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

2 Sommers FNAL 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

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

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 X max values for energies up to 30 EeV Sommers FNAL

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

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

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

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

9 The Auger Sky above 55 EeV 27 events as of November 2007 Science 318 (2007), 939 Astroparticle Physics 29 (2008), 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). Sommers FNAL Log(Likelihood)

10 Shower Depths of Maximum X max 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) Sommers Lodz Anisotropy

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

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 Sommers Lodz 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.

13 The Ascent of Exposure Logarithmic ScaleLinear Scale Linsleysx10 5 Linsleys Sommers Lodz TA

14 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 14 Sommers FNAL

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

16 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 Sommers FNAL

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

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

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 X max 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

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