for the Pierre Auger Collaboration 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 E2.5 UHECR ~ 1020 eV 1 particle/km2/century!

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

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

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

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

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

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

SD TANKS 1.5 km

FLUORESCENCE TELESCOPE

WATER TANK Communication antenna GPS antenna Electronics enclosure 40 MHz FADC, local triggers, 10 Watts Solar Panel three 9” PMTs Plastic tank with 12 tons of water Battery box

TANK SIGNAL  m-response ~ track e/g-response ~ energy ‘young’ shower 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

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

SD SHOWER RECONSTRUCTION 1.5 km shower front 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)

SD SHOWER RECONSTRUCTION 1.5 km shower front 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!

FD TELESCOPE Spherical mirror 3.4m radius of curvature Schmidt optics

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

FD TELESCOPE Camera (focal surface) - 440 PMT’s 30ox30o FOV pixel = 1.5o spot: 15 mm (0.5o) Schmidt optics

FD EVENT bin=100 ns

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

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

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

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

SD CALIBRATION USING FD ENERGY 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

AUGER SCIENCE SPECTRUM COMPOSITION SOURCES

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

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

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

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

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

AUGER SCIENCE SPECTRUM COMPOSITION SOURCES

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

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

PHOTON FRACTION LIMIT ~ 3 % preliminary HP: Haverah Park A1,A2: AGASA 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.

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

AUGER SCIENCE SPECTRUM COMPOSITION SOURCES

GALACTIC CENTER ANISOTROPIES H.E.S.S.: TeV g-ray from Sagittarius A* Excess in previous experiments GC AGASA 2.5s SUGAR 2.9s Auger: larger exposure GC lies well in the f.o.v. 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)

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.

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

ANALYSIS METHOD Fix candidate sources and maximum angular distance y CR Source y Fix candidate sources and maximum angular distance 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 Prob. >k of the N events from isotropic flux correlate by chance with sources (<y)

ANALYSIS METHOD Fix candidate sources and maximum angular distance y CR Source y Fix candidate sources and maximum angular distance 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 Prob. >k of the N events from isotropic flux correlate by chance with sources (<y) 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

RESULTS Absolute minimum y = 3.20 zmax = 0.017 (71 Mpc) E > 57 EeV Selected events Events correlated Expected for isotropy 27 20 5.6 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)

WHAT ABOUT NOT CORRELATED EVENTS? Events with low galactic latitudes |b| < 120 Isotropic flux catalogue incompleteness larger deflections in galactic magnetic field CR closest AGN Selected events Events correlated Expected for isotropy Full data sample 27 20 5.6 |b| > 120 21 19 5.0 6 events less with 5 not correlated

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

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 deflection correlated events are likely protons but elongation rate suggests a mixed composition at the highest energies …

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

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%

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

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%

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

CONCLUSIONS Auger is fully operational: exposure ~ 1 year of Auger completed UHECR anisotropy angular distribution similar to that of AGN within ~ 70 Mpc sources are of extra-galactic origin primaries are likely protons which interact with CMB radiation (GZK) evidence of GZK cut-off in the spectrum confirming HIRES data no photon and neutrino candidates (disfavour TOP-DOWN models)

CONCLUSIONS Auger is fully operational: exposure ~ 1 year of Auger completed UHECR anisotropy angular distribution similar to that of AGN within ~ 70 Mpc sources are of extra-galactic origin primaries are likely protons which interact with CMB radiation (GZK) evidence of GZK cut-off in the spectrum confirming HIRES data no photon and neutrino candidates (disfavour TOP-DOWN models) but … Xmax studies disfavour a proton dominated composition at the highest energies Consistency or not with the GZK horizon? Two events from CenA, none from Virgo. Why? Need more statistics (~ 70 events/year above 4x1019 eV) and better control of systematics

FUTURE DEVELOPMENT Auger North (Colorado, US) Full sky coverage (talk of prof. J.Bluemer) Full sky coverage Array: 8000 square miles ≈ 20000 km2 ≈ 7 x Auger South) events above 4x1019 eV (GZK cutoff) Auger South: ~ 70 events/year Auger North: ~ 500 events/year

BACK UP SLIDES

TANK CALIBRATION Online calibration with background muons (2 kHz) Vertical m PMT m diffusive Tyvek Online calibration with background muons (2 kHz) 1.2 m ~ 3 Xo Cerenkov light water muon peak VEM peak scintillator 1 VEM ≈ 100 p.e.

TIME RESOLUTION Doublets Dia Noche 11m Doublets Low energy events (~ 1017 eV) used to compare the time measurement of each tank GPS intrinsic time resolution 8 ns Time precision of each individual tank ~ 12 ns

SD-TANK TRIGGER SD-EVENT TRIGGER Threshold Trigger ~ 20 Hz Time Over Threshold Trigger ~ Hz 5 s SD-EVENT TRIGGER hottest tank surrounded by 6 working stations

SD SHOWER RECONSTRUCTION distance from the core size parameter Lateral distribution function (LDF) NGK slope parameter (β(q)= 2-2.5) S(1000) and the core position from the fit core Signal (VEM) S(1000) 34 tanks distance from the core (m)

SD CALIBRATION USING FD ENERGY vertical shower inclined shower for the same energy and mass S(1000;0)> S(1000;q) Xg Xg/cosq Attenuation curve derived with constant intensity cut technique ground for each shower determine the signal that would have had at 380 S38 = S(1000,380)

SD CALIBRATION USING FD ENERGY LINEAR FIT 19% measurement of the energy resolution 16%-S38 8%-EFD PRL 101, 061101 (2008)

SD APERTURE Aperture 7000 km2 sr yr (3% error) Full efficiency above 3x1018 eV ~20.000 events above 3 1018 eV Aperture 7000 km2 sr yr (3% error)

ELONGATION RATE

Comparison with PAO data, without and with acceptance

ELONGATION RATE

ELONGATION RATE p - EPOS Fe - EPOS Fe - QGSJETII p - QGSJETII proton iron The mass spectrum is not proton dominated at the highest energies Ambiguous interpretation: uncertainties of hadronic interactions at highest energies

GALACTIC CENTER ANISOTROPIES Angular window Windows centred in the GC: Nobs/Nexp Ratio (err.: stat, syst) search for photons 1.30 (G) 192.1 / 191.2 1.00 ± 0.07 ± 0.01 100 5663 / 5657 1.00 ± 0.02 ± 0.01 200 22274 / 22440 0.99 ± 0.01 ± 0.01 0.80 (G) 16.9 / 17.0 0.99 ± 0.17 ± 0.01 1463 / 1365 1.07 ± 0.04 ± 0.01 5559 / 5407 1.03 ± 0.02 ± 0.01 GC lies well in the Auger f.o.v. 0.1 < E < 1 EeV search for neutrons 1 < E < 10 EeV

ANISOTROPY 15 12 3.2 13 8 2.7 27 20 5.6 21 19 5.0 Events Expected for correlated Expected for isotropy Exploratory scan 1 Jan 04- 27 May 06 zmax = 0.018 E > 56 EeV y = 3.10 15 12 3.2 Test on an independent data set 27 May 06- 31 Aug 07 ** running prescription 13 8 2.7 Full data set 1.2 year full Auger * zmax = 0.017 (71 Mpc) E > 57 EeV y = 3.20 27 20 5.6 Full data set excluding region of the galactic plane (|b| > 120) 21 19 5.0 *Probability to see such anisotropy with an isotropic flux = 10-5 5 of the 7 events not correlated are close to the galactic plane ** 1.7 10-3

Red dots: 13 HiRes events (claim consistent with isotropy) Black dots: 27 Auger events

GZK and mass composition Only protons and not too light nuclei are able to reach the Earth for energies above ~ 60 EeV