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

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

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

2 1 particle/km 2 /century LHC c.m. ~ 1 / E 3 Cosmic ray spectrum year 2000

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

4 e+e–e+e–  Interaction length Attenuation length Interaction with CMB GZK cutoff Above E ≈ 6*10 19 eV, protons loose rapidly energy via pion photoproduction. Energy loss ≈ 15 % / interaction. Interaction length = 5 – 10 Mpc Greisen-Zatsepin-Kuzmin p + γ CMB → n + π+ p + π 0 ∆ + production {γ from π 0, ν from π+} e+ e - pair production is less effective, energy loss ≈ 0.1% / interaction Produces a “dip” in the spectrum (Berezinsky) Nuclei: also photodissociation protons

5 1 EeV = eV PROTONS

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

7 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

8 AUGER Observatory Very flat region with low population density Good atmospheric conditions (clouds, aerosol) 35 0 S latitude ≈ 1400 m height ≈ 875 g/cm Surface detectors (“water tanks”) 1.5 km spacing 24 fluorescence telescopes, 6 in each of 4 buildings Total area ~3000 km 2 nearly completed

9 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

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

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

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

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

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

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

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

18 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 N max ~ E, X max ~ log E

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

20 X max Depth of the maximum Study of composition – mass of the primaries

21 Xmax as a function of the energy Compilation previous data {

22 Photon – the experimental method A  (SD) Shower front curvature  A (SD) Shower front thickness Fluorescence Detector Xmax from shower longitudinal profile. Surface Detector Shape of the front of the shower

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

24 h max 10 km L W Neutrinos - Earth skimming

25 Auger – no neutrino candidates

26 X max measured over two decades of energy ( ~ 5) Syst error on Xmax < 15 g /cm 2 Mass composition: protons, light nuclei, Fe ?

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

28 Lateral Distribution Function Auger - One event of high energy:~10 20 eV,  ~60° 34 tanks LDF Fit distance r from the core 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 Signal (VEM)

29 Energy calibration – hybrid events Energy obtained by the calorimetric measurement of the fluorescence detector. Simulation not needed. S(1000) Corrected to 38 0 E FD = a x S b b = 1.08 ± events 6x10 19 eV Error on the energy 19 % statistical 22% systematic (scale error) fluorescence yield/calibration

30 Energy spectrum (θ < 60 0 ) Exposure 7000 km 2 sr yr (3% error) (~ 1 year Auger completed) Exp. Observed > 4x ±9 75 > ± 3 1 Trigger efficiency =100 % above 3x10 18 eV

31 Detailed features of the spectrum better seen by taking difference with respect to reference shape J s = A x E GZK cut off Slope γ above 4x10 19 eV: 4.0 ± 0.4 HiRes: 5.1 ± 0.7 γ = 2.69 ± 0.02 Fit E -γ

32 0-60 degrees degrees ENERGY SPECTRUM

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

34 EVIDENCE OF ANISOTROPY AT HIGH ENERGY High-energy events (E > 5.7x10 19 eV) are correlated with AGNs at distance less than about 75 Mpc Angular correlation (~ 3 0 ) 9 November 2007

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

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

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

38 CR AGN Isotropic flux The 6 events at low galactic latitudes |b| < 12 0 ANGULAR SEPARATION FROM THE CLOSEST AGN catalogue incompleteness larger deflections in galactic B

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

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42 Conclusions 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 X max ? =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 (~ km 2 = 7 x Auger South ) FUTURE

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44 Zenith angle dependence of the energy estimator S(1000)

45 45 RpRp t0t0 χi χi χ0χ0 Shower parameters from Fluorescence Detector (single telescope) 1.Determination of the Shower-Detector Plane (SDP) is good 2.Time fit: t(χ i ) = t 0 + R p *tan [(χ 0 - χ i )/2] Space reconstruction is inaccurate within the Shower Detector Plane. shower

46 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

47 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) / ± 0.02 ± – / ± 0.02 ± – / ± 0.03 ± 0.01 Study of excess from the Galactic Center

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

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


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