1 Roma Meeting: June 2007 Recent results from the Pierre Auger Observatory (and comparisons with AGASA and HiRes) Alan Watson University of Leeds

2 Czech Republic France Germany Italy Netherlands Poland Portugal Slovenia Spain United Kingdom Argentina Australia Brasil Bolivia* Mexico USA Vietnam* *Associate Countries ~300 PhD scientists from ~70 Institutions and 17 countries The Pierre Auger Collaboration Aim: To measure properties of UHECR with unprecedented statistics and precision – necessary even if no disagreement

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

4 Present situation (April 13, 2007) Present situation (April 13, 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 30 May 2007

5 GPS Receiver and radio transmission

6 UV optical filter (also: provide protection from outside dust) Camera with 440 PMTs (Photonis XP 3062) Schmidt Telescope using 11 m 2 mirrors

7 θ~ 48º, ~ 70 EeV Flash ADC traces Lateral density distribution Typical flash ADC trace at about 2 km Detector signal (VEM) vs time (µs) PMT 1 PMT 2 PMT µs 18 detectors triggered

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

9 79 degrees

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

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

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

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

14 titi Geometrical Reconstruction

15 Angular and Spatial Resolution from Central Laser Facility Laser position – Hybrid and FD only (m)Angle in laser beam /FD detector plane 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 Energy Determination with Auger 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 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 %. Zenith angle ~ 48º Energy ~ 70 EeV

18 A Hybrid Event

19 S 38 vs. E(FD) 387 hybrid events Absolute value of FD calibration uncertain ~ 14% Nagano et al, FY used

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

21

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

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

24

km 2 sr yr ~ 0.8 full Auger year Exp Obs > / > / Spectrum from Surface Detectors

26 Ankle? Comparisons of residuals against an arbitrary spectrum

27 Spectrum from very inclined events

28 Calibration curve for Inclined showers

29 Energy Spectrum from 60 °<  < 80°: 734 events 1510 km 2 sr yr

30 Blue: < 60° Black: inclined

31 titi A ‘hybrid’ spectrum

32 Triggering probability for Hybrid Events

33 Lunar Cycles

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

35

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

37 Teshima: Roma 2006

38 HiRes Group: astro-ph/ /- 0.7

39

40 Plot of residuals of individual spectra compared to standard, J s = 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 ( /- 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 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. astro-ph/ Physics Letters B 2005

43 Exposure AGASA ~1700 HiResI “3-4 times AGASA” Auger 6675  > 4 x > 7x x x > x x x Integral Rates: km -2 yr -1 sr -1

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

45

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

47 and few photons at high energy Ankle Fluctuations in X max to be exploited

48

49 Jump to 66

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

51

52 Knee >10 19 eV 1 km -2 sr -1 year -1 air-showers after Gaisser Hadronic Physics Ankle

53 Models describe Tevatron data well - but LHC model predictions reveal large discrepancies in extrapolation. Could there be surprises in the hadronic physics? James L. Pinfold IVECHRI E T (LHC) E(LHC)

54 Prospects from LHCf

55 LHC measurement of  TOT expected to be at the 1% level – useful in the extrapolation up to UHECR energies The p-p total cross-section 10% difference in measurements of Tevatron Expts: James L. Pinfold IVECHRI (log s) 

56 Summary: Spectrum: ankle and steepening seen in model- independent measurement and analysis But what does this all mean? Is the ankle marking a galactic/extra-galactic change? Have we seen the GZK effect? Or is it a ‘bump’ from a more local effect? Are the accelerators just ‘tired’? Can we deduce much from propagation models? Measuring MASS is crucial: mixed at highest energy? Need a point source (or some evidence of anisotropy) – and/or more insight about hadronic interactions