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Very Large Volume Neutrino Telescope Workshop Athens 13 – 15 October 2009

Very Large Volume Neutrino Telescope Workshop Athens 13 – 15 October 2009. Recent Results on Ultra High Energy Cosmic Rays Alan Watson University of Leeds a.a.watson@leeds.ac.uk. Outline: Results on Energy Spectrum: HiRes and

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Very Large Volume Neutrino Telescope Workshop Athens 13 – 15 October 2009

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  1. Very Large Volume Neutrino Telescope WorkshopAthens 13 – 15 October 2009 Recent Results on Ultra High Energy Cosmic Rays Alan Watson University of Leeds a.a.watson@leeds.ac.uk

  2. Outline: Results on Energy Spectrum: HiRes and Auger Results on Anisotropy Mass Composition Implications for UHE neutrino astronomy - but will not discuss Auger limits on neutrinos

  3. 400 physicists 18 countries ~90 Institutions Spokesperson: Giorgio Matthiae 1390 m above sea-level or ~ 875 g cm-2

  4. Auger Exposure nearly doubled since Mérida 12,790 km2 sr yr > 1019 eV: 4440 (HiRes stereo: 307 > 5 x 1019 eV: 59 : 19 > 1020 eV: 3 : 1) • HiRes Aperture: X 4 at highest energies • X 10 AGASA • TA area about ¼ Auger and exposure 0.5 AGASA

  5. A Hybrid Event • Energy Estimate • from area under • curve • + Missing energy • (2.1 ± 0.5) x 1019 eV

  6. f = Etot/Eem 1.17 f 1.07 Etot (log10(eV))

  7. Auger Energy Calibration 785 EVENTS log E (eV)

  8. Energy Spectrum from Auger Observatory SD + FD Lodz ICRC 2009 Schuessler HE 0114 Five-parameter fit: index, breakpoint, index, critical energy, normalization Above 3 x 1018 eV, the exposure is energy independent: 1% corrections in overlap region 8

  9. The Auger Energy Spectrum – compared with models ICRC 2009 Lodz Schuessler HE 0114 Above 3 x 1018 eV, the exposure is energy independent: ~1% corrections in overlap region 9

  10. HiRes Spectrum: Sokolsky,Trondheim Monocular spectra - HiRes I and II HiRes I - largest statistics, limited elevation angle viewing = high threshold energy HiRes II - better low energy response Stereo spectrum - best geometrical and energy resolution – use as reference

  11. Monocular and Stereo Aperture

  12. Stereo Geometrical Resolution

  13. Mono and Stereo Spectra Mono – HR1 and HR2 “The spectra measured using the monocular and stereo methods agree very well” Abassi et al: AstroParticle Phys 32 53 2009 Stereo

  14. Comparison of Slopes and break points for HiRes and Auger

  15. Residuals with respect to slope of 2.74 through this data point at log e = 18.65

  16. ANISOTROPY Situation as at November 2007: Science and Astroparticle Physics 27 events

  17. The Auger Sky above 60 EeV Comparison with Swift-BAT AGN density map Simulated data sets based on isotropy (I) and Swift-BAT model (II) compared to data (black line/point). Aublin HE 0491 ICRC Lodz 2009 22

  18. Mass Composition Indications • Most unexpected result from Pierre Auger Observatory so far

  19. Some Longitudinal Profiles measured with Auger

  20. More Longitudinal Profiles measured with Auger

  21. Data and MC Cuts HiRes Large fraction of the data used – in contrast to Auger approach Zenith angle < 70 deg Psuedo-distance to HiRes-2 > 10 km. Xmax bracketed in HiRes-2 FOV Energy > l018.2 eV Loose chi-sq profile fit and Xmax uncertainty cuts.

  22. Elongation rate corrected for detector acceptance and comparison with previous results

  23. Xmax fluctuations data and p QGSJET02: HiRes Auger – from above Xmax resolution

  24. J Belz (HiRes): Blois June 2009

  25. Fukushima: Rapporteur Talk at Lodz

  26. Probably now little doubt that a steepening in the cosmic ray spectrum has been found - HiRes and Auger data agree reasonably well BUT, it may be premature to jump to the conclusion that this is really the GZK-effect – energy limit in sources? Anisotropy is the key – but many more data needed BUT:What can we learn from the AGASA data? I do not believe that the measurements on the ground are in error: The data are surely telling us something

  27. Energy Estimates are model and mass dependent Takeda et al. ApP 2003

  28. Comment and Speculation • Effort should be made to understand why ground array • energy estimates are not in agreement with energy • spectra that are based on fluorescence detection • Does the multiplicity become very large at the highest • energies? • Maxima would be higher in atmosphere • Fluctuations would be smaller • More rapidly rising cross-section cannot be excluded • Need measurements closer than 300 m from core

  29. Summary • Suppression of spectrum slope above 40 EeV • seems certain – but is it really GZK-effect? • Anisotropy suggests around 40% correlation with • local matter density above 55 EeV • Composition situation is puzzling. Heavy nuclei at higher • energies are not excluded. Big HiRes/Auger differences • Large fraction of heavy nuclei would impact on predictions • of neutrino fluxes

  30. Do we already have evidence for exotic physics? Reminder: Initial Estimate of Temperature was 3.5 +/- 1 K

  31. Differential Spectra: Sample data AG/Au = 2.30 AG/HiR = 1.76 AG/Au = 3.75 AG/HiR = 2.90

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