Transcript Slide 1
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!):
Φ ≈ 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
Spain
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 -> 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 nu’s w/cosmic background neutrinos (-> 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 &
Kuz’min
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 > 100 events/yr above 1020 eV
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View of Los Leones
Fluorescence Site
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PMT camera
3.4 m spherical mirror
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)
FADC
trace
100 s
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Energy reconstructed from measured maximum size --13
calorimetric (minimal MC)
Reconstructed longitudinal profiles
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μ
e
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θ~ 48º, ~ 70 EeV (7 x 1019 eV)
Lateral density
distribution
km
18 detectors triggered
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(particles per square meter)
“Deep” shower
“High” shower
R ≈ 1000m
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SD Energy Calibration
The power of hybrid…..
Does NOT rely on shower simulation
SD Energy resolution
better than 20%
SD
ESD = A (S38)b
b~1
FD
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Includes hybrid data (See Settimo & Auger Collab, EPJ (2012))
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“Infill”
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Here: from 2011
ICRC
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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
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Nuclear Composition: Shower Depths of Maximum Xmax
Anisotropy
Anisotr
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
“Tail” dominated
by protons
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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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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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спасибо
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