GRaNDScan - Physics - University of Adelaide

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					                                 GRaNDScan


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




                OWL
     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?
                      Arrival directions
• very isotropic: galactic and extra-galactic magnetic
  fields scramble arrival directions, except at highest
  energies
• possible clustering of rare particles above 1019.6 eV




                                 AGASA experiment
                            6 doublets, 1 triplet within 2 deg cone
Possible Signal around 1018eV

                         AGASA experiment
                         Hayashida et al. 1999




  re-analysis of SUGAR
  experiment
  Bellido et al. 2001
             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
            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
              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              Greisen-Zatsepin-Kuzmin cut-off?
  spectrum?
                                 AGASA      HiRes
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
AGASA - Akeno Giant Air Shower Array
                              JAPAN




  100 square kilometres

     1992-2004
           AGASA detector station




111 plastic scintillator detectors,
each 2.2 square metres in area

27 also equipped with shielded
muon detectors (0.5 GeV)
                             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 (2.1+0.5 -0.4) x 1020 eV
    High Resolution Fly’s Eye
• alternative optical technique - air fluorescence
• air showers excite atmospheric nitrogen

                                fluorescence yield
                                between 300 - 400nm

                                approx. 4 photons per
                                shower particle per metre
                                of track



        The technique has a long history…
The First Fly’s Eye - New York 1967
                               Greisen, Bunner et al.




Sky & Telescope October 1967
Utah Fly’s Eye 1981-1993
       Cassiday, Bergeson, Loh, Sokolsky et al.
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)   • shower size peaks at 200
   • detector calibration      billion particles
                             • E = (3.2 +/- 0.9) x 1020 eV
          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
                               Mirror Units




• 2 metre diameter mirror, 256
  phototubes in focal plane

• a total of 67 mirror units at the
  two sites
 Typical stereo
  HiRes event
• stereo provides
  advantages
  over single-eye
  observations
  – improved
    shower
    geometry
  – two views of
    shower profile
    (energy)
  – checks of
    systematics
               • Mono operation
                 – 1997-
                 – 3600 hours
                 – mono spectrum
                   submitted,
                   anisotropy studies
                   ready for
                   submission
               • Stereo operation
3000km2 area     – 1999 -
                 – some difficulties at
                   Dugway
                 – 1500 hours
                 – similar aperture to
                   mono
Pierre Auger Observatory
                                  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
        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
Extensive Air Shower


   <8 km>
        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
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
Engineering Array
             Auger Surface Detectors
          Solar panel and   GPS
          electronic box    antenna
                                         Comm
                                         antenna
   Three 8”
   PM Tubes




                                           Battery
White light
                                           box
diffusing liner


  De-ionized water                    Plastic tank
                 Surface Detectors
                    1019eV proton




• SD water Cherenkov detectors measure muon,
  electron and gamma components of EAS, the latter
  especially important at large core distances
Surface Detector Resolution
 • SD Angular resolution: E > 1019eV

   q (deg)        Proton/Iron       Photon
             E>1019eV E>1020eV E>1019eV
     20o        1.1o       0.6o      4.0o
     40o        0.6o       0.5o      2.5o
     60o        0.4o       0.3o      1.0o
     80o        0.3o       0.2o      1.0o


           space angle containing 68% of events
     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


                                           Iron
                          Proton

            photon




      rms E resolution ~12% (assuming p/Fe mixture)
     SD Aperture and Event Rate
                        Trig Aperture Rate per year
            Eo (eV)
                            km2sr         > Eo
              1018           0             0
             3x1018        2200          15000
              1019         7200           5150
             2x1019        7350           1590
             5x1019        7350           490
              1020         7350           100
             2x1020        7350            30
• Zenith < 60o, based on AGASA spectrum (Takeda et al 1998)
        • (Zenith > 60o adds about 50% to event rate)
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
N2 fluorescence:
≈ 4 photons/m m.i. part.
 dE/dx


         filter
The completed FD building will house
6 telescope/ camera arrays
11m2 segmented
spherical Schmidt
mirror, 30°30°
                   UV-Filter
installed at Los   300-400 nm
Leones
(Malargüe) and
taking data
                                           11 m2
                                camera     mirror
                                440 PMTs
corrector
lens
     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
  Hybrid Reconstruction Quality

                      DCore              DXmax
  E(eV)   Ddir ( )o
                              DE/E (%)
                       (m)               g/cm2

  1018      0.7        60       13        38     statistical
                                                 errors only

  1019      0.5        50        7        25     zenith
                                                 angles < 60O

  1020      0.5        50        6        24

• 68% error bounds given
• detector is optimized for 1019eV, but good Hybrid
  reconstruction quality at lower energy
                 Simulated Hybrid Aperture


Hybrid Trigger                                                       “Stereo”
Efficiency                                                           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
         “high” energy Hybrid event




170067
170067
 Light
 received at
 FD




 Inferred
 Shower
 Profile
E = 1.5 x 1019eV
                     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
COMPARISON OF EXPERIMENTS




                 (Katsushi Arisaka, UCLA)
(Katsushi Arisaka, UCLA)
               Telescope Array Project
• Japan/US collaboration. Japanese funding for Phase 1 has
  just been announced. A hybrid detector system

                                            UTAH, USA




 24 x 24 scintillators (3m2)
 with 1.2km spacing
 (850 square km)

 3 x Fluorescence
 stations with 120 deg
 azimuthal view                20 km
cutting 1.5 mm deep groove    Scintillator Prototype:
                                     50 cm x 50 cm, 1cm thick
                                     Wave Length Shifter Fiber readout
                                     50 modules used in L3 for 2.5 years.




      WLS: BCF-91A           Final: 3 m2 by 2 PMT readout.
       ( 1 mm Φ )




                                                     M. FUKUSHIMA, ICRR Tokyo
                                          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
                                              M. FUKUSHIMA, ICRR Tokyo

              TA Phase I Performance
                            Aperture                  Angular
           Experiment                   Rel.
                            (km2 sr)                 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 (2004-2009) US$15M
 • Phase II (2010-2015): eight full fluorescence
   stations, effective aperture 50 x AGASA
                                         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
                                GraNDScan
                                   GRaNDScan

• E. Loh (Utah/Maryland), S. Westerhoff (Columbia) et al.
• www.nevis.columbia.edu/grandscan

• plan for two fluorescence sites (one movable) with
  particular sensitivity to 1017 - 10 18.5 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.
COMPARISON OF EXPERIMENTS




                 (Katsushi Arisaka, UCLA)
• 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
A FLUORESCENCE
  OBSERVATORY




 Over a year EUSO
 will achieve full-sky
 coverage - important
 for anisotropy study
review in September,
hope to commence
Phase B in January
       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
COMPARISON OF EXPERIMENTS




                 (Katsushi Arisaka, UCLA)
NASA + U.S. universities
                               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!

				
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posted:3/29/2013
language:English
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