Stefano Argirò 1 for the Auger Collaboration 1 University of Torino, Italy, and INFN Physics case The Auger Observatory Performance Preliminary Analysis Conclusions EPS 2003 Status, Performance and Perspectives of the Auger Observatory

Air Showers generated by primaries with E>10 20 eV exist  20 events observed in the past 40 yr Standard Astrophysical models cannot easily account for such E Astrophysical sources must be near GZK cutoff at  50 Mpc for E>10 20 eV Near sources should be identified by point source astronomy High magnetic rigidity of the primaries Stefano Argirò, “Status... of the Pierre Auger Observatory” Physics Case

What is the source of CR of such energies ? Are sources uniformly distributed ? What is the composition of the primaries ? Is GZK violated ? The experimental situation is rather controversial: The Pierre Auger Observatory responds with: Difficulty of the measurements Low statistics Precision Measurements Hybrid Detector Large area km 2 Full sky coverage (Harmonic Analysis) Sensitivity to -induced showers ! 1 particle/yr/km 2 E> particle/yr/km 2 E>10 20 Stefano Argirò, “Status... of the Pierre Auger Observatory” The UHECR Problem

Physics (oversimplified) scenarios Anisotropy – point sourcesAstroph objects Isotropydecay of superheavy relics or other new physics Uniformly distributed Astroph sources but depending on composition & magnetic fields Composition: gamma new physics heavy NS, very near sources GZK Violated Conserved near Astroph sources new physics far Astroph sources Distribution of arrival directions proton goto GZK features of the spectrum Experimental evidenceMeaning

Integrated exposure No. of Events (E > eV ) 1, Year Integrated Aperture (km^2* str *year) Fly’sEye AGASA HiRes Auger (N+S) EUSO Stefano Argirò, “Status... of the Pierre Auger Observatory”

Northern site Millard County Utah, USA Stefano Argirò, “Status... of the Pierre Auger Observatory” Auger Sites

1600 Water Cerenkov Detectors, 1.5 km spacing 24 Fluorescence Telescopes + extensive atmospheric monitoring 3000 km 2 of instrumented area Southern Site Northern Site: configuration to be detailed Malargue Population : Lat : -35, Long: -69, Elevation: 1430 m Stefano Argirò, “Status... of the Pierre Auger Observatory” The Pierre Auger Observatory

PreProduction Array Engineering Array

Surface Array Simple and reliable detectors 100% duty cycle Energy Determination relies on simulation Fluorescence Detector Quasi calorimetric energy measurement Tracks directly shower developement % duty cycle Sistematics from atmospheric transparency Combination Cross Calibration Better control of systematics Superior Angular resolution Independent measurement of Energy Composition:   /  e, X max Stefano Argirò, “Status... of the Pierre Auger Observatory” The Hybrid Detector Concept

Solar panel Comm antenna GPS antenna Three 8” PM Tubes Plastic tank 12 m 3 of de-ionized water White light diffusing liner Stefano Argirò, “Status... of the Pierre Auger Observatory” electronic box 40 Mhz sampling bit FADC Local Trigger The Surface Detector

SD Calibration Detect presence of hump from atmospheric muons with a special trigger. Scale to Vertical Equivalent Muon measured on a sample tank equipped with scintillators Stefano Argirò, “Status... of the Pierre Auger Observatory”

30° x 30 ° fov Schmidt optics 440 pixels 1.5 ° Ø pixel 12 bit FADC 10 Mhz f s < 4 g/cm 2 Digital trigger Fluorescence Detector Stefano Argirò, “Status... of the Pierre Auger Observatory”

Aperture

Mirror

Stefano Argirò, “Status... of the Pierre Auger Observatory”

FD Calibration Absolute: End to End Calibration The Drum device installed at the aperture uniformly illuminates the camera with light from a calibrated source (1/month) Alternative techniques for cross checks Scattered light from laser beam Statistical Relative: UV LED + optical fibers (1/night) Stefano Argirò, “Status... of the Pierre Auger Observatory” All agreed within 10% for the EA N Photons at diaphragm  FADC counts Mirror Camera Calibrated light source Diffusely reflective drum

Atmospheric Monitoring Crucial for an accurate energy measurement Wheather stations Horizontal Attenuation Monitors Aerosol Phase Function Monitors Cloud Monitors Balloon launches Lidar systems Stefano Argirò, “Status... of the Pierre Auger Observatory” Rayleigh (molecular) scattering and Mie (aerosol) scattering are the physical process to be accounted for. Rayleigh is easy to measure, but Mie is not.

Status Engineering Array Phase completed 35 Surface Detector Tanks 2 Fluorescence Telescopes Production phase started 100 tanks positioned with production electronics 200 by end of September 400 by Jan by Jul telescopes commissioned with production electronics 3+2 by end 2003(stereo detection by end of 2003) 6+6 by first quarter eye buildings completed Successful Detection of Hybrid events Stefano Argirò, “Status... of the Pierre Auger Observatory”

Performance SD :  6000 triggers since Dec 2001  600 shower candidates E>10 18  120 with more than 5 tanks FD:  1000 triggers  500 real showers  50 have quality such that energy can be roughly estimated many laser shots for detector studies 77 hybrid events Stefano Argirò, “Status... of the Pierre Auger Observatory”

Geometrical Reconstruction SD Stefano Argirò, “Status... of the Pierre Auger Observatory”  core  100m  ,   1  x core, y core from barycenter of triggered tanks weighted by signal ,  from minimization of ,  from arrival times

Shower front Shower core hard muons EM shower Stefano Argirò, “Status... of the Pierre Auger Observatory”

FD Geometrical Reconstruction SDP Shower Axis hit station t SD Shower Front RpRp t0t0 impact point ii 00 FD Two Steps: Shower Detector Plane Axis SDP The Plane that minimizes the sum of the square angular differences from the direction of the hit pixels  Nsdp  0.3  Stefano Argirò, “Status... of the Pierre Auger Observatory”

FD Mono: Axis  core  800m  ,   1  Tests with laser shots thrown at known direction (aiming at a star) The Time Fit FD stereo: intersection of SDP

Hybrid Reconstruction Problem of the time fit: 3 parameter fit from an almost linear function between time and position accuracy depends on geometry (toward/outward) Additional constraint from time of stations  core  30 m  ,   0.3  Hybrid resolution Stefano Argirò, “Status... of the Pierre Auger Observatory”

Analysis Example  = 54.3 ± 0.5   = ± 0.8 n = 11 E =20  35 EeV #184599,Friday April Stefano Argirò, “Status... of the Pierre Auger Observatory”

Lateral Distribution Stefano Argirò, “Status... of the Pierre Auger Observatory” Energy from S1000  10 events/curve

Signal Fluctuations Stefano Argirò, “Status... of the Pierre Auger Observatory”

Longitudinal Profile Received light at aperture, emitted between X and X+  X: Atmospheric Transmission T rayleigh  T aerosol Fluorescence yield function F y from lab measurements Cerenkov contamination subtracted by an iterative procedure e-m energy estimation: From Gaisser-Hillas fit to profile Stefano Argirò, “Status... of the Pierre Auger Observatory”

run 505 ev 544 theta 55.6 ° phi ° X 9.8 Km Y 8.8 Km R 13.1 km Eem  eV Stefano Argirò, “Status... of the Pierre Auger Observatory”

FD Event Display Stefano Argirò, “Status... of the Pierre Auger Observatory”

run 531 ev 68 theta 48.1° phi ° X 4.4 Km Y 19.0 Km R 19.5 km Eem  eV Stefano Argirò, “Status... of the Pierre Auger Observatory”

Conclusions Stefano Argirò, “Status... of the Pierre Auger Observatory” The Engineering Array proved that: The Detector design is sound The technical difficulties are sorted out We are able to calibrate and operate the detectors smoothly We are able to take consistent data and perform a thorough and consistent analysis The Challenge: Timely completion of the Southern Observatory Startup of Northern Observatory

TevatronLHC

D. Bergman, ICHEP 2002 Stefano Argirò, “Status... of the Pierre Auger Observatory”