Jim Matthews

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Results from the Pierre Auger Observatory
Jim Matthews Louisiana State University
ECRS, Moscow, 4 July 2012
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Very low flux Very big detectors
E-2.7
E-3.1
Above 1020 eV (50 Joules!) F 1 per km2 per
century
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Argentina Australia Bolivia Brasil Croatia Czech
Republic France Germany Holland Italy Poland
Mexico Netherlands Portugal Romania Slovenia Spai
n United Kingdom USA Vietnam
500 Scientists 20 Countries
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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 -gt particle
  interactions

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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 nus w/cosmic background
  neutrinos (-gt Z)
• - topological defects, other things ?
• - Signature protons, photons, neutrinos

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GZK First pointed out in 1966 in two papers,
one by Greisen and one by Zatsepin Kuzmin
p ? (2.7oK) ? ? ? p ?
Nuclei photo-disintegrate at similar thresholds,
distances
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Surface Arrays and Fluorescence Detection -
Arrays 24/7 operation, very large size
(statistics) - Fluorescence calorimetry
good energy resolution (spectrum)
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38 South, Argentina, Mendoza, Malargue
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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 gt 100 events/yr above
1020 eV
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View of Los Leones Fluorescence Site
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The Fluorescence Detector
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
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Energy reconstructed from measured maximum size
--- calorimetric (minimal MC)
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Reconstructed longitudinal profiles
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? 48º, 70 EeV (7 x 1019 eV)
km
18 detectors triggered
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R 1000m
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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
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Includes hybrid data (See Settimo Auger Collab,
EPJ (2012))
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Here from 2011 ICRC
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Inferring the Primary Mass
Xmax correlates tightly with the depth of 1st
interaction
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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
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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
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Presentation by Nellen Data show more muons
than simulations
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Proton-Air Cross Section from the Depth of Shower
Maximum
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To appear in Phys. Rev. Lett. 2012
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To appear in Phys. Rev. Lett. 2012
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Photon limits
See presentation of Navarro at this meeting
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See presentation of Navarro at this meeting
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• Summary
• Energy spectrum exhibits ankle and GZK
  suppression
• 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

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Whats 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, RD
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