Jim Matthews Louisiana State University Results from the Pierre Auger Observatory ECRS, Moscow, 4 July

~ E -2.7 ~ E -3.1 Above eV (50 Joules!): Φ ≈ 1 per km 2 per century Very low flux … Very big detectors 2

Argentina Australia Bolivia * Brasil Croatia Czech Republic France Germany Holland Italy Poland Mexico Netherlands Portugal Romania Slovenia Spain United Kingdom USA Vietnam * ~ 500 Scientists 17 Countries 3

Aims of the experiment Measure the energy spectrum of high energy cosmic rays up to and beyond energies of eV Determine the sources of these cosmic rays Determine the elemental composition of cosmic rays Study extensive air showers -> particle interactions 4

How to get particles to extreme energy Fermi Acceleration (Bottom-Up) - repeated encounters with strong plasma shocks - naturally produces power-law with correct index - maximum energy can be extremely large - observed in nature “Exotic” (Top-Down) - decay of massive relic particles - interaction of nu’s w/cosmic background neutrinos (-> Z) - topological defects, other things ? - Signature: protons, photons, neutrinos 5

“GZK” First pointed out in 1966 in two papers, one by Greisen and one by Zatsepin & Kuz’min p +  (2.7 o K)    p +  6 Nuclei photo-disintegrate at similar thresholds, distances

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Surface Arrays and Fluorescence Detection - Arrays: 24/7 operation, very large size (statistics) - Fluorescence: ‘calorimetry’ = good energy resolution (spectrum) 8

38° South, Argentina, Mendoza, Malargue 9

Surface Array 1650 detector stations 1.5 Km spacing 3000 km 2 Fluorescence Detectors 4 Telescope enclosures 6 Telescopes per enclosure 24 Telescopes total Design: AGASA spectrum > 100 events/yr above eV 10

View of Los Leones Fluorescence Site 11

The Fluorescence Detector 3.4 m spherical mirror PMT camera Spherical surface camera 440 PMT with light collectors Large 30 0 x30 0 field of view 1.5º pixel fov (spot 1/3 of pixel) FADC trace 100  s 12

Energy reconstructed from measured maximum size --- calorimetric (minimal MC) 13

Reconstructed longitudinal profiles 14

15 μ e

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θ~ 48º, ~ 70 EeV (7 x eV) Lateral density distribution 18 detectors triggered km 18

SD Energy Calibration The power of hybrid….. Does NOT rely on shower simulation FD SD E SD = A (S 38 ) b b ~ 1 SD Energy resolution better than 20% 19

20 Includes hybrid data (See Settimo & Auger Collab, EPJ (2012))

21 “Infill”

22 Here: from 2011 ICRC

Inferring the Primary Mass Variation of Depth of Shower Maximum with Energy ************************ X max log E p Fe 23 X max correlates tightly with the depth of 1 st interaction

Nuclear Composition: Shower Depths of Maximum X max These suggest high cross section and high multiplicity at high energy. Heavy nuclei? Or protons interacting differently than expected? (See Nellen presentation, this meeting) Statistics lacking for the (anisotropic) trans-GZK energy regime! (Crucial for calculation of the diffuse cosmogenic neutrino flux) Anisotropy 24 Physical Review Letters 104 (2010)

25 SD: Development of Muons in Shower SD: Asymmetry of Shower front thickness FD: Mean depth of Shower Max FD: Fluctuations of Shower Max Spectral “Ankle”

26 Presentation by Nellen: Data show more muons than simulations

27 “Tail” dominated by protons Proton-Air Cross Section from the Depth of Shower Maximum

28 To appear in Phys. Rev. Lett. 2012

29 To appear in Phys. Rev. Lett. 2012

30 See presentation of Navarro at this meeting … Photon limits

31 See presentation of Navarro at this meeting …

Summary Energy spectrum exhibits ankle and GZK suppression The sources are extragalactic, within the “GZK sphere”: (weak) anisotropy persists above ~60 EeV The composition is baryonic, appearing to become iron-dominated (or new particle physics … models do not give enough muons) p-Air, p-p cross sections beyond the LHC energy Few/no photons or neutrinos (disfavors exotic “top down” models) Photons/neutrinos nearing GZK regime 32

33 What’s Next? Auger has been “operating” since 2004, fully deployed since The international agreement runs for 3.5 more years (end of 2015) We hope to continue after that, are exploring new technologies in use now or can be started very soon … -- Auger Engineering Radio Array - AERA - see presentation by Fraenkel -- Microwave, GHz,... prototypes operating -- Focus on better composition determination through new muon detectors, new flourescence techniques, … R&D спасибо