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Jim Matthews Louisiana State University

Results from the Pierre Auger Observatory. Jim Matthews Louisiana State University. Up to the “knee” – observe nuclei from H to Fe and beyond. ~ E -2.7. Very low flux … Very big detectors. ~ E -3.1. Above 10 20 eV ( 50 Joules !): Φ ≈ 1 per km 2 per century.

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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

  2. Up to the “knee” – observe nuclei from H to Fe and beyond ~ E-2.7 Very low flux … Very big detectors ~ E-3.1 Above 1020 eV (50 Joules!): Φ ≈ 1 per km2 per century

  3. Units:1018 eV = 1 EeV , 1021 eV = 1 ZeV = 160 Joules ! 1 Tyson ? 1 Clemens ? 1 Harry? 1 Curly?

  4. Argentina Australia Bolivia* Brasil Croatia Czech Republic France Germany Italy Poland Mexico Netherlands Portugal Romania* Slovenia Spain United Kingdom USA Vietnam* ~ 500 Scientists 19 Countries

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

  6. Protons are trapped in our Galaxy up to ~1018eV • Protons can travel straight lines above ~1020eV • Charged-Particle Astronomy E=1018eV Trajectories of Cosmic Ray Protons in the Galaxy E=1019eV E=1020eV

  7. 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: photons, neutrinos

  8. PLASMA SHOCK WAVE Fermi Acceleration repeated encounters with the shock front N(≥E) ~ E-γ γ ≈ P/α ≈ 2.0 per collision: P = prob of escape α = ∆E/E PARTICLE

  9. HESS - smoking guns in TeV ’s ? RX J1713 - 20  Gamma-rays X-rays Chandra Hinton, WatsonFest, Leeds

  10. Something much bigger than an SNR, lasts a lot longer … higher E

  11. Acceleration can occur both at remote termination shocks and at shocks near the central engine AGN VLA image of Cygnus A An active galaxy M. Urry, astro-ph/0312545

  12. B Emax = β B L Ze βcshock speed Zeparticle charge L

  13. “GZK” First pointed out in 1966 in two papers, one by Greisen and one by Zatsepin & Kuz’min • p + (2.7oK)  p 0 • n + Nuclei photo-disintegrate at similar thresholds, distances

  14. (cosmic ray proton) Extensive Air Showers (1019eV) N ~1010 particles 90% e+/-10% μ +/-(primary proton) e+/- ~ 5 MeVμ +/- ~ 5 GeV

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

  16. 38° South, Argentina, Mendoza, Malargue

  17. Surface Array 1650 detector stations 1.5 Km spacing 3000 km2 Fluorescence Detectors 4 Telescope enclosures 6 Telescopes per enclosure 24 Telescopes total

  18. View of Los Leones Fluorescence Site

  19. 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

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

  21. Reconstructed longitudinal profiles

  22. telescope calibration includes the atmosphere Mike Sutherland

  23. μ e

  24. Erice – July 2010

  25. Fluctuations A shower at a given energywill be larger on the ground if it starts deeper

  26. (particles per square meter) “Deep” shower “High” shower R ≈ 1000m

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

  28. SD Energy Calibration The power of hybrid…..Does NOT rely on shower simulation SD SD Energy resolution better than 20% S (1000 m) ESD = A (S38)b b ~ 1 FD

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

  30. Improved!

  31. GZK E -γ p log (flux) E ~ 5x1019eV log E

  32. Or: Source? E -γ p log (flux) Fe Z = 26 Emax 26xEmax log E

  33. E air p E , A air Inferring the Primary Mass Geometric cross section: λp = 4 λFe log Nint Fe λp ≈ 40 g/cm2 λFe ≈ 10 g/cm2 P X1

  34. 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

  35. UHECR Composition E air p Xmax~ ln(E) E , A air Xmax~ ln(E/A) E ~ 1019 eV Both the mean and the RMS of Xmaxare sensitive to composition

  36. (Only about 10% of all events can have Xmax measured directly) 2013 update of Physical Review Letters 104 (2010) 091101

  37. T. Pierog, ECRS 2012

  38. Ratioof observed muonsto proton simulations Data show more muonsthan simulations L. Nellen, European CR Conf., Moscow, 2012

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

  40. Phys. Rev. Lett. 109 (2012) 062002

  41. Photon limits • p + (2.7oK)  p 0 • n +

  42. p + (2.7oK)  p 0 • n +

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