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Status of the Pierre Auger Observatory

Status of the Pierre Auger Observatory. Aaron S. Chou Fermilab Fermilab Users’ Meeting June 3, 2003. Auger: a new observatory to study the highest energy phenomena in the universe (10 18 eV and up).

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Status of the Pierre Auger Observatory

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  1. Status of the Pierre Auger Observatory Aaron S. Chou Fermilab Fermilab Users’ Meeting June 3, 2003

  2. Auger: a new observatory to study the highest energy phenomena in the universe (1018 eV and up) • How can particles be accelerated to such extreme energies? Or do they come from the decay of some more massive cosmological object? • What are they? Protons? Ions? Gammas? Neutrinos? Exotics? • What/where are their sources? • Above 1019 eV cosmic rays point back to their sources • Charged particle astronomy! • How can they even reach us? • Protons cool in the CMB above the photo-pion production threshold (a few 1019 eV) • GZK feature or not? The Cosmic Ray Spectrum (S. Swordy) New vocab: GeV, TeV, PeV, EeV, ZeV…

  3. The HiRes (Fluorescence) /AGASA (Surface Detector) Controversy • Spectrum multiplied by E3 to remove power law. • Discrepancy could be a 30% energy systematic. • Auger will cross-calibrate using both methods of energy determination on the same showers in the same atmosphere: • Sampling of the ground particles • Nitrogen fluorescence calorimetry HiRes, ICRC 2001

  4. What are the properties of the Auger super-beam? • CM energy = 200 TeV (for 1019 eV protons) • Transverse emittance = c/H0 * 2 * pi (is it really isotropic?) • Luminosity = 40 / kb / s (but no down time!) • 1 evt/km2/year * 3000 km2 • diffractive pp cross-section = 250 mb • Not much hope for high-Pt hadron physics… (But look out for neutrinos with very small SM cross-sections!)

  5. The Auger Calorimeter • We do not get much funding, but luckily nature has provided us with a very large calorimeter suitable for use with our low luminosity beam! Neutrino converter: Relic massive neutrino halo  Excite Z0 resonance at1021 eV • Hadronic/EM calorimeter: • 7 km of air = 1000 g/cm2 • hadronic mean free path = 84 g/cm2 • Hundreds of billions particles/shower  • Continuous sampling of N2 fluorescence up to 30 km @ 1019 eV. • Sampling of shower particles at ground. Neutrino target: Earth: neutrino mean free path < 300 km @ 1018 eV

  6. Detection of neutrinos via horizontal air showers. • Large zenith angle hadronic showers have lost most of their EM component by the time they reach the detector. Only the hard muons are left. • Neutrinos can shower deep in the atmosphere, right over the detector  Easy to identify • Tau neutrinos can also interact in the earth, and the escaping Tau particle can decay and form an upward-going shower. SM Interaction Prob 10-4 Auger event rate = few/year. Good chance to check for enhanced interaction rate (10-100x) at TeV scale.  Large extra dimensions, etc. (Feng and Shapere, hep-ph/0109106) Our neutrino sensitivity is comparable to IceCube! ( at > 0.1 EeV)

  7. The Surface Detector (SD) Array • 1600 water Cherenkov detectors (R=1.5 km) • Solar powered. DAQ via radio • Get shower direction from timing • High statistics, 100% duty cycle • Get energy from fit to MC lateral distribution function (signal versus transverse distance) • Atmospheric muons  standard candle for an end-to-end calibration of the detector response • Can measure signal strength in units of Vertical Equivalent Muons (VEM) Single vertical muon peak defines the VEM unit Number of evts Integrated signal (arbitrary units)

  8. The Fluorescence Detector (FD) • Measure N2 fluorescence from the EM portion of the shower which carries 90% of the shower energy • Convert to energy measurement using fluorescence yield measurements from lab experiments (ongoing) • Correct for muons, neutrinos, and the portion of shower hitting the ground… (Gaisser-Hillas profile) • Get geometry from pixel pattern, timing. A Shower profile (Auger data) # particles / 109 24 telescopes in 4 buildings Atmospheric depth

  9. The Engineering Array (EA) • An engineering array of 32 surface detectors (SD) has been operational and taking data for more than a year. • In addition, we have 4 months of data from 2 fluorescence detectors (FD) installed in a building at the Southern edge of the array.  70 hybrid events with both SD and FD data

  10. An 11-tank data event—2 kinds of triggers • Threshold : single FADC bin above some threshold value for all PMTS. • Detects large signals from shower core.. 45 34 • 2) Time over Threshold : multiple consecutive bins above some lower threshold • Detects EM portion of shower extended in time from scattering.

  11. Carmen and Miranda • Two tanks separated by 11 meters. • Get the true error of the signal strength • Poisson statistics • Fluctuations in the lateral distribution of the shower particles • Measured GPS time error = 8 ns  1 degree angular resolution @1019 eV) From tank sep. Time Diff (ns)

  12. Engineering Array Events Beginning of the Auger charged-particle astronomy program!

  13. A Hybrid Event Image on FD camera (1.5 degree pixels) EA tanks Y (km) Time (ns) X (km) Angle in shower-detector plane

  14. The Auger Production Phase • Surface Detector: • Currently, 70 pre-production tanks are installed and now being instrumented • By the end of 2003 -- 350 operational detectors • The largest array in the world! • Full array deployed in 2005. • Fluorescence Detector: • By the end of 2003 -- 12 telescopes operational • All 24 telescopes by 2005. By early next year, we will have ¼ of the Auger array fully operational and taking physics data!

  15. By the end of this summer….

  16. Summary • Auger is well underway with an Engineering Array operational for over a year. • We have developed new hardware, triggers, calibration schemes and physics analysis techniques • Even with only 32 tanks, we already have candidates for large air showers • New production detectors are currently being installed • 350 SD, 12 FD telescopes by the end of the year • Look for physics results as early as next summer.

  17. NRC: Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century • What is dark matter? • What is the nature of the dark energy? • How did the universe begin? • Did Einstein have the last word on gravity? • What are the masses of the neutrinos and how have they shaped the evolution of the universe? • How do cosmic accelerators work and what are they accelerating? • Determine the origin of the highest-energy gamma rays, neutrinos, and cosmic rays. The committee supports the broad approach already in place and recommends that the United States ensure the timely completion and operation of the Southern Auger array. …

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