VIIIth International Workshop on the Dark Side of the Universe, Buzios STUDY OF THE ULTRA HIGH ENERGY COSMIC RAYS WITH THE AUGER DATA OVERVIEW OF THE RESULTS H. Lyberis on behalf of the Pierre Auger Collaboration 13/06/2012 1
THE COSMIC RAY SPECTRUM AUGER 2
THE AUGER Hybrid detection Complementary EAS detection techniques In the pampa near Malargüe (Argentine) 1400m a.s.l. - latitude: 35 Lateral profile Longitudinal profile Fluorescence detector Surface detector (water Cherenkov) Accurate measurements Cross-calibration for the energy Resolutions angular resolution : 1-3 absolute energy uncertainty : 22% relative energy resolution : 16-12% 3
THE AUGER Fluorescence detector 4 eyes - 6 telescopes by eye Measure the photons generated by the EAS, exciting the N2 of the air Calorimetric measurement of E (negligible dependency of hadronic models) % of duty cycle (clear moonless nights) Low energy extension : HEAT Requires a monitoring of the atmosphere (P, T, aerosol content, clouds ) For hybrid events Esat = 1 EeV Selection of events Fiducial cuts to have the same acceptance for p/fe, FOV(E) Quality cuts on the the profile reconstruction Atmospheric conditions exposure determined by MC 4
THE AUGER Surface detector 1660 surface detectors triangular grid (1.5 km) covering 3000 km 2 water Cherenkov tanks full efficiency @ Esat = 3 EeV low energy extension : infill Selection of events based on the operational tanks configuration geometrical exposure 2 different reconstructions for < 60 & > 60 5
SPECTRUM E > Flux suppression GZK prediction : interaction of the CRs/γCMB Emax at the source p : pion-production nuclei : photo-dissociation E The ankle Ankle model Transition from Gal to X-Gal Dip model pure proton component from X-Gal src Pair production in 18-4x 19 ev 6
ANISOTROPIES Correlation with the VC-V catalog Publication of the correlation of the 27 highest energy events (2007) the sky is anisotropic at 99% c.l. Publication ICRC 2011 : 33% (21% from isotropy) Without comparison with catalog development of methods able to detect the intrinsic anisotropy of a catalog required to be efficient at low statistics Min(Pvalue) is @ 52 EeV 7
ANISOTROPIES neutron sources (while p iso. by B), @ 1 EeV : neutron travel 9.2 kpc Blind search on the whole sky Target search in the direction of bright Galactic -ray src (HESS/Fermi) no detection upper limits Equatorial dipole d 1-1 -2 no strong large scale anisotropies KASCADE Grande AGASA Auger C-G XGal Gal Phase [ ] 180 90 0 270 Galactic Anti-center Galactic Center 12h 18h 0h 6h -3-4 EAS-TOP 14 A S 15 16 17 18 19 Energy [ev] 20 8 East/West analysis Rayleigh analysis 180 0.2 1 2 3 4 5 20 indication of a smooth transition ~ 2 EeV E [EeV] 12h
CHEMICAL COMPOSITION ] 2 <X max > [g/cm 850 800 EPOSv1.99 QGSJET01 SIBYLL2.1 QGSJETII ICRC 2011 p Most straightforward observable to infer composition 750 700 998 781 619 457 331 143 230 188 1407 1251 186 6 47 Fe mean shower depth maximum : Xmax 650 Direct measurements with FD : ] 18 19 E [ev] Xmax RMS(Xmax) 2 ) [g/cm 70 60 ICRC 2011 p Comparison with MC simulations Measurement of the p/air cross-section Other observables : Muon production depth (SD)... max RMS(X 50 40 30 20 1407 1251 998 781 619 457 331 230 188 143 186 6 47 Fe 9 0 18 19 E [ev]
NEUTRINO FLUX 3 sketches of neutrino detection are possible in Auger Inclined showers ICRC 2011 2 kinds of events can be detected «down-going» : all flavours «up-going» : No detection upper limits Comparison with models Production by the interaction of CRs (GZK processes) Transition models
PHOTON FLUX Possible candidates for the UHECRs ICRC 2011 Top down models Explanation to trans-gzk CRs Decay of SHDM, Monopoles, Z-burst... Photon fraction % Bottom up models Production by the interaction of CRs (GZK processes) Photon fraction 0.1-1% Predictions strongly model-dependent Search in the hybrid data set for No detection upper limits Large Xmax Muon-poor EAS Update soon : stay tuned 11
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BACK UP 13
NEUTRON SOURCE UPPER LIMIT Similar values for 14
PHASE VS AMPLITUDE In case of a real underlying anisotropy a consistency of the phase measurement in ordered energy intervals is expected with lower statistics than that required for the amplitude to significantly stand out of the background noise* *see J. Linsley, Phys. Rev. Lett.,1975, 34 Power [in %] 0 80 60 40 Test on phases Test on amplitudes Likelihood test in adjacent energy bins 20 MC with : - 30,000 evts in each bin - s = 1% 0 3 4 5 6 7 8 9 N bins Phase is ~ 2.5 times more sensitive than the amplitude Auger Data Posterior probability (log-likelihood) : Prescription Pch ~ -3 15
PHOTONS VS NUCLEI Below 15 ev, difficult to distinguish γ/p E > 15 ev, Xmax (γ) > Xmax (p) 16
MODEL DEP. FOR GZK PHOTONS 17
THE COSMIC RAY SPECTRUM The flux constrains detection method detection of extensive air showers above 0 TeV 3 most important detection techniques Cherenkov Fluorescence Surface detectors AUGER 18