ICHEP `06, Moscow The Auger project – status and results G. Matthiae University and Sezione INFN of Roma “Tor Vergata” Study of the highest energy cosmic rays 17 Countries: Argentina, Bolivia, Australia, Brazil, Rep.Ceca, France, Germany, Italy, Mexico, Netherlands, Poland, Portugal, Slovenia, Spain, UK, USA, Vietnam. About 300 physicists

1 particle/km 2 /century

p + γ 2.7 K → N+ π Above E thr ≈ 7*10 19 eV, protons loose rapidly energy via pion photoproduction. Interaction length ≈ 6 Mpc Energy loss ≈ 20 % / interaction Greisen-Zatsepin-Kuzmin

AGASA sees a continuation of the spectrum beyond the GZK suppression Dashed curve represents the spectrum expected for extragalactic sources distributed unifomly in the Universe. Extremely poor statistics - only 11 events above eV

Auger hybrid detector Fluorescence Detector (FD) Longitudinal development of the shower Calorimetric measurement of the energy Calibration of the energy scale Direction of the shower 12% duty cycle ! Surface Detector (SD) Front of shower at ground Direction of the shower “High” statistics

Southern Observatory (Argentina) Very low population density (< 0.1 / km 2 ) Very good atmospheric conditions (clouds, aerosol…) 35 o S latitude 69 o W longitude ≈ 1400 m height ≈ 875 g/cm 2 Very flat region “Pampa Amarilla” Malargüe (Argentina) Future plan for Northern Observatory in Colorado (USA)

50 km Total area ~3000 km Surface detectors (“water tanks”) 1.5 km spacing 24 fluorescence telescopes 6 in each of 4 buildings The Auger Observatory About ¾ installed and operational Completion in 2007

A surface detector (“water tank”) installed in the Pampa

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

 -response ~ track e/  -response ~ energy  -signal of order em-signal Inclined:  em UP

SD calibration & monitoring single muons Noise Base-Temperature vs Time Signal-Height vs Time Signal-Height vs Base-Temp Single tank response Huge Statistics! Systematic error ~5% ± 3% ~100 p.e. VEM

Vertical Equivalent Muon (VEM)

Doublets DiaNoche 11m Time resolution Low energy events (~ eV) used to compare the time measurement of each tank : physical dispersion due~13 ns) Time precision of individual tanks ~ 12 ns

Young & Old Shower ‘young’ shower ‘old’ shower density falls by factor ~150 … by factor ~4

(m) ~1  eV ~10 20 eV Lateral Distribution Function ~ 14 km ~ 8 km One event of high energy:~10 20 eV,  ~60° 34 tanks ~60° LDF S=A [r/r s (1+r/r s )] -β r s = 700 m A, β from fit (β= 2-2.5) S(1000) energy estimator propagation time of 40 µs

Angular resolution from the surface detector depends on the number of tanks Improved for hybrid events: ~ 0.6 degrees

The FD telescope (Schmidt optics) Field of view 30x30 degrees Spherical mirror PMT camera Diaphragm UV Filter Shutter

The Schmidt optics C Spherical aberration Coma aberration Diaphragm Coma suppressed C C C spot F Spherical focal surface

Six Telescopes viewing 30°x30° each

Fluorescence Telescope Spherical mirror (R=3.4 m) Diaphragm and camera

Diaphragm, corrector ring and camera Field of view: 30 0 x30 0 Camera: 440 photomultipliers Aperture of the pixels: 1.5 0

Atmospheric Fluorescence Nitrogen emission spectrum 300 – 400 nm Photon yield as a function of height Error about 15%

FD Absolute Calibration Drum: uniform camera illumination pulsed light sources, several wavelengths and intensity light diffusing Tyvek walls light flux measured by absolutely calibrated PMT About 5 photons/ADC count

FD “TEST BEAM” Central Laser Facility 355 nm Steerable laser optical fiber SD tank

LaserMirror DAQ Backscattering (Raman) Elastic bcks. molecular/Rayleigh & aerosol/Mie LIDAR Atmospheric absorption

LIDAR Station Steerable system: “Shoot on shower” technique

Event FD on-line bin=100 ns

Background event

Longitudinal profile of showers from the FD telescopes Fit with empirical formula of Gaisser-Hillas Calorimetric measurement of the energy.

Another event well contained

Correction for energy loss (neutrinos, muons) 8 – 12 % at eV

New upper limit on photon fraction E 0 >10 EeV X max from showers longitudinal profile observed by the fluorescence detector ΔX max ≈ 25 g cm events events

Distribution of the differences Δ γ in standard deviations between primary photon prediction and data Δ γ = 2 – 3.8

New Photon Limit (29 events) HP: Haverah Park A1,A2: AGASA Constraint on top-down/non acceleration models End 2009: about 2% limit at 10 EeV, 15% at 35 EeV 16% upper limit

Comparison to AGASA Energy interval (1.0 – 2.5 EeV), angular scale 20° 2116 / ratio = 0.98 ± 0.02 ±0.01 (22% excess would give 2634 and a 10-  excess) Comparison to SUGAR Energy interval (0.8 – 3.2 EeV), angular scale 5° 286 / ratio = 0.98 ± 0.06 ± 0.01 (85% excess would give 536 and a  excess) Study of excess from the Galactic Center

Zenith angle dependence of the energy estimator S(1000)

Energy calibration – hybrid events Energy obtained by the calorimetric measurement of the fluorescence detector sets the absolute energy scale Simulation not needed. log 10 S(1000) log 10 E (EeV) FD energy Absolute calibration of the energy estimator S(1000) Corrected to 38 degrees

Statistics is now about ½ year of full Observatory (~7000 km 2 sr yr) Efficiency =100% above 3 EeV Systematic error on the energy ±~ 25%

Auger