1. Existing and Planned UHE Cosmic Ray Experiments
GRaNDScan
Telescope Array
Existing and Planned UHE Cosmic Ray Experiments
Bruce Dawson University of Adelaide, Australia
OWL

2. Setting the scene - UHECR
ultra-high energy cosmic rays
most energetic particles known in the Universe
protons, atomic nuclei
macroscopic energies - up to 3x1020eV (50J) - and beyond?

3. AGASA experiment 6 doublets, 1 triplet within 2 deg cone
Arrival directions
very isotropic: galactic and extra-galactic magnetic fields scramble arrival directions, except at highest energies
possible clustering of rare particles above eV
AGASA experiment 6 doublets, 1 triplet within 2 deg cone

4. Possible Signal around 1018eV
AGASA experiment Hayashida et al. 1999
re-analysis of SUGAR experiment Bellido et al. 2001

5. Extensive Air Showers we can cope with very low event rates
at highest energies, EAS may contain at 1011 particles and cover tens of square kilometres at ground level

6. Typical measurements
From measurements of an EAS we can determine properties of primary cosmic ray
its energy
its arrival direction
an estimate of its mass (nucleon, nucleus, gamma-ray)
e.g. Fly’s Eye measurement of
air shower development
-trend towards lighter mass (protons) above 1018 eV

7. Greisen-Zatsepin-Kuzmin cut-off? AGASA HiRes
e.g. energy spectrum
current controversy over shape of spectrum above 1019eV
AGASA and HiRes observatories, each with similar exposures
is there a cut-off to the energy spectrum?
Greisen-Zatsepin-Kuzmin cut-off? AGASA HiRes

8. compilation of 30 years of measurements
Bahcall & Waxman Phys Lett B566,1 (2003)
compilation of 30 years of measurements
some of the disagreement removed by shifts in energy calibration
Clearly a need to “intercalibrate” techniques

9. AGASA - Akeno Giant Air Shower Array
JAPAN
100 square kilometres

10. AGASA detector station
111 plastic scintillator detectors,
each 2.2 square metres in area 27 also equipped with shielded muon detectors (0.5 GeV)

11. AGASA technique
energy from measurement of scintillator lateral distribution - signal at 600m from core (somewhat model dependent)
directions from fast timing - angular resolution 1-2 deg
mass estimates from measurement of muon content
scintillator signal
muons
One of AGASA’s highest energy events ( ) x 1020 eV

12. High Resolution Fly’s Eye
alternative optical technique - air fluorescence
air showers excite atmospheric nitrogen
fluorescence yield
between nm approx. 4 photons per shower particle per metre of track
The technique has a long history…

13. The First Fly’s Eye - New York 1967
Greisen, Bunner et al.
Sky & Telescope October 1967

14. Utah Fly’s Eye
Cassiday, Bergeson, Loh, Sokolsky et al.

15. Highest Energy Fly’s Eye Event
this technique is calorimetric
energy comes directly from integral of shower development profile (right)
but challenges include
atmospheric attenuation
fluorescence yield (T and P dependence)
detector calibration
shower size peaks at 200 billion particles
E = (3.2 +/- 0.9) x 1020 eV

16. High Resolution Fly’s Eye
One of two sites 13km apart - Dugway, western Utah Collecting area in excess of 3000km2 at highest energies
US/Australia collaboration

17. Mirror Units 2 metre diameter mirror, 256 phototubes in focal plane
a total of 67 mirror units at the two sites

18. Typical stereo HiRes event
stereo provides advantages over single-eye observations
improved shower geometry
two views of shower profile (energy)
checks of systematics

19. Mono operation Stereo operation 1997- 3600 hours
mono spectrum submitted, anisotropy studies ready for submission
Stereo operation
1999 -
some difficulties at Dugway
1500 hours
similar aperture to mono
3000km2 area

20. Pierre Auger Observatory

21. Collaboration: Northern hemisphere Millard county Utah, USA
Southern hemisphere:
Malargüe
Provincia de Mendoza
Argentina
Collaboration:
>250 researchers from 50 institutions and 18 countries:
Argentina, Australia, Bolivia, Brazil, China, Czech Republic, France, Germany, Greece, Italy, Mexico, Poland, Russia, Slovenia, Spain, United Kingdom, USA, Vietnam

22. The Observatory Mendoza Province, Argentina 3000 km2, 875 g cm-2
1600 water Cherenkov detectors 1.5 km grid
4 fluorescence eyes -total of 24 telescopes each with 30o x 30o FOV
65 km

23. Extensive Air Shower
<8 km>
…not to scale

24. Pierre Auger - a major step
Need high statistics
large detection area : 2 x3000 km²
Uniform sky coverage
2 sites located in each hemisphere Argentina and USA
Hybrid detector :
surface array (water Cerenkov tanks)
+ fluorescence detector  Good energy and pointing resolution, Improved sensitivity to composition
Energy cross calibration

25. The Engineering Array 2001/2
1020 eV Shower
The Engineering Array
Auger Campus
Engineering Array
40 Surface detector stations
2 Fluorescence cameras overlooking the array

26. Engineering Array

27. Auger Surface Detectors
Three 8” PM Tubes
Plastic tank
White light diffusing liner
De-ionized water
Solar panel and electronic box
Comm antenna
GPS antenna
Battery box

28. Surface Detectors
1019eV proton
SD water Cherenkov detectors measure muon, electron and gamma components of EAS, the latter especially important at large core distances

29. Surface Detector Resolution
SD Angular resolution: E > 1019eV
q (deg)
Proton/Iron
Photon
E>1019eV
E>1020eV
20o
1.1o
0.6o
4.0o
40o
0.5o
2.5o
60o
0.4o
0.3o
1.0o
80o
0.2o
space angle containing 68% of events

30. Surface Detector Resolution
Energy determined from fitted density at 1000m, r(1000). Conversion factor from simulations; averaged for p and Fe primaries. E > 1019 eV rms E resolution ~12% (assuming p/Fe mixture)
Proton
Iron
photon

31. SD Aperture and Event Rate
Eo (eV)
Trig Aperture km2sr
Rate per year > Eo
1018
3x1018
2200
15000
1019
7200
5150
2x1019
7350
1590
5x1019
490
1020
100
2x1020 30
Zenith < 60o, based on AGASA spectrum (Takeda et al 1998)
(Zenith > 60o adds about 50% to event rate)

32. Auger Southern Site
Hybrid reconstruction works when a shower is recorded by the surface array and at least one eye
This multiple-eye design reduces our reliance on precise knowledge of atmospheric attenuation of light
Mean impact parameter at 1019eV is 14.7km

33. N2 fluorescence:
≈ 4 photons/m m.i. part.
 dE/dx
filter

34. The completed FD building will house 6 telescope/ camera arrays

35. 11m2 segmented spherical Schmidt mirror, 30°30°

36. UV-Filter nm
installed at Los Leones (Malargüe) and taking data
11 m2 mirror
camera 440 PMTs
corrector lens

37. Hybrid Reconstruction of Axis
good determination of shower axis is vital for origin studies, but also vital as first step towards good energy and mass composition assignment
use eye pixel timing and amplitude data together with timing information from the SD.
GPS clocks in SD tanks and at FDs.
Hybrid methods using one eye give angular resolution comparable to “stereo” reconstruction

38. Hybrid Reconstruction Quality
E(eV)
Ddir (o)
DCore (m)
DE/E (%)
DXmax g/cm2
1018
0.7 60 13 38
1019
0.5 50 7 25
1020 6 24
statistical errors only
zenith
angles < 60O
68% error bounds given
detector is optimized for 1019eV, but good Hybrid reconstruction quality at lower energy

39. Simulated Hybrid Aperture
Hybrid Trigger Efficiency
“Stereo” Efficiency
Note the significant aperture at 1018eV, and the stereo aperture at the higher energies
Trigger requirement: at least one eye triggering on a track length of at least 6 degrees; two surface detectors. q < 60o
Hybrid Aperture = Hybrid Trigger efficiency x 7375 km2sr

40. “high” energy Hybrid event
170067

41. 170067

42. Light received at FD
Inferred Shower Profile
E = 1.5 x 1019eV

43. Auger Schedule strong and efficient collaboration
engineering array was a great success, we have recorded some beautiful events.
two FD buildings have been constructed, fully instrumented by end of 2003
next 100 SD installation complete within 2 months (soon stereo-hybrid)
expect full observatory complete during 2005
we hope construction of Northern Auger will begin in 2-3 years

44. COMPARISON OF EXPERIMENTS
(Katsushi Arisaka, UCLA)

45. (Katsushi Arisaka, UCLA)

46. Telescope Array Project
Japan/US collaboration. Japanese funding for Phase 1 has just been announced. A hybrid detector system
20 km
UTAH, USA
24 x 24 scintillators (3m2)
with 1.2km spacing
(850 square km)
3 x Fluorescence
stations with 120 deg azimuthal view

47. Scintillator Prototype:
　　　　50 cm x 50 cm, 1cm thick
　　　　　　Wave Length Shifter Fiber readout
　　　　50 modules used in L3 for 2.5 years.
cutting 1.5 mm deep groove
Final: 3 m2 by 2 PMT readout.
WLS: BCF-91A
（ 1 mm Φ ）
M. FUKUSHIMA, ICRR Tokyo

48. Fluorescence Detector： Prototypes have been developed.
M. FUKUSHIMA, ICRR Tokyo
Fluorescence Detector：　Prototypes have been developed.
1 0 x 1 0 FoV / PMT
16 bit, 200 ns + DSP
3 m Φ spherical

49. TA Phase I Performance
M. FUKUSHIMA, ICRR Tokyo
Experiment
Aperture
(km2 sr)
Rel.
Angular
Resolution
AGASA
162
(=1)
1.60
TA: 24 x 24 ground array
1371
(9)
~1.00
TA: Fluorescence
670
(4)
0.60
TA: Hybrid Measurement
137
(1)
0.40
one goal: to intercalibrate scintillator and fluorescence techniques
Phase I ( ) US$15M
Phase II ( ): eight full fluorescence stations, effective aperture 50 x AGASA

50. GraNDScan
GRaNDScan
Does the Galactic Centre region contain a 1018 eV cosmic accelerator? Proposal for a new southern hemisphere observatory
AGASA experiment Hayashida et al. 1999
re-analysis of SUGAR experiment Bellido et al. 2001

51. GraNDScan
GRaNDScan
E. Loh (Utah/Maryland), S. Westerhoff (Columbia) et al.
plan for two fluorescence sites (one movable) with particular sensitivity to eV
low power electronics being developed to allow one eye to be solar powered, new micro-channel plate pmts being evaluated
one possible site, Woomera, South Australia (home of CANGAROO TeV gamma-ray observatory)
SEE POSTER by Gene Loh et al.

52. COMPARISON OF EXPERIMENTS
(Katsushi Arisaka, UCLA)

53. one of two planned space-based observatories
planned for operation in the early years of next decade
ESA / NASA
deployment on the International Space Station
Italy, France, Germany, Portugal, Japan, USA, UK

54. A FLUORESCENCE OBSERVATORY
Over a year EUSO
will achieve full-sky coverage - important
for anisotropy study

56. review in September, hope to commence Phase B in January
Dear Prof. Dawson,
Thanks for your interest in EUSO.
We are currently preparing the documentation, due for the end of July, for
the end of Phase A ( concetypual design) to submit to ESA (European Space
Agency). We will have a review at the middle of September and we hope to get
in the Phase B ( esecutive design) for the begining of the next year.
You can find general information on the EUSO mission on the web:
If you need specific information on whatever you need, please do not
hesitate to contact me.
Sincerely
Oscaldo Catalano

59. Experimental Challenges
space based!
mono observations - Cerenkov reflection helps
atmospheric monitoring, including aerosols and clouds (lidar on ISS)
UV airglow
ozone absorption severe below 330nm

60. COMPARISON OF EXPERIMENTS
(Katsushi Arisaka, UCLA)

61. NASA + U.S. universities

65. Conclusions
a revived interest in the UHE cosmic rays in the past decade - since the publication of the 3.2 x 1020eV Fly’s Eye event
the Fluorescence method is now a mature technique and its advantages are being recognised
the future looks bright!