmospheric conditions GAP-Note 2006-095 ICRC 2005 p.335-338

  12. My contributes: • Study of “stereo” FD events (geometry and profile reconstruction) [1]. • Study of CLF laser shots with FD [2] and cross-check of the FD optical calibration[4]. • Study and implementation of new method for the shower profile reconstruction of the FD events [3]. • Collaboration in the AIRFLY experiment.[5] • SD Calibration for ICRC 2007 Auger Energy Spectrum (under studying ). [1] Eventi Stereo dell’Osservatorio Auger, Physics Degree Thesis Università degli Studi di Roma Tor Vergata. ROM2 F/2005/17 [2] ICRC 2005 (108): The central laser facility at the Pierre Auger Observatory. [3]GAP-Note 2006-026: A New Methods for the Longitudinal Profile Reconstruction of the Auger Fluorescence Detector Events. [4]GAP-Note 2006-026: Cross-check of the Fluorescence Detector optical calibration with laser shots. [5]Astroparticle Physics: In press Accepted Manuscript Measurement of the pressure dependence of air fluorescence emission induced by electrons.

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