Paul Sommers
Fermilab PAC
Nov 12, 2009
Auger Science
South and North
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Results from Auger South have already settled some fundamental issues and made clear what is now needed
•To identify the sources of UHE cosmic rays
•To uncover the acceleration process
•To establish the particle types
•To test hadronic interaction properties at extreme energies
The key is a systematic study of the trans-GZK particles
Auger North targets this high energy frontier by increasing the aperture of the Auger Observatory by a factor of eight at trans-GZK energies
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Exposure (Auger South, so
far)
Now nearly ten times the AGASA exposure.
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HiRes @ 10 EeV
HiRes @ 100 EeV
2 years of full aperture
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Science Results
• Spectrum with clear ankle and “GZK” suppression
• Anisotropy of arrival directions above 55 EeV
• Limit on photon flux at 10 EeV using surface detector
• Limit on photon flux at 3 EeV using fluorescence detector
• Limit on Earth-skimming tau neutrinos
• New limit on all flavors of neutrinos using near-horizontal showers
• Statistical analysis of Xmax values for energies up to 30 EeV
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The Auger Observatory in the Southern Hemisphere Now fully deployed in Argentina
1600 water Cherenkov stations
24 fluorescence telescopes (30˚x30˚)
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60 km
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The Auger Energy SpectrumReady for publication this month (PLB)
SD + FD
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Five-parameter fit: index, breakpoint, index, critical energy, normalization
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The Auger Energy SpectrumReady for publication this month (PLB)
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Comparison with models
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Anisotropy
The Auger Energy SpectrumReady for publication this month (PLB)
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The Auger Sky above 55 EeV
27 events as of November 2007
Science 318 (2007), 939
Astroparticle Physics 29 (2008), 188
58 events now (with Swift-BAT AGN density map)
Simulated data sets based on isotropy (I) and
Swift-BAT model (II) compared to data (black
line/point).
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Log(Likelihood)
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Shower Depths of Maximum Xmax
Ready for publication this month (PRL)
These suggest high cross section and high multiplicity at high energy.
Heavy nuclei?
Or protons interacting differently than expected?
Information lacking for the (anisotropic) trans-GZK energy regime!
(Crucial for calculation of the diffuse cosmogenic neutrino flux)
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Anisotropy Anisotropy
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Trans-GZK composition is simpler
Light and intermediate nuclei photodisintegrate rapidly.
Only protons and/or heavy nuclei survive more than 20 Mpc distances.
Cosmic magnetic fields should make highly charged nuclei almost isotropic.
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•Far greater exposure is needed to
• Identify the class of sources via anisotropy
• Measure the spectra of bright sources or source regions
• Determine the particle type(s) above 55 EeV
• If protons, measure interaction properties above 250 TeV (CM)
• Determine the diffuse cosmogenic intensity of neutrinos and photons
• Detect cosmogenic neutrinos and photons
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Auger North is designed to have seven times the aperture for trans-GZK cosmic rays. Auger South and North together will have eight times the collecting power of the present Observatory.
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The Ascent of Exposure
Logarithmic Scale Linear ScaleLinsleys x105 Linsleys
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TA
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Auger exposure to tau Neutrinos
Neutrinos can be identified as “young” showers at very great atmospheric slant
depth (either upward or downward).
The Auger UHE Neutrino Observatory
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Limit on Tau Neutrinos
Physical Review Letters 100 (2008), 211101
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Depends on source spectral index, Emax, and evolution; also on the particle types!
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The UHE Gamma Ray Astronomical Window
Photon showers penetrate deeper than hadronic showers.
They can be recognized individually with hybrid measurements.
A photon component can be measured statistically by the surface array.
Photon attenuation length exceeds 10 Mpc for E > 2 EeV
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UHE Photon Limits(strongly constrain top-down scenarios)
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Astroparticle Physics 31 (2009), 399
Astroparticle Physics 29 (2008), 243
Astroparticle Physics 27 (2007), 155
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Enhancements at Auger South
HEAT: High Elevation Auger Telescopes
AMIGA: Auger Muon and Infill Ground Array
,
AERA: Auger Engineering Radio Array
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Summary
Deployment is complete for the Auger Observatory in Argentina
Important science results:
There IS a suppression of the energy spectrumTrans-GZK arrival directions correlate with local structureEnergy loss (e.g. GZK) is confirmed above 55 EeV (The spectral steepening is not just due to sources “running out of steam”)There ARE detectable UHE sources within the GZK sphereIntriguing trend in Xmax distributions for energies up to 30 EeVNew Auger limits on diffuse neutrinosNew Auger limits on diffuse photons (ruling out generic top-down models)
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Auger North
Auger North targets the key energy regime above 55 EeVExploit the anisotropy (200 events/year instead of just
25/year)Exploit the simplified composition (only protons and/or
heavy nuclei)
Goals:Identify the astrophysical class of sourcesStudy the spectra of the brightest sources or regions
individuallyStudy cosmic magnetic fields by spectrometryConstrain hadronic interactions at CM energy > 250 TeV
Complementary approach to cosmogenic (GZK) neutrinos and photons: Determine the diffuse fluxes by measuring the trans-GZK cosmic
ray spectrum and composition, and identifying the type of
astrophysical sources (their evolution) Detect the cosmogenic neutrino and photon fluxes directly(This can test theories for modified neutrino interaction cross sections)
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