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Jim Matthews Louisiana State University

Results from the Pierre Auger Observatory. Jim Matthews Louisiana State University. ECRS, Moscow , 4 July 2012. Very low flux … Very big detectors. ~ E -2.7. ~ E -3.1. Above 10 20 eV ( 50 Joules !): Φ ≈ 1 per km 2 per century. Argentina Australia Bolivia * Brasil Croatia

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Jim Matthews Louisiana State University

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  1. Results from the Pierre Auger Observatory Jim Matthews Louisiana State University ECRS, Moscow, 4 July 2012

  2. Very low flux … Very big detectors ~ E-2.7 ~ E-3.1 Above 1020 eV (50 Joules!): Φ ≈ 1 per km2 per century

  3. Argentina Australia Bolivia* Brasil Croatia Czech Republic France Germany Holland Italy Poland Mexico Netherlands Portugal Romania Slovenia Spain United Kingdom USA Vietnam* ~ 500 Scientists 17 Countries

  4. Aims of the experiment • Measure the energy spectrum of high energy cosmic rays up to and beyond energies of 1020 eV • Determine the sources of these cosmic rays • Determine the elemental composition of cosmic rays • Study extensive air showers -> particle interactions

  5. How to get particles to extreme energy • Fermi Acceleration (Bottom-Up) - repeated encounters with strong plasma shocks - naturally produces power-law with correct index - maximum energy can be extremely large - observed in nature • “Exotic” (Top-Down) - decay of massive relic particles - interaction of nu’s w/cosmic background neutrinos (-> Z) - topological defects, other things ? - Signature: protons, photons, neutrinos

  6. “GZK” First pointed out in 1966 in two papers, one by Greisen and one by Zatsepin & Kuz’min p + (2.7oK)  p +  Nuclei photo-disintegrate at similar thresholds, distances

  7. Surface Arrays and Fluorescence Detection - Arrays: 24/7 operation, very large size (statistics) - Fluorescence: ‘calorimetry’ = good energy resolution (spectrum)

  8. 38° South, Argentina, Mendoza, Malargue

  9. Surface Array 1650 detector stations 1.5 Km spacing 3000 km2 Fluorescence Detectors 4 Telescope enclosures 6 Telescopes per enclosure 24 Telescopes total Design: AGASA spectrum > 100 events/yr above 1020 eV

  10. View of Los Leones Fluorescence Site

  11. The Fluorescence Detector FADC trace 100 s Spherical surface camera 440 PMT with light collectors Large 300x300 field of view 1.5º pixel fov (spot 1/3 of pixel) PMT camera 3.4 m spherical mirror

  12. Energy reconstructed from measured maximum size --- calorimetric (minimal MC)

  13. Reconstructed longitudinal profiles

  14. μ e

  15. Lateral density distribution θ~ 48º, ~ 70 EeV (7 x 1019 eV) km 18 detectors triggered

  16. SD Energy Calibration The power of hybrid…..Does NOT rely on shower simulation SD SD Energy resolution better than 20% ESD = A (S38)b b ~ 1 FD

  17. Includes hybrid data (See Settimo & Auger Collab, EPJ (2012))

  18. “Infill”

  19. Here: from 2011 ICRC

  20. Inferring the Primary Mass Variation of Depth of Shower Maximum with Energy p Xmax ************************ Fe Xmax correlates tightly with the depth of 1st interaction log E

  21. Nuclear Composition: Shower Depths of Maximum Xmax Anisotropy Anisotropy These suggest high cross section and high multiplicity at high energy. Heavy nuclei? Or protons interacting differently than expected? (See Nellen presentation, this meeting) Statistics lacking for the (anisotropic) trans-GZK energy regime! (Crucial for calculation of the diffuse cosmogenic neutrino flux) Physical Review Letters 104 (2010) 091101

  22. SD: Development of Muons in Shower SD: Asymmetry of Shower front thickness FD: Mean depth of Shower Max FD: Fluctuations of Shower Max Spectral “Ankle”

  23. Presentation by Nellen: Data show more muons than simulations

  24. Proton-Air Cross Section from the Depth of Shower Maximum “Tail” dominated by protons

  25. To appear in Phys. Rev. Lett. 2012

  26. To appear in Phys. Rev. Lett. 2012

  27. Photon limits See presentation of Navarro at this meeting …

  28. See presentation of Navarro at this meeting …

  29. Summary • Energy spectrum exhibits ankle and GZKsuppression • The sources are extragalactic, within the “GZK sphere”: (weak) anisotropy persists above ~60 EeV • The composition is baryonic, appearing to become iron-dominated (or new particle physics … models do not give enough muons) • p-Air, p-p cross sections beyond the LHC energy • Few/no photons or neutrinos (disfavors exotic “top down” models) • Photons/neutrinos nearing GZK regime

  30. What’s Next? Auger has been “operating” since 2004, fully deployed since 2008. The international agreement runs for 3.5 more years (end of 2015) We hope to continue after that, are exploring new technologies in use now or can be started very soon … -- Auger Engineering Radio Array - AERA - see presentation by Fraenkel -- Microwave, GHz, ... prototypes operating -- Focus on better composition determination through new muon detectors, new flourescence techniques, … R&D спасибо

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