Telescope Array
Telescope Array
Telescope Array
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G.T. Zatsepin memorial readings,Moscow, June 10, 2011Status and results of the<strong>Telescope</strong> <strong>Array</strong> experimentSergey TroitskyINR, Moscowthe <strong>Telescope</strong> <strong>Array</strong> collaboration
Plan1. The <strong>Telescope</strong> <strong>Array</strong> detection methods2. Primary energy estimation and cosmic-rayspectrum3. Primary composition: protons or heavy nuclei?4. Arrival directions: search for anisotropies5. Search for primary photons
Ultra-high-energy cosmic rays:experiments
<strong>Telescope</strong> <strong>Array</strong> Collaboration
the <strong>Telescope</strong> <strong>Array</strong>is not an array of telescopes…S=3 m2
Surface detectorScintillatorDetectorson a 1.2 kmsquare grid• Power: Solar/Battery• Readout: Radio• Self-calibrated: muon background• Operational: 3/2008
A typical Surface-Detector event2008/Jun/25 - 19:45:52.588670 UTCGeometry Fit (modified Linsley)Lateral DensityDistribution Fit(AGASA LDF)r = 800m
A typical Surface-Detector eventtiming recorded ateach station
TA fluorescent detector 1:Middle Drum (refurbished HiRes I)
TA fluorescent detectors 2 and 3:Long Ridge and Black Rock Mesa (brand new)
A typical fluorescent-detector eventEvent DisplayBlack Rock MesaFluorescenceDirect (Cerenkov)Rayleigh scatt.Aerosol scatt.Monocular timing fitReconstructed Shower Profile
TA fluorescence detectors working togetherRefurbishedfrom HiRes-IObservationssince ~10/2007Middle Drum14 telescopes@station256 PMTs/camera5.2 m 2New FDsObservationsince~11/2007Long RidgeObservationsince ~6/2007Black Rock Mesa12 telescopes/station256 PMTs/cameraHamamatsu R9508FOV~15x18deg~1 m 26.8 m 2
Example of a TRIPLE STEREO HYBRID eventMD2008-10-26MDmonoBRmonoStereoBR&LRq [ o ] f [ o ] x[km] y[km]51.43 73.76 7.83 -3.1051.50 77.09 7.67 -4.1450.21 71.30 8.55 -4.88LRSDBR
energy estimation
Energy estimation:SD and FD see different parts of the showercore ~(50–100) mFD: core,electrons onlydistance between stations ~(1000–1500) mSD: periphery of the shower, sums up all particles
FD energy estimationdetection offluorescent photons• distance to the shower• atmospheric transparency• fluorescent yieldShower model• other particles• contribution of outer regionsexposure:shower+detector model• effective area• cutsenergy ofcore electronsfull energyspectrum
SD energy estimation: traditional (“the CIC method”)experimentsignal at detectoras a function of zenith anglefor identical showerseffective signal«if the showerwere vertical»Monte-Carlodepends of the shower modeland primary particle typeORcalibration toa different method(FD, air Cerenkov)averaging,systematicsenergycorresponding tothis effective signal
SD energy estimation: TAexperimentsignal at detectoras a function of zenith anglefor identical showerseffective signal«if the showerwere vertical»Monte-Carlodepends of the shower modeland primary particle typeORcalibration toa different method(FD, air Cerenkov)averaging,systematicswhich energycorresponds tothis effective signal
SD energy estimation: TAFULL MONTE-CARLO! QGSJET II PROTONS
SD energy estimation: why not CIC?because of excellent data/MC agreement!Haverah Park, AGASA, Yakutsk, Pierre Auger: CIC methodTheir motivation: MC does not describe well the shower developmentWHY WORKS in TA [at least for (0-45) degree zenith angles]?yet to be understood…• a bit of luck (relatively high altitude + plastic scintillators)??Haverah Park: water tanks low altitudeYakutsk, AGASA: plastic scintillators low altitudePierre Auger: water tanks high altitude• sophisticated MC (shower+detector, dethinning etc.)?
SD simulations: summary
SD simulations: dethinning
SD simulations: no-thinning
SD simulations: no-thinning
SD simulations: dethinning
SD simulations summary
SD energy estimation: TA
SD energy estimation
SD data/MC comparison
SD quality cuts• Good data fits: χ 2 /d.o.f. > 4.0 Pointing direction resolution
SD data/MC comparison
SD data/MC comparison
SD data/MC comparison
SD energy resolution
SD vs. FDSD energy: CORSIKAQGSJET-II protonsfull MCFD energy:MD mono,BRM, LR hybridNote: 19% systematic uncertainty
SD vs. FD
SD vs. FD energies:approaches to the contradictionAuger:correct method=FDuse FD normalization for SD events<strong>Telescope</strong> <strong>Array</strong>:study hybrids (work in progress)calibrate FD to electron beam from an accelerator (work in progress)currently use FD normalization for SD events…theory:new models of hadronic interactions?new models of electromagnetic cascades???details of systematics of the FD method
<strong>Telescope</strong> <strong>Array</strong>: FD calibration
<strong>Telescope</strong> <strong>Array</strong>: FD calibrationELS (electron light source = LINAC)a0.5Hz
<strong>Telescope</strong> <strong>Array</strong>: FD calibrationELS works!
RESULTS: COSMIC-RAY ENERGY SPECTRUM
TA SD spectrumSD energy recaled to FD energy
TA sees the GZK-like suppressiona
TA sees the GZK-like suppressiona cutoff or a step? not enough statistics
Other experiments see the GZK-like suppressionspectrum continuation excluded at6σ (HiRes), 10σ (Pierre Auger), 3.5σ (TA)
Spectra measured in various experimentsa
TA spectra (different techniques)
TA spectrum agrees with HiRes
RESULTS: PRIMARY COMPOSITION
Primary composition: protons or heavy nuclei?Yakutsk (muons):
Primary composition: protons or heavy nuclei?HiRes:Northern hemisphere, protonsAuger:Southern hemisphere, mixYakutsk:Northern hemisphere, mix
TA composition results:
Primary composition: protons or heavy nuclei?HiRes:Northern hemisphere, protonsAuger:Southern hemisphere, mixYakutsk:Northern hemisphere, mixTA:Northern hemisphere, protons
RESULTS: ARRIVAL DIRECTIONS
Anisotropy: data
Auger: AGN correlations
Auger: AGN correlations weakened
TAAGN correlationsTA preliminary
TA autocorrelation
TA correlations with the large-scale structurematter in the Universe distributed anisotropicallyat the scales of UHECR propagationastrophysical sources should follow the matter distribution• arrival directions follow the matter distribution?‣ trace the distribution of galaxies (2MASS XSCz)‣ assume injection spectrum‣ account for propagation‣ get expected skymap‣ compare with data• first observed in 1990s in Yakutsk data• may explain Auger AGN correlations without AGNs
TA correlations with the large-scale structure
TA correlations with the large-scale structure
RESULTS: SEARCH for PHOTONS
TA photon search
TA photon search
TA photon search
TA future plans…
CONCLUSIONS
CONCLUSIONS• PRIMARY ENERGIES:‣ FD/SD disagreement (TA: 27%), origin to be studied‣ TA uses a new SD energy method (MC, not CIC)• SPECTRUM:‣ TA=HiRes‣ Auger vs. TA vs. Yakutsk disagree in normalization‣ HiRes, Auger, TA agree on the GZK-like suppression‣ insufficient statistics to study the shape at E>10 20 eV• COMPOSITION: contradictory results‣ TA, HiRes : protons‣ Auger, Yakutsk : mix• ANISOTROPY:‣ Auger AGN correlations weak, TA AGN: consistent with isotropy‣ Autocorrelations: consistent with isotropy‣ Large-scale structure: weak evidence at E>57 EeV• NO PHOTONS FOUND
stereo: protons or nuclei?
stereo: protons or nuclei?a
Photons?
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