The Pierre Auger Observatory Results on the highest energies

1. The Pierre Auger ObservatoryResults on the highest energies Ruben Conceição for the Pierre Auger Collaboration TAM, Venice, March 7th 2013

2. Ultra High Energy Cosmic Rays Cosmic ray spectrum R. Conceição

3. Ultra High Energy Cosmic Rays Cosmic ray spectrum ? Tevatron (p-p) LHC (p-p) R. Conceição

4. Ultra High Energy Cosmic Rays Cosmic ray spectrum • UHECRs • Where/how are they produced? • What is the flux composition? • How do they interact? • Study Hadronic interactions at sqrt(s) ~ 100 TeV ? Tevatron (p-p) LHC (p-p) R. Conceição

5. Pierre Auger Observatory • Locatedinthe Pampa Amarilla, Mendoza, Argentina • Altitude: 1400 m a.s.l. ~ 60 km R. Conceição

6. Pierre Auger Observatory Low energy extension • Aim to E ≈ 1017eV • AMIGA • Denser array plus muon detectors • HEAT • 3 additional FD telescopes with a high elevation FoV • ~ 1600 Surface Detector (SD) Stations • 1.5 km spacing • 3000 km2 Data taking since 2004 Installation completed in 2008 ~ 60 km • 4 Fluorescence Detectors (FD) • 6 x 4 FluorescenceTelescopes

7. Surface Detector Station • Water Cherenkov Tank • Measure charged particles at ground • 100% Duty cycle • SD station • Plastic Tank • Reflective tyvek liner • 12 m3 purified water • 3 PMTs (9 inches) PMT µ e R. Conceição

8. Fluorescence Detector • Operates in moonless nights • Duty cycle ~13% • Collects the fluorescence photons to reconstruct the energy deposit longitudinal profile • 6 Telescopes each with 30° x 30° FoV • Camera composed by 440 PMTs Need to monitor the atmosphere… R. Conceição

9. Atmospheric monitoring Opportunity to study the atmosphere! R. Conceição

10. Event Reconstruction Surface Detector Fluorescence Detector Longitudinal Profile Evolution seen in camera gives the shower geometry Energy is calculated by integrating the longitudinal profile (calorimetric measurement) • Lateral Distribution (LDF) • Tank hit time gives shower direction • Energy is obtained using the signal measured at 1000 meters from the shower core S(1000) Xmax R. Conceição

11. Event Reconstruction Surface Detector Fluorescence Detector Longitudinal Profile Evolution seen in camera gives the shower geometry Energy is calculated by integrating the longitudinal profile (calorimetric measurement)  Increase accuracy on the energy and direction measurements • Lateral Distribution (LDF) • Tank hit time gives shower direction • Energy is obtained using the signal measured at 1000 meters from the shower core S(1000) Xmax  Allow complementary shower description R. Conceição

12. Energy Calibration of the SD R. Pesce, ICRC2011 S38 is the equivalent signal of S(1000) of a shower with θ= 38o Calibration Systematic Uncertainties: - 7% at 1019eV - 15% at 1020eV SD • FD Energy Systematics: • Fluorescence yield 14% • FD abs calib 9.5% • Invisible Energy 4% • Reconstruction 8% • Atmospheric Effects 8% • TOTAL: 22% FD

13. Energy Spectrum Mass Composition HadronicInteractions Search for photons and neutrinos Results on UHECRs R. Conceição

14. Energy Spectrum Mass Composition HadronicInteractions Search for photons and neutrinos Results on UHECRs R. Conceição

15. Energy spectrum F. Salamida, ICRC2011 • SD has a higher exposure ( ~20905 km2 sryr) allowing to reach higher energies • Energy resolution is around 15% • Unfolding method to correct for bin-to-bin migration • FD (Hybrid) can reach lower energies but exposure is MC based • Good agreement between FD and SD SD R. Conceição

16. Combined Energy Spectrum (FD+SD) R. Conceição

17. Combined Energy Spectrum • Ankleregionclearlyobserved • Veryhighstatistics • Galatic to extragalatictransition? • Astrophysicalinterpretationdepends: • Primarycomposition • Sourcesdistribution • ... R. Conceição

18. Combined Energy Spectrum • Auger data shows a flux suppression at the highest energies • Cutoff significance > 20 σ • This feature is compatible with: • GZK cuttoff • Greisen, Zatsepin, Kuz'min(1966) • Cosmic ray interaction with CMB • Sources running out of power R. Conceição

19. Combined Energy Spectrum • Auger data shows a flux suppression at the highest energies • Cutoff significance > 20 σ • This feature is compatible with: • GZK cuttoff • Greisen, Zatsepin, Kuz'min(1966) • Cosmic ray interaction with CMB • Protons • Photo-pion production • Irons • Photo-dissociation R. Conceição

20. Combined Energy Spectrum D. Allard, 1111.3290 • Auger data shows a flux suppression at the highest energies • Cutoff significance > 20 σ • This feature is compatible with: • GZK cuttoff • Greisen, Zatsepin, Kuz'min(1966) • Cosmic ray interaction with CMB • Sources running out of power R. Conceição

21. Combined Energy Spectrum R. Conceição

22. Energy Spectrum Mass Composition HadronicInteractions Search for photons and neutrinos Results on UHECRs R. Conceição

23. Composition Variables • The moments of the Xmax distribution (mean and RMS) are sensitive to primary composition • As the iron showers spend more energy their mean Xmax and shower to shower flutuations are smaller R. Conceição

24. Analysis procedure • Shower reconstruction accounts for different types of light and propagation • Fluorescence light: isotropic emission • Cherenkov light: beamed emission • Cherenkov scattering • Rayleigh • Mie (aerosols) Early Stage Late Stage R. Conceição

25. Analysis procedure • Apply quality cuts to reconstructed events • Atmospheric monitoring • Good geometrical reconstruction • Xmax in the FoV • … • Apply anti-bias cuts (Xlow ; Xup) • Select geometries that allow to observe the full Xmax distribution • Cuts derived from data • MC based analyses give the same results 1018.1 < E < 1018.2 eV R. Conceição

26. Resolution of the reconstructed Xmax • The detector resolution for Xmax has been estimated from MC simulations to be 20 g cm-2 • StereoEvents (eventsseenby 2 FDs) can beused to check MC performance R. Conceição

27. Moments of the Xmax distribution D. Garcia-Pinto, ICRC2011 Auger • As energy increases data seems to favour a heaviercomposition • Breakoftheelongation rate around log(E/eV) = 18.38 • Theinterpretationintermsofmasscompositiondependsonthehadronicinteractionmodels Tevatron + 0.07 - 0.17 R. Conceição

28. Moments of the Xmax distribution Auger • Same Data (Xmax) • New hadronic interaction models with LHC constraints • Spread between models diminishes • The interpretation depends of hadronic interaction physics at energy above the LHC • E.g.: These results can be mimic with a change in the cross-section without violating the Froissart bound LHC Tevatron R. Conceição

29. Muon Production Depth D. Garcia-Gamez, ICRC2011 • SD Events • Inclined shower events • θ in [55:65] • Mostly Muons • Use arrival time to reconstruct production depth • The maximum of the muon production profile, Xμmax, is sensitive to the primary mass composition • Xμmaxis correlated with Xmax(e.m.) R. Conceição

30. Asymmetry of the Signal Rise Time D. Garcia-Pinto, ICRC2011 • Azimuthal asymmetry in the SD signal is correlated with Xmax • Early vs. late • The angle of maximum asymmetry, Θmax, is sensitive to the primary mass composition • Use the asymmetry of the rise times signal • Statistical method (no event-by-event determination) R. Conceição

31. Meaurements of Shower Development D. Garcia-Pinto, ICRC2011 • SD statistics allow us to reach higher energies • Compatible results within systematic uncertainties • Indication of heavier composition at higher energies? SD SD FD FD R. Conceição

32. Meaurements of Shower Development • SD statistics allow us to reach higher energies • Compatible results within systematic uncertainties • Indication of heavier composition at higher energies? SD SD FD FD R. Conceição

33. Interpreting the data in terms of mass composition evolution Mean RMS ln(A) JCAP 1302 (2013) 026 Fe 4.0 N 2.6 He 0.7 p 0.0 All the models indicate intermediate masses at the highest energies with a small dispersion in ln(A) R. Conceição

34. Energy Spectrum Mass Composition HadronicInteractions Search for photons and neutrinos Results on UHECRs R. Conceição

35. Cross-section measurement • Measurement of the proton-air cross section at sqrt(s)=57 TeV • The exponential tail of the Xmax distribution is sensitive to the primary cross-section • Deepest events are proton dominated • Except for small fraction of photons which can be estimated from data • Apply fiducial cuts to get unbiased tail R. Conceição

36. p-air & p-p cross section at Auger R. Ulrich, ICRC2011 Phys. Rev. Lett. 109, 062002 (2012) Using standard Glauber formalism

37. Muon Measurements Strategies R. Conceição

38. Muon Measurements Strategies • Jump Method • Count Peaks (Muons) • Smoothing Method • Obtain smooth function trace (e.m. signal)

39. Muon Measurements Strategies • Ground signal from inclined showers is muon dominated • Fit footprint at ground using MC prediction

40. Muon Measurements Strategies • Use Hybrid Events • Shower Universality • Sμ( Xmax, S(1000)) • Parameters have some model dependence

41. Muon Measurements Strategies • Use Hybrid Events • Fit longitudinal profile with MC • Compare expected signal at ground

42. Results on the number of muons R. Engel, UHECR2012 Showers up to 60° zenith angle Inclined Shower (Muon dominated) • Models systematically bellow data even for iron primaries • Energy scale uncertainty (22%) • Mixed composition • Hadronic interaction models None of these provide an easy solution by itself R. Conceição

43. Number of muons at E = 10 EeV A. Yushkov, UHECR2012 • Results presented with respect to QGSJet-II proton (E = 1019eV) • Different methods present similar results • Muon signal attenuates faster in simulations than in data • Muon energy spectra? EPOS1.99 Iron Showers R. Conceição

44. Energy Spectrum Mass Composition HadronicInteractions Search for photons and neutrinos Results on UHECRs R. Conceição

45. Measurement of photons and neutrinos FD: search for events with deep Xmax Photons Neutrinos SD: search based on signal time structure Look for almost horizontal showers Experimental signature: “Young showers”, i.e. mostly with e.m. particles R. Conceição

46. Limits on photons and neutrinos Photons Neutrinos M. Settimo, ICRC2011 V. Scherini, UHECR2012 Y.Guardincerri, ICRC2011 Astropart. Phys., 35, 660 (2012) • No neutrino/photon observed yet • Top-down scenarios disfavoured • GZK photons/neutrinos within reach in the next years • Optimistic scenarios (proton primaries) R. Conceição

47. Summary • Spectrum • Ankle clearly observed around (6X 1018eV) • Flux suppression established at (6 X 1019eV) • Composition • Indication of light(heavier) composition at lower(higher) energies • Complex mass composition scenario (interpretation depends of hadronic interactions) • Hadronic Interactions • Proton-Air cross section measured at √s = 57 TeV • Models predict fewer muons than observed • Energy scale, composition, hadronicinteraction models? • Photons and Neutrinos • Observation Limits were set • Top-down models disfavored R. Conceição

48. Future • Accumulate Statistics • Huge observatory running smoothly • Build a consistent picture of the shower • Multivariate Analyses • Independent measurement of the e.m. and muonic shower component at ground • Muon detectors upgrade? R. Conceição

49. end R. Conceição

50. BACKUP R. Conceição