The Pierre Auger Project

1
WIN05
?????O? Neutrinos
?????S?S Particle Astrophysics
2
Ultra-High Energy Cosmic Rays Status and
Perspectives
Weak Interactions and Neutrinos 2005 Delphi,
Greece June 6-10, 2005
Stéphane Coutu The Pennsylvania State University

• The Highest Energy Cosmic Rays
• Experimental Results
• Detection techniques
• Air shower arrays (e.g., AGASA)
• Air fluorescence technique (e.g., HiRes)
• A conundrum?
• Recent and Future Developments
• The Auger Observatory
• Telescope Array, other proposed efforts
• Current status and prospects

3
The Beginning
1015 eV (1939)
4
The Cosmic Ray Spectrum
1979-96 1979-83 1970s 1980s, 90s 1996- 1997-98 199
4-96 1990s 1990s 1990s
Fluxes rescaled by E2
gt1019 eV 1 per (km2 year sr)
gt1020 eV 1 per (km2 century sr)
5
The GZK Cutoff

• gt 4 x 1019 eV
• 50 from within 130 Mpc
• gt 1020 eV
• 50 from within 20 Mpc

ANISOTROPIES might be expected from nearby
sources
6
Possible Source Mechanisms

• Conventional
• Bottom Up
• Shock acceleration
• Jets hot spots
• Galaxy collisions
• Accretion flows
• Gamma Ray Bursts

• Exotic
• Top Down
• Topological Defects
• Monopoles
• New particles with interactions to evade GZK bound

7
Bottom-Up Acceleration
Hillas, Ann. Rev. As. Ap. 1984
Account for radiative losses within
the accelerating region (synchrotron losses,
photoreactions)

• UHE cosmic rays
• likely extragalactic
• (also Larmor radius,
• spectral structure near
• ankle)

8
Cosmic Ray Mass Composition
UHE cosmic rays extend a further 3 orders of
magnitude in energy
p
He
Fe
9
Techniques for UHECR Detection

• UHECR generate cascades (showers) in the
  atmosphere
• 1020 eV yields 1011 particles at maximum

• Shower front particles can be
• directly detected on the ground
• Showers excite nitrogen
• fluorescence, detectable on dark
• nights

10
Techniques for UHECR Detection
1. Generic Method (Auger) Detect the particles
directly Haverah Park 12 km2 270 km2
yr sr Yakutsk 25 km2 490 km2
yr sr AGASA 100 km2 2000 km2
yr sr BUT primary energy estimate is MODEL
DEPENDENT ?E/E 25
2. Fluorescence Light gives CALORIMETRIC measure
of energy of primary particle. ?E/E 20 Flys
Eye 930 km2 yr sr monocular 151 km2 yr
sr stereo HiRes 5000 km2 yr sr
monocular 2500 km2 yr sr stereo
11
Akeno Giant Air Shower Array
AGASA (Akeno, Japan) 100 km2 ground array
12
AGASA Spectrum
13
High Resolution Flys Eye
HiRes (Dugway, Utah) 2 N2 fluorescence sites
14
HiRes Spectrum 1999
Absorption Length of Atmosphere was set to 15 km
15
HiRes Spectrum 2002
Absorption Length of Atmosphere was changed to
25 km
A conundrum?
GZK cutoff seen?
16
HiRes vs AGASA
AGASA energies overestimated by 20?
Energy reconstruction dependent on
particle physics extrapolated by several
decades (AGASA estimate 25 systematic)
17
HiRes vs AGASA
HiRes profile fits sometimes poor
Fluorescence yield poorly understood
Atmospheric attenuation needs to be understood
and corrected for daily
18
AGASA UHECR Sky Map
4 10 1019 eV
gt 1020 eV
Galactic Plane
Supergalactic Plane
Clustering within 2.5
0.9 probability
19
HiRes UHECR Sky Map
HiRes 2004 point sources ruled out above 1019.5
eV in HiRes-I mono data
HiRes 2005 point sources ruled out above 4?1019
eV in an analysis of 57 AGASA 27 HiRes stereo
events
20
Results so far suggest
Status

• There are events with energies beyond
• 1020 eV seen by AGASA, Flys Eye and HiRes
• - BUT we are not sure of the fluxes
• The arrival directions seem rather isotropic
• - BUT there may be clusters
• Major problem is that flux above 1020 eV is
• 1 km-2 century-1 sr-1
• Need much larger, hybrid detector ? Auger!

21
Auger Observatory

• 10 years 3000 km2 yields 300 -500 events gt1020
  eV
• SOURCES? Two Observatories Necessary

22
Southern Hemisphere SiteArgentina
23
Auger Hybrid Detector
24
Surface Detectors
25
Surface Detector Deployment
26
Auger Surface Detectors
27
Haverah Park Heritage
A tank was opened at the end of project party
on 31 July 1987. The water shown had been in the
tank for 25 years but was quite drinkable!
28
Unique Problems
29
UHE Auger Event
May 21, 2004 34 tanks E1.2?1020
eV preliminary! ? 59?
30
PMT Traces
FADC Traces
1 µs
31
Fluorescence Detector
32
Fluorescence Detector
440 PMT camera 1.5 per pixel
corrector lens (aperture x2)
segmented spherical mirror
aperture box shutter filter UV pass safety curtain
Fluorescence detector at Los Leones
33
Fluorescence Event
34
Fluorescence Event
? 15?
E 2.5 1018 eV
Cerenkov contribution correction
raw
direct
Gaisser-Hillas form
scattered
35
FD Calibrations
36
Stereo Hybrid Event
37
Hybrid Reconstruction
0-25 degrees
25-45 degrees
45-60 degrees
Clear correlation between SD and FD energy
estimates
38
Hybrid Reconstruction
dR (m) d?0 () Mono 921 8.05 Hybrid 21 0.24
39
Auger Status June 05

• 793 surface detectors deployed (755 fully
  functional)
• 3 fluorescence detector buildings completed, 1
  under construction (15 telescopes fully
  instrumented)

40
Auger Deployment
41
UHE Exposures
42
Telescope Array

• Utah 2004-2008
• 3 N2 fluorescence detectors
• 576 scintillators
• 830 km2 (1/4 of one Auger site)
• Resolve AGASA/HiRes differences
• Possible low-energy extension (TALE) using HiRes
  telescopes and AGASA infill

Scintillator Array
FD Station
43
Simulated Auger Spectrum w/GZK Cutoff
20 months with full Auger Observatory
44
First Auger Spectrum
Total acceptance is ?? ? 1015 m2 sr s
45
First Auger Sky Map
46
Conclusions

• Highest energy cosmic rays origin is still a
  complete mystery!
• Large increases in data, and fresh particle
  physics input, are needed.
• Promising new experimental efforts.
• Auger Argentina site completion targeted for
  2006 Northern site (UT, CO) under discussion.
• Expect definitive measurement of UHE spectrum,
  sensitivity to point sources, composition,
  potential for new neutrino frontier.
• First Auger results end of June!

47
Top-Down Exotics
Exa Zetta Yotta
48
Horizontal Showers

• Flat and thin shower front
• Narrow signals
• Time alignment

• Curved and thick shower front
• Broad signals

49
Far Shower
Ground particle densities for 1020 eV p, 100 km
injection altitude, ? ? 80?
50
Deep Shower
Ground particle densities for 1019 eV p, 3 km
injection altitude, ? ? 80?
51
Geomagnetic Distortions
Geomagnetic distortion of the ground spot, at 80?
and 86? affects acceptance vs. energy.
52
Horizontal Shower

• January 6, 2002 8 tanks triggered (7 radioed
  information)
• Tank signals 5.6, 6.3, 6.8, 7.5, 16, 21, 35
  v.e.m.
• ? 82.9 ?1.2?, ? 130.4 ?1.3? (w/ magnetic
  corrections)
• E gt1019 eV

Far shower (not neutrino!)
53
Horizontal Shower
Best fit 83? seems to require gt 1019 eV (but
then would have expected more tanks fired)
54
Neutrino Spectrum