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Paul Sommers Fermilab PAC Nov 12, 2009

Auger Science South and North. Paul Sommers Fermilab PAC Nov 12, 2009. 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

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Paul Sommers Fermilab PAC Nov 12, 2009

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  1. Auger Science South and North Paul Sommers Fermilab PAC Nov 12, 2009

  2. 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 Sommers FNAL 2

  3. Exposure (Auger South, so far) 2 years of full aperture HiRes @ 100 EeV HiRes @ 10 EeV Now nearly ten times the AGASA exposure. Sommers FNAL 3

  4. 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 Sommers FNAL 4

  5. The Auger Observatory in the Southern Hemisphere Now fully deployed in Argentina 1600 water Cherenkov stations 24 fluorescence telescopes (30˚x30˚) 60 km Sommers FNAL 5

  6. The Auger Energy Spectrum Ready for publication this month (PLB) SD + FD Sommers FNAL 6

  7. The Auger Energy Spectrum Ready for publication this month (PLB) Five-parameter fit: index, breakpoint, index, critical energy, normalization Sommers FNAL 7

  8. The Auger Energy Spectrum Ready for publication this month (PLB) Anisotropy Comparison with models 8 Sommers Lodz

  9. The Auger Sky above 55 EeV 58 events now (with Swift-BAT AGN density map) 27 events as of November 2007 Science 318 (2007), 939 Astroparticle Physics 29 (2008), 188 Simulated data sets based on isotropy (I) and Swift-BAT model (II) compared to data (black line/point). Log(Likelihood) Sommers FNAL 9

  10. Shower Depths of Maximum Xmax Ready for publication this month (PRL) Anisotropy Anisotropy 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) Sommers Lodz 10

  11. 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. Sommers Lodz 11

  12. 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 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. Sommers Lodz 12

  13. The Ascent of Exposure Logarithmic Scale Linear Scale Linsleys x105 Linsleys TA Sommers Lodz 13

  14. The Auger UHE Neutrino Observatory Neutrinos can be identified as “young” showers at very great atmospheric slant depth (either upward or downward). Auger exposure to tau Neutrinos 14 Sommers FNAL 14

  15. Limit on Tau Neutrinos Depends on source spectral index, Emax, and evolution; also on the particle types! Physical Review Letters  100 (2008),211101 Sommers Lodz 15

  16. The UHE Gamma Ray Astronomical Window Photon attenuation length exceeds 10 Mpc for E > 2 EeV 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. 16 Sommers FNAL

  17. UHE Photon Limits (strongly constrain top-down scenarios) Astroparticle Physics  31  (2009), 399 Astroparticle Physics 29 (2008), 243 Astroparticle Physics 27 (2007), 155 Sommers FNAL 17

  18. Enhancements at Auger South HEAT: High Elevation Auger Telescopes AMIGA: Auger Muon and Infill Ground Array , AERA: Auger Engineering Radio Array Sommers FNAL 18

  19. Summary Deployment is complete for the Auger Observatory in Argentina Important science results: There IS a suppression of the energy spectrum Trans-GZK arrival directions correlate with local structure Energy 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 sphere Intriguing trend in Xmax distributions for energies up to 30 EeV New Auger limits on diffuse neutrinos New Auger limits on diffuse photons (ruling out generic top-down models) Sommers FNAL 19

  20. Auger North Auger North targets the key energy regime above 55 EeV Exploit 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 sources Study the spectra of the brightest sources or regions individually Study cosmic magnetic fields by spectrometry Constrain 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) Sommers FNAL 20

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