“Un altro modo di guardare il cielo” NO – VE Venezia - April 15-18, 2008 “Un altro modo di guardare il cielo” Auger New Results G. Matthiae Universita’ e Sezione INFN di Roma “Tor Vergata”

Cosmic ray spectrum year 2000 ~ 1 / E3 1 particle/km2/century LHC c.m.

Cosmic ray spectrum - 2008 ankle GZK AGASA: surface array HiRes: fluorescence telescopes Auger: Hybrid Cosmic ray spectrum - 2008 l ankle GZK

Greisen-Zatsepin-Kuzmin Interaction with CMB GZK cutoff Above E ≈ 6*1019 eV, protons loose rapidly energy via pion photoproduction. Energy loss ≈ 15 % / interaction. Interaction length = 5 – 10 Mpc p + γ CMB → n + π+ p + π0 ∆+ production {γ from π0 , ν from π+} protons e+e– e+ e- pair production is less effective, energy loss ≈ 0.1% / interaction Produces a “dip” in the spectrum (Berezinsky) Attenuation length  Nuclei: also photodissociation Interaction length

PROTONS 1 EeV = 1018 eV

Horizon: maximum distance of the sources from which X % (for example 90 %) of the protons arrive on Earth with energy above a given value. Energy (EeV) 100 Mpc

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

AUGER Observatory Total area ~3000 km2 nearly completed 350 S latitude ≈ 1400 m height ≈ 875 g/cm2 Total area ~3000 km2 Surface detectors (“water tanks”) 1.5 km spacing 24 fluorescence telescopes, 6 in each of 4 buildings Very flat region with low population density Good atmospheric conditions (clouds, aerosol)

Water Tank in the Pampa Communication antenna GPS antenna 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

Calibration: Vertical Equivalent Muon (VEM) : ~ 90 p.e. Time resolution ~ 12 ns Selecting vertical muons with telescope scintillation counters Dia Noche

‘young’ shower strong e.m. component ‘old’ shower m signal dominates Young & Old Shower ‘young’ shower strong e.m. component ‘old’ shower m signal dominates

The FD telescope (Schmidt optics) Field of view 30x30 degrees Diaphragm Spherical mirror PMT camera Shutter UV Filter (300-400 nm)

Fluorescence Telescope Camera with 440 PMTs Spherical mirror (R=3.4 m)

FD ABSOLUTE CALIBRATION Drum: a calibrate light source uniformly illuminates the FD camera Mirror reflectivity, PMT sensitivity etc., are all included! Drum ~ 5 photons /ADC 10% error

molecular/Rayleigh & aerosol/Mie Atmospheric attenuation / shoot on shower technique LIDAR Backscattering Elastic bcks. molecular/Rayleigh & aerosol/Mie Laser Mirror DAQ

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

Longitudinal profile of showers from the FD telescopes Fit with empirical formula of Gaisser-Hillas Cherenkov light subtracted Calorimetric measurement of the energy. 4 par Nmax ~ E , Xmax ~ log E

Correction for energy loss (neutrinos, muons) p / Fe : 8 – 12 % at 1019 eV (10% ± 2%) eventually important to know the composition

Study of composition – mass of the primaries Xmax Depth of the maximum

Xmax as a function of the energy { Compilation previous data

Photon – the experimental method 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

Limits on photon fraction (integral flux) PRELIMINARY HP: Haverah Park A1,A2: AGASA Y: Yakutsk ~ 3 %

Neutrinos - Earth skimming L W 10 km hmax

Auger – no neutrino candidates

Xmax measured over two decades of energy Syst error on Xmax < 15 g /cm2 (<A> ~ 5) Mass composition: protons, light nuclei, Fe ?

HiRes Final data 2007 Power law index E-γ 5.1 +/- 0.7 Power law index E-γ HiRes Group: astro-ph/0703099 V. Berezinski: shallow minimum (“dip”) from e +e- production and pile-up of GZK particles

Auger - One event of high energy:~1020 eV, q ~60° 34 tanks Lateral Distribution Function LDF Fit distance r from the core S=A [r/rs (1+r/rs)] -β rs = 700 m A, β from fit (β= 2-2.5) S(1000) energy estimator Signal (VEM)

Energy calibration – hybrid events Energy obtained by the calorimetric measurement of the fluorescence detector. Simulation not needed. 661 events S(1000) 6x1019 eV Corrected to 380 EFD= a x S b b = 1.08 ± 0.04 Error on the energy 19 % statistical 22% systematic (scale error) fluorescence yield/calibration

Energy spectrum (θ < 600) Exposure 7000 km2 sr yr (3% error) (~ 1 year Auger completed) Exp. Observed > 4x1019 179±9 75 > 1020 38±3 1 Trigger efficiency =100 % above 3x1018 eV

Fit E-γ GZK cut off Detailed features of the spectrum better seen by taking difference with respect to reference shape Js = A x E-2.69 Fit E-γ γ = 2.69 ± 0.02 GZK cut off Slope γ above 4x1019 eV: 4.0 ± 0.4 HiRes: 5.1 ± 0.7

ENERGY SPECTRUM 0-60 degrees 60-80 degrees

Precision of the measurement of the direction Vertical shower of energy 1019 eV activates 7-8 tanks

EVIDENCE OF ANISOTROPY AT HIGH ENERGY High-energy events (E > 5.7x1019 eV) are correlated with AGNs at distance less than about 75 Mpc Angular correlation (~ 30) 9 November 2007

Véron &Véron-Cetty catalogue 442 AGN (292 in f.o.v.) z<0.018 (75 Mpc) 27 events E > 57 EeV 20 events correlate with AGN within 3.20 Galactic coordinates Relative exposure Doublet from Centaurus A (nearest AGN at ~ 4 Mpc) Border of the field of view Super-galactic plane

ANALYSIS METHOD Three parameter scan to find the minimum of P 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 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

Maximum AGN redshift ( 0.018 corresponding to ~75 Mpc) Set of parameters for the minimum P corresponding to maximum correlation with AGN Angular separation ψ = 3.10 Maximum AGN redshift ( 0.018 corresponding to ~75 Mpc) Energy threshold : 57 EeV p = 0.21 Number of events E > 57 EeV Correlated with AGN ψ = 3.1 degree Expected for isotropy Exploratory scan 1 Jan 04- 27 May 06 15 12 3.2 Second independent set 27 May 06–31 Aug 07 13 8 2.7 Full data set (about 1.2 year full Auger) 27 20 5.6 Full data set excluding region of the galactic plane (|b| > 12 degree) 21 19 5.0 (1.7x10-3) Probability of observed configuration if distribution is isotropic: 10-5 5 of the 7 events not correlated are close to the galactic plane

ANGULAR SEPARATION FROM THE CLOSEST AGN The 6 events at low galactic latitudes |b| < 120 Isotropic flux catalogue incompleteness larger deflections in galactic B CR AGN

Deflection in the galactic magnetic field Simulation (protons 60 EeV) 20 correlated events

Conclusions FUTURE Auger North (Colorado, US) to study Auger observes the GZK steepening of the energy spectrum confirming HiRes results (very high energy events are of extra-galactic origin). Correlation with AGNs (E > 57 EeV). Direct evidence of extra-galactic origin. Identification of the sources. ~ 25 events/year Interplay of different observables - Composition at very high-energy: protons or mixture of protons and light nuclei as indicated by Xmax ? <A>=5 ? Shape of the GZK steepening. Energy calibration (22% scale error at present) Horizon ( calculation gives 75 Mpc  80 – 100 EeV). Magnetic field deflection (small for protons !) More statistics and better control of the systematic errors needed ! Auger North (Colorado, US) to study northern sky (~ 20000 km2 = 7 x Auger South) FUTURE

Zenith angle dependence of the energy estimator S(1000)

Shower parameters from Fluorescence Detector (single telescope) Determination of the Shower-Detector Plane (SDP) is good Time fit: t(χi) = t0 + Rp*tan [(χ0 - χi)/2] Space reconstruction is inaccurate within the Shower Detector Plane. shower t0 Rp χi χ0

Attenuation Rayleigh attenuation length: 23 km at sea level Vertical Aerosol Optical Density VAOD (h) = ∫ α(z) dz Attenuazione: exp{-VAOD(h)} Not a good night

Study of excess from the Galactic Center Observation of an excess from the region of the Galactic centre at the level of 4.5 σ was reported by AGASA (1.22 ± 0.05) in angular cone of 20 degree radius. The Auger Observatory is suitable for these studies because the Galactic centre (constellation of Sagittarius) lies well in the field of view of the experiment. In the Auger data there is no indication of a statistically significant excess Energy interval (eV) Nobs/Nexp Ratio (errors: stat, syst) 1017.9 -- 1018.3 3179 / 3154 1.01 ± 0.02 ± 0.01 1018 – 1018.4 2116 / 2160 0.98 ± 0.02 ± 0.01 1018.1 – 1018.5 1375 / 1395 0.99 ± 0.03 ± 0.01

Effect of interaction with CMB V.Berezinsky et al. protons Effect of interaction with CMB V.Berezinsky et al. production of e+ e- pairs photoproduction of pions

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