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!
Pages to are hidden for
"GRaNDScan - Physics - University of Adelaide"Please download to view full document