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Results on Ultra-High Energy Cosmic Rays from the Pierre Auger Observatory. Valerio Verzi INFN Roma Tor Vergata for the Pierre Auger Collaboration. COSMIC RAYS SPECTRUM (2008). l. Flux x E 2.5. UHECR. ~ 10 20 eV. 1 particle/km 2 /century!. WHERE DO COME FROM?. B. R.

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Valerio Verzi INFN Roma Tor Vergata for the Pierre Auger Collaboration


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    1. Results on Ultra-High Energy Cosmic Rays from the Pierre Auger Observatory Valerio Verzi INFN Roma Tor Vergata for the Pierre Auger Collaboration

    2. COSMIC RAYS SPECTRUM (2008) l Flux x E2.5 UHECR ~ 1020 eV 1 particle/km2/century!

    3. WHERE DO COME FROM? B R E only few candidates Centaurus A B AGN at only 3.4 Mpc • AGN Trajectory in galactic and inter-galactic B 1020 eV 1018 eV Hillas diagram R more details in G.Farrar’s talk Back to origin!

    4. Greisen-Zatsepin-Kusmin (GZK) pgCMB→ N p D+ Interaction with CMB Modification of the spectrum l=5÷10 Mpc GZK cutoff UHECR sources must be closer than 50-100 Mpc!

    5. ATMOSPHERIC SHOWERS 10 li 30 X0 at ground millions of particles … detectors in coincidence

    6. AUGER – HYBRID DETECTOR • Fluorescence Detector (FD): • fluorescence light from the N2 de-excitation • (+) Longitudinal shower development • calorimetric measurement of E • sensitivity to CR mass (Xmax) • (-) Duty cicle ~ 10% FD • Surface Detector (SD): • detection of the shower front at ground • (+) Duty cicle ~ 100% (important for UHECR) • (-) Shower size at ground  E (systematics) • calibration from FD SD

    7. PIERRE AUGER OBSERVATORY Malargue - Argentina SD 1600 water Cherenkov detec. on a 1.5 km hexagonal grid 3000 km2 FD 4 x 6 fluorescence telescopes 50 km

    8. PIERRE AUGER OBSERVATORY Malargue - Argentina SD 1600 water Cherenkov detec. on a 1.5 km hexagonal grid 3000 km2 Installation completed this year FD 4 x 6 fluorescence telescopes 50 km

    9. SD TANKS 1.5 km

    10. FLUORESCENCE TELESCOPE

    11. three 9” PMTs WATER TANK Communicationantenna GPSantenna Electronics enclosure 40 MHz FADC, local triggers, 10 Watts Solar Panel Plastic tank with 12 tons of water Battery box

    12. TANK SIGNAL  m PMT m diffusive Tyvek • m-response ~ track • e/g-response ~ energy 1.2 m ~ 3 Xo Cerenkov light water ‘young’ shower strong e.m. component ‘old’ shower m signal dominates

    13. SD SHOWER RECONSTRUCTION shower front 1.5 km Shower front from particle arrival times Core position and S(1000) from LDF (NGK) fit Signal (VEM) Distance from the core (m)

    14. SD SHOWER RECONSTRUCTION shower front 1.5 km Shower front from particle arrival times Core position and S(1000) from LDF (NGK) fit Signal (VEM) Shower axis resolution Distance from the core (m) E > 1019 eV ~ 10 zenit (degrees)

    15. SD SHOWER RECONSTRUCTION shower front 1.5 km Shower front from particle arrival times Core position and S(1000) from LDF (NGK) fit Signal (VEM) S(1000) ~ E Distance from the core (m) FD calorimetric measurement No simulations!

    16. FD TELESCOPE • Spherical mirror 3.4m radius of curvature Schmidt optics

    17. FD TELESCOPE • 2.2 m diameter diaphragm corrector ring, UV optical filter Schmidt optics

    18. FD TELESCOPE • Camera (focal surface) - 440 PMT’s 30ox30oFOV pixel = 1.5o spot: 15 mm (0.5o) Schmidt optics

    19. FD EVENT bin=100 ns

    20. FD ENERGY SCALE dE dX Energy deposit Nγ Airfly spectrum Fluorescence yield from laboratory measurements 5 photons/MeV at 337 nm Shower energy uncertainty ~ 15%

    21. FD ENERGY SCALE Atmospheric transmission Nγ Nγ at diaphragm Atmospheric monitoring aerosols, clouds, density profiles (Lidar, Central Laser Facility, Ballons, …) Shower energy uncertainty ~ 5%

    22. FD ENERGY SCALE Nγ PMT’s signal at diaphragm Nγ Drum absolute calibration uniform camera illumination with a calibrated light source ~ 5 g/ADC Shower energy uncertainty ~ 10%

    23. FD ENERGY SCALE E Ecal dE dX E ~ 3.5 1019 eV Expected profile: fitted Gaisser-Hillas function Xmax~ 810 g/cm2 Ecal Xmax X Ecal E only a 10% model dependent correction Shower energy uncertainty ~ 4% Log E

    24. SD CALIBRATION USING FD ENERGY S(1000) HYBRID SHOWERS S(1000,q=380) with CIC LINEAR FIT 50 VEM ~ 1019 eV 661 events Statistical uncertainty 7% at 1019 eV 15% at 1020eV PRL 101, 061101 (2008) FD syst. uncertainty (22%) dominates

    25. AUGER SCIENCE SPECTRUM COMPOSITION SOURCES

    26. ENERGY SPECTRUM - q<600 Data up to 31/08/07 Aperture 7000 km2 sr yr ~ 1 year Auger completed 2 x HIRES 4 x AGASA PRL 101, 061101 (2008) Full efficiency above 1018.5 eV  3% uncertainty on aperture

    27. ENERGY SPECTRUM - q<600 Data up to 31/08/07 Exp. Observed > 4x1019 167±3 66 > 1020 35±1 1 Aperture 7000 km2 sr yr ~ 1 year Auger completed 2 x HIRES 4 x AGASA PRL 101, 061101 (2008) Full efficiency above 1018.5 eV  3% uncertainty on aperture Evidence of GZK cutoff

    28. ENERGY SPECTRUM - q<600 Fit E-γ HiRes: 5.1 ± 0.7 γ = 4.2 ± 0.4 γ = 2.69 ± 0.06 difference with respect to reference shape Js = A x E-2.69 GZK cut off

    29. ENERGY SPECTRUM Comparison of the three Auger spectra - consistency Different reconstruction 0-60 degrees 60-80 degrees Exposure from simulation Ankle ICRC 07

    30. Auger combined compared to Hires and Agasa Fairly agreement within systematic uncertainties ICRC 07

    31. AUGER SCIENCE SPECTRUM COMPOSITION SOURCES

    32. ELONGATION RATE (< A> ~ 5) Change of slope correlation with ankle ? preliminary Systematics < 15 g /cm2 Not proton dominated composition at the highest energies

    33. SENSITIVITY TO PHOTON SHOWERS g A Fluorescence Detector Xmax from shower longitudinal profile. (SD) Shower front curvature Surface Detector Shape of the front of the shower (SD) Shower front thickness A g

    34. PHOTON FRACTION LIMIT preliminary ~ 3 % Top Down models: Super Heavy Dark Matter Relic of “topological defects” HP: Haverah Park A1,A2: AGASA Y: Yakutsk Astro. Ph. 29 (2008), 243. Astro. Ph. 27 (2007), 155.

    35. NEUTRINO FLUX LIMIT Signature: very inclined showers with high e.m. signal component hadronic showers: signal dominated by muon component 87 degrees PRL 100 (2008),211101.

    36. AUGER SCIENCE SPECTRUM COMPOSITION SOURCES

    37. GALACTIC CENTER ANISOTROPIES H.E.S.S.: TeV g-ray from Sagittarius A* Excess in previous experiments GC AGASA 2.5s SUGAR 2.9s • larger exposure • GC lies well in the f.o.v. Auger: No statistically significant excess in Auger data • angular windows: • AGASA and SUGAR • 10° and 20° around the GC (charged CR’s) • 1° around the GC • 0.1 < E < 1 EeV (photons) • 1 < E < 10 EeV (neutrons)

    38. EVIDENCE OF ANISOTROPY Correlation of the Highest-Energy (>5.7x1019 eV) Cosmic Rays with Nearby (<75 Mpc) Extragalactic Objects Centaurus A Science 318 (2007), 939. Astro. Ph. 29 (2008), 188.

    39. EVIDENCE OF ANISOTROPY Véron &Véron-Cetty catalogue 442 AGN (292 in f.o.v.) z<0.017 (71 Mpc) 27 events E > 57 EeV 3.20 radius galactic coordinates Doublet from Centaurus A Border of the f.o.v. Relative exposure Super-galactic plane

    40. ANALYSIS METHOD Source y Probability p that one event from isotropic flux is close (<y) to at least one source p = fraction of “Auger sky” covered by windows y centred on sources CR Fix candidate sources and maximum angular distance y Prob. >k of the N events from isotropic flux correlate by chance with sources (<y)

    41. ANALYSIS METHOD Source y Probability p that one event from isotropic flux is close (<y) to at least one source p = fraction of “Auger sky” covered by windows y centred on sources Three parameter scan to find the maximum anisotropy (minimum of P) 1- Minimum CR energy (->N) minimize deflections in B 2- Maximum source distance zmax GZK 3- Maximum angular separation y deflections in B and angular resolution CR Fix candidate sources and maximum angular distance y Prob. >k of the N events from isotropic flux correlate by chance with sources (<y)

    42. RESULTS Absolute minimum y = 3.20 zmax = 0.017 (71 Mpc) E > 57 EeV 1.2 year full Auger Isotropy hypothesis rejected with at least 99% confidence level exploratory scan (01/01/04- 27/05/06) confirmation on an independent data set (27/05/06- 31/08/07)

    43. WHAT ABOUT NOT CORRELATED EVENTS? CR closest AGN Events with low galactic latitudes |b| < 120 Isotropic flux • catalogue • incompleteness • larger deflections • in galactic • magnetic field 6 events less with 5 not correlated

    44. THE ANGULAR SEPARATION Y • angular resolution ~ 10 < y (=3.20) • y determined by galactic and inter-galactic magnetic fields Simulation including galactic magnetic field simulated protons (isotropy) 27 observed events y=3.20

    45. THE ANGULAR SEPARATION Y deflection • angular resolution ~ 10 < y (=3.20) • y determined by galactic and inter-galactic magnetic fields Simulation including galactic magnetic field simulated protons (isotropy) 27 observed events y=3.20 correlated events are likely protons but elongation rate suggests a mixed composition at the highest energies …

    46. CONNECTION TO THE GZK CUT OFF events E > 5.7 1019 eV spectrum sources < 71 Mpc flux reduced by 50% but …

    47. CONNECTION TO THE GZK CUT OFF events E > 5.7 1019 eV spectrum sources < 71 Mpc flux reduced by 50% but … GZK Horizon is ~200 Mpc maximum distance of the sources from which 90 % of the protons arrive on Earth with energy above a given value. 90%

    48. CONNECTION TO THE GZK CUT OFF events E > 5.7 1019 eV spectrum sources < 71 Mpc flux reduced by 50% but … GZK Horizon is ~200 Mpc maximum distance of the sources from which 90 % of the protons arrive on Earth with energy above a given value. 90% For an +30% energy estimator the Horizon would be ~100 Mpc

    49. CONNECTION TO THE GZK CUT OFF events E > 5.7 1019 eV spectrum sources < 71 Mpc flux reduced by 50% but … GZK Horizon is ~200 Mpc maximum distance of the sources from which 90 % of the protons arrive on Earth with energy above a given value. 90% For an +30% energy estimator the Horizon would be ~100 Mpc Uncertainty on energy scale ~ 25%

    50. CONCLUSIONS • Auger is fully operational: exposure ~ 1 year of Auger completed • UHECR anisotropy angular distribution similar to that of AGN within ~ 70 Mpcsources are of extra-galactic origin primaries are likely protons which interact with CMB radiation (GZK)