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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