Roma Meeting: June 2007

1. Roma Meeting: June 2007 Recent results from the Pierre Auger Observatory (and comparisons with AGASA and HiRes) Alan Watson University of Leeds a.a.watson@leeds.ac.uk

2. The Pierre Auger Collaboration Aim: To measure properties of UHECR with unprecedented statistics and precision – necessary even if no disagreement

3. Shower Detection Methods ~1° Nitrogen fluorescence The Design of the Pierre Auger Observatory marries these two well-established techniques 300 – 400 nm Fluorescence in UV → AND OR Array of water-Cherenkov or scintillation detectors Due to Enrique Zas 11

4. Present situation (April 13, 2007) 30 May 2007 1410 (1357 filled) SD stations deployed with 1304 taking data (300507) OVER 80% All 4 fluorescence buildings complete, each with 6 telescopes AIM: 1600 tanks

5. GPS Receiver and radio transmission

6. Schmidt Telescope using 11 m2 mirrors UV optical filter (also: provide protection from outside dust) Camera with 440 PMTs (Photonis XP 3062)

7. Typical flash ADC trace at about 2 km Detector signal (VEM) vs time (µs) Lateral density distribution PMT 1 PMT 2 PMT 3 θ~ 48º, ~ 70 EeV 18 detectors triggered Flash ADC traces Flash ADC traces -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 µs

8. θ~ 60º, ~ 86 EeV Flash ADC Trace for detector late in the shower Lateral density distribution PMT 1 PMT 2 PMT 3 Flash ADC traces 35 detectors triggered Much sharper signals than in more vertical events leads to ν- signature -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 µs

9. 79 degrees

10. Laser Facilities (April 13, 2007) 30 May 2007 XLF There are also 2 laser facilities, CLF and XLF Steerable YAG lasers to mimic 100 EeV CLF

11. The Central Laser Facility of the Pierre Auger Observatory 355 nm, frequency tripled, YAG laser, giving < 7 mJ per pulse: GZK energy

12. •LIDAR at each eye •cloud monitors at each eye • central laser facility • regular balloon flights Atmospheric Monitoring steerable LIDAR facilities located at each FD eye Balloon probes  (T,p)-profiles LIDAR at each FD building • light attenuation length • Aerosol concentration (Mie scattering)

13. FD reconstruction Signal and timing Direction & energy Pixel geometry shower-detector plane

14. ti Geometrical Reconstruction

15. Angular and Spatial Resolution from Central Laser Facility Angle in laser beam /FD detector plane Laser position – Hybrid and FD only (m) Mono/hybrid rms 1.0°/0.18° Mono/hybrid rms 570 m/60 m

16. ARRIVAL DIRECTION DISTRIBUTION FROM AUGER • No significant emission from Galactic Centre • No broadband signals – e.g. Dipole – at any energy • above 1 EeV • e.g 1 < E < 3 EeV, Amplitude < 0.7% • No clustering of the type claimed by AGASA • No signal from BL Lacs as possibly seen by HiRes Summary:Previous Claims have not been confirmed BUT, two ‘prescriptions’ are currently being tested – but I cannot tell you what they are

17. Zenith angle ~ 48º Energy ~ 70 EeV Energy Determination with Auger The energy scale is determined from the data and does not depend on a knowledge of interaction models or of the primary composition – except at level of few %. The detector signal at 1000 m from the shower core – S(1000) - determined for each surface detector event S(1000)is proportional to the primary energy

18. A Hybrid Event

19. S38 vs. E(FD) Absolute value of FD calibration uncertain ~ 14% Nagano et al, FY used 387 hybrid events

20. Precision of S(1000) improves as energy increases S(1000) 10 EeV

22. % (Outdated) Summary of FD systematic uncertainties ~ 14% Note: Activity on several fronts to reduce these uncertainties (to be updated)

23. Note: Activity on several fronts to reduce these uncertainties Summary of systematic uncertainties New version from Bruce Dawson’s Merida talk

25. Spectrum from Surface Detectors • Exp Obs >1019.6 132 +/- 9 58 > 1020 30+/- 2.5 2 5165 km2 sr yr ~ 0.8 full Auger year

26. Comparisons of residuals against an arbitrary spectrum Ankle?

27. Spectrum from very inclined events

28. Calibration curve for Inclined showers

29. Energy Spectrum from 60 °<  < 80°: 734 events 1510 km2 sr yr

30. Blue: < 60° Black: inclined

31. ti A ‘hybrid’ spectrum

32. Triggering probability for Hybrid Events

33. Lunar Cycles

34. Hybrid Spectrum: clear evidence of the ‘ankle’ at ~ 4 x 1018 eV -3.1 +/- 0.2

36. Surface Detectors Energy Estimates are model and mass dependent Recent reanalysis has reduced number > 1020 eV to 6 events Takeda et al. ApP 2003

37. Teshima: Roma 2006

38. - 5.1 +/- 0.7 HiRes Group: astro-ph/0703099

40. Plot of residuals of individual spectra compared to standard, Js = A E-2.6

41. Immensely important IF it was to be established • that slopes at highest energy are different in • northern(- 5.1+/- 0.7) and • southern hemispheres (- 4.1 +/- 0.4) • But, MUCH TOO EARLY TO DRAW CONCLUSIONS • Uncertainties about HiRes aperture • Poorer energy and angular resolution • in HiRes than Auger • Low number of events – • and no more to come to from HiRes • Issue will be addressed with more Auger data

42. astro-ph/0703099 The HiRes aperture is not easy to compute and requires assumptions about the spectral index and the mass composition in regions where it has not been measured. Physics Letters B 2005

43. Integral Rates: km-2 yr-1 sr-1

44. Inferring the Primary Mass: Crucial for Interpretation Variation of Depth of Maximum with Energy p Xmax Key is energy per nucleon ************************ Fe log E protons nuclei neutrinos photons all are expected at some level - at different energies

46. Elongation Rate measured over 2 decades in energy Fluctuations in Xmax yet to be explored and exploited

47. and few photons at high energy Ankle Fluctuations in Xmax to be exploited

49. Jump to 66

50. Comparison of data with models of origin and propagation Steepening affected by over- and under-densities Berezinsky et al. argue that the dip is caused by γ + p  p + e+ + e- Berezinsky et al Phys Rev D 74 (2006)