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The Auger Project

The Auger Project. Seeking the Source of Ultra High Energy Cosmic Rays. A New Window on Astronomy. Generic Colloquium Slides Prepared December 11, 1997. David F. Nitz University of Michigan. Outline. Introduction Historical Perspective CR Spectrum Extensive Air Showers Array layout

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The Auger Project

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  1. The Auger Project Seeking the Source of Ultra High Energy Cosmic Rays A New Window on Astronomy Generic Colloquium Slides Prepared December 11, 1997 David F. Nitz University of Michigan

  2. Outline • Introduction • Historical Perspective • CR Spectrum • Extensive Air Showers • Array layout • EeV data • Possible Sources of Cosmic Rays • “Standard” Acceleration • Propagation and GZK • Top down (topological defects) • Monopoles • Gamma Ray Bursts • Observations and Physics Issues • Magnetic fields • Point Sources • AGASA pairs • Sky Coverage • Auger Detectors & Techniques • Fluorescence detectors • Tanks • Hybrid Operation • Timing • Trigger • Front-end electronics • Communications network • Energy, Direction, Composition resolution

  3. The Beginning Ever since Victor Hess discovered cosmic rays in 1912, a primary question has been "Where do they come from?". After more than 80 years of research this question remains largely unanswered. The origin of the highest energy cosmic rays remains one of the great unsolved mysteries of physics.

  4. The Observed Cosmic Ray Spectrum

  5. Layman’s Terms?

  6. Energy Scales

  7. The Highest Energy Particle Ever Observed E = 3 x 1020eV50 J!

  8. Flux of EeV Particles

  9. The Question

  10. The International Collaboration

  11. A 1019 eV Extensive Air Shower

  12. Auger Array Layout

  13. Two Hemispheres Anu Talvari is an artist of Estonian origin, born in Sweden and living in Buenos Aires -- a background not unlike the world-wide composition of the Auger Collaboration. She describes the painting thusly: “Earth. The Blue Planet. The known space is enclosed in the lower left corner. The unknown space opens in the upper right corner. Two Auger Observatories installed in both hemispheres. Two eyes looking for information from the unknown space.” The Auger Project is named after the late French physicist Pierre Auger, who discovered extensive air showers. He received a Nobel Prize for his work on “Auger electrons” and was influential in the founding of CERN.

  14. Auger Observatory Sites

  15. Northern Hemisphere Site

  16. Southern Hemisphere SiteArgentina

  17. Site Photos

  18. Astrophysical Miscellanea

  19. Possible Sources Astrophysical Acceleration Mechanisms • Diffusive shock acceleration (Fermi) in extended objects • Lobes of radio galaxies (Biermann) • Galaxy cluster accretion shocks (Kang, et. al) • Collisions of galaxies (Cesarsky) • Motion of galaxies in ISM • Acceleration in strong fields associated with accretion disks and compact rotating galaxies (Colgate)

  20. Black Hole(Artist’s Conception)

  21. NGC4151

  22. Caveats?

  23. Limits to Acceleration

  24. Attenuation of Cosmic Rays All known particles except neutrinos undergo interactions with the CMBR: This is the GZK cutoff

  25. Distance Scales

  26. The GZK Cutoff

  27. Possible Sources Exotic Mechanisms • Top down models • Decay of topological defects (Kibble, Bhattacharjee, Hill, ..) • Window to Post-Inflationary Reheating Epoch? (Kuzmin & Rubakov) • Decaying Vortons (Masperi & Solva) • Relic monopoles (Kephart & Weiler) (Escobar & Vazquez : “No”) • Acceleration in catastrophic events • In association with gamma ray bursts (Waxman, Vietri, Milgrom) • Other New Physics • Supersymmetric particles (Chung, Farrar, & Kolb) • Strongly interacting neutrinos (Bordes) • Needs to be at few Gev or cross section too low => not likely - ruled out by accelerator data (Halzen) • Decay of energetic new long lived progenator (Frampton, Keszthelyi, & Ng)

  28. Topological Defect Model CASA/MIA

  29. Auger Neutrino Detection Neutrino rates for 2 extreme extrapolations of the cross section (A recent analysis by Ralstan et al. suggests the cross section is likely to be closer to MRS)

  30. Magnetic Monopoles N.A. Porter, Nuov. Cim. 16 958 (1960) T.W. Kephart and T.J. Weiler, Astropart. Phys. 4, 271 (1996) • Consideration of relic monopoles motivated by 2 interesting facts: • Observed CR flux >1020 eV similar to Parker Bound • Higher flux would have violated bound • Lower flux would not have been observed • Dirac monopoles can be accelerated to >1020 eV with typical galactic magnetic field strengths and field coherence lengths • Must be relativistic to initiate observed air showers ==> masses <1019 eV • Observational consequences: • Energetic monopoles may be distributed preferentially in the direction of local galactic magnetic field • Air showers produced by monopoles may have distinctive characteristics • Detailed modeling of interactions of monopoles in upper atmosphere not yet been carried out. • Not known whether monopole can produce showers like those observed by AGASA and Fly’s Eye Auger is designed to be sensitive to air shower structure Phase transition correlation length Horizon size Monotonic relationship between monopole flux & mass (Parker bound) ==> (Doesn’t overclose Universe)

  31. Associationwith Gamma Ray Bursts E. Waxman, Phys. Rev. Lett. 75, 386 (1995) M. Vietri, Astrophys. J. 453, 883 (1995) E. Waxman, Astrophys. J. 444, L1 (1995) E. Waxman & P. Coppi, astro-ph/9603144 M. Milgrom & V. Usov, Astrophys. J. 448, L37 (1995) M. Vietri, Mon. Not. R. Astron. Soc. 278, L1 (1996) J. Miralda-Escude & E. Waxman, astro-ph/9601012 • If cosmological, power needed to account for flux of highest energy cosmic rays is comporable to average power in gamma rays • Observed spectrum consistent with Fermi acceleration in region and cosmological distribution • Observed rate • 2 CR events above 2 x 1020 eV observed in 26 months • ~1 GRB per 50 years within field of view of experiments and within 100 Mpc (GZK cutoff) ==> Requires 1020 eV protons produced in distant GRB burst are dispersed in time >50 years ==> Inter-Galactic Magnetic Field >10-12 G • Each of 2 highest energy CR within ~5o of a strong BATSE GRB (but not statistically compelling) • If highest energy CRs associated with distant GRBs • GZK cutoff • If GRB sources associated with luminous matter, expect CR anisotropy related to large scale structure of local (<100 Mpc) universe • Energy dependent delays in arrival times induced by IGMF • Brightest sources may be different at different energies • If highest energy CRs associated with local GRBs • No GZK cutoff • New >1020 eV events should be correlated with GRBs • Isotropic CR distribution due to observed isotropy of GRBs

  32. Possible Source Conclusions No really satisfactory model has emerged

  33. Magnetic Field Deflection

  34. AGASA pairs • 2-3 cases of 2 cosmic rays coming from the same direction within 1.6 deg. angular resolution • 1% random chance if isotropic distribution • 2% if use >4 x 1019 eV • One pair includes highest energy event observed by AGASA • Assume same species & source • Trace back 30-50 Mpc to source (Parker) Need more data, more sky coverage We expect >50 events in Auger from this source in same length of time (5 years)

  35. Auger Philosophy • Large aperture (>10X previous generation) • Uniform sky coverage • Hybrid operation • Good energy & direction measurement • Composition sensitivity

  36. Northern Observatory Exposure

  37. AGASA Events(E > 5x1019eV)

  38. Havarah Park Events (E > 5x1019eV)

  39. Southern Observatory Exposure

  40. Auger Observatory Exposure

  41. AGN Catalog of Huchra (< 100 Mpc) D ~ cz/H (for small z)

  42. Hybrid Operation

  43. Fluorescence Detector

  44. Surface Detector Station

  45. GPS Timing

  46. Tandar Test Tank White top: 55 ns Black top: 21 ns Data Simulation (Pryke)

  47. Trigger Hierarchy

  48. Auger Communications System Functional Overview Fluorescence Eye ~0.5 Mbits/s each Software Download ~2 Mbits/hr infrequently ~1.1Mbits/s aggregate 1600 stations Level 3 Trig. 0.2 hz Control Center Concentrator + ACK, NAK as required Remote Station 1600/site Level 2 Triggers ~20 Hz @24 bits each Poisson distributed Monitoring Data ~200 bits/s mean program controlled Event Data ~15 Kbits/s @ ~2600 interval Poisson distributed Control 100 bits/s?

  49. Test Tank at AGASA 1020 eV event 1.7 km from core 30o zenith angle

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