Auger New Results G. Matthiae Universita’ e Sezione INFN di Roma “Tor Vergata”
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Auger New Results
G. MatthiaeUniversita’ 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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1 particle/km2/century
LHC c.m.
~ 1 / E3
Cosmic ray spectrum year 2000
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Cosmic ray spectrum - 2008
l
AGASA: surface arrayHiRes: fluorescence telescopesAuger: Hybrid
ankle
GZK
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e+e–
Interaction length
Attenuation length
Interaction with CMB GZK cutoffAbove E ≈ 6*1019 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 + π0
∆+ production
{γ from π0 , ν from π+}
e+ e- pair production isless effective, energy loss
≈ 0.1% / interactionProduces a “dip” in the spectrum (Berezinsky)Nuclei: also photodissociation
protons
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1 EeV = 1018 eV
PROTONS
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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)
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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
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AUGER Observatory
• Very flat region with low population density
• Good atmospheric conditions (clouds, aerosol)
350 S latitude
≈ 1400 m height ≈ 875 g/cm2
1600 Surface detectors (“water tanks”) 1.5 km spacing
24 fluorescence telescopes, 6 in each of 4 buildings
Total area ~3000 km2
nearly completed
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Water Tank in the Pampa
Solar PanelElectronics enclosure40 MHz FADC, local triggers, 10 Watts
Communication antenna
GPS antenna
Batterybox
Plastic tank with 12 tons of water
three 9”PMTs
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Calibration: Vertical Equivalent Muon (VEM) : ~ 90 p.e.
Selecting vertical muons with telescope scintillation counters
Dia Noche
Time resolution ~ 12 ns
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Young & Old Shower ‘young’ shower
strong e.m. component
‘old’ shower
signal dominates
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The FD telescope (Schmidt optics)Field of view 30x30 degrees
Spherical mirror
PMT camera
Diaphragm
UV Filter (300-400 nm)
Shutter
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Fluorescence Telescope
Spherical mirror (R=3.4 m)Camera with 440 PMTs
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FD ABSOLUTE CALIBRATIONDrum: a calibrate light source
uniformly illuminates the FD camera
Dru
m
Mirror reflectivity,
PMT sensitivity etc.,
are all included!
~ 5 photons /ADC 10% error
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Laser Mirror DAQ
Backscattering
Elastic bcks. molecular/Rayleigh &
aerosol/Mie
LIDAR
Atmospheric attenuation / shoot on shower technique
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FD “TEST BEAM”Central Laser Facility
355 nmSteerable laser
optical fiber
SD tank
Time correlation FD - SD
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Longitudinal profile of showers from the FD telescopes Fit with empirical formula of Gaisser-HillasCherenkov light subtractedCalorimetric measurement of the energy.
XX
XX
XXNXN
XX
max
0max
0max exp)(
0max
4 par
Nmax ~ E , Xmax ~ log E
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Correction for energy loss (neutrinos, muons)
p / Fe : 8 – 12 % at 1019 eV (10% ± 2%)eventually important to know the composition
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XmaxDepth of the maximum
Study of composition – mass of the primaries
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Xmax as a function of the energy
Compilationprevious data{
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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
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Limits on photon fraction (integral flux)
PRELIMINARY
~ 3 %
HP: Haverah ParkA1,A2: AGASAY: Yakutsk
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hmax
10 km
L
W
Neutrinos - Earth skimming
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Auger – no neutrino candidates
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Xmax measured over two decades of energy
(<A> ~ 5)Syst error on Xmax < 15 g /cm2
Mass composition: protons, light nuclei, Fe ?
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HiRes Group: astro-ph/0703099
5.1 +/- 0.7Power law index E-γ
HiRes Final data 2007
V. Berezinski: shallow minimum (“dip”) from e +e- production and pile-up of GZK particles
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Lateral Distribution Function
Auger - One event of high energy:~1020 eV, ~60°
34 tanks
LDFFit distance r from the core
S=A [r/rs (1+r/rs)] -β
rs = 700 mA, β from fit (β= 2-2.5)
S(1000) energy estimator
Sign
al (
VE
M)
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Energy calibration – hybrid eventsEnergy obtained by the calorimetric measurement of the fluorescence detector. Simulation not needed.
S(1000)Corrected to 380
EFD= a x S b
b = 1.08 ± 0.04
661 events
6x1019 eV
Error on the energy • 19 % statistical• 22% systematic (scale error) fluorescence yield/calibration
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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
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Detailed features of the spectrum better seen by taking difference with respect to
reference shape Js = A x E-2.69
GZK cut off Slope γ above 4x1019 eV: 4.0 ± 0.4
HiRes:5.1 ± 0.7
γ = 2.69 ± 0.02Fit E-γ
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0-60 degrees
60-80 degrees
ENERGY SPECTRUM
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Precision of the measurement of the direction
Vertical shower of energy 1019 eV activates 7-8 tanks
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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
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Super-galactic plane
Galactic coordinates
Border of the field of view
Doublet from Centaurus A(nearest AGN at ~ 4 Mpc)
27 events E > 57 EeV20 events correlate with AGN within 3.20
Véron &Véron-Cetty catalogue442 AGN (292 in f.o.v.)z<0.018 (75 Mpc)
RelativeRelativeexposureexposure
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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 zmax GZK
3- Maximum angular
separation deflections in B and angular resolution
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Number of events
E > 57 EeV
Correlated with AGN
ψ = 3.1 degree
Expected for isotropy
Exploratory scan1 Jan 04- 27 May 06
15 12 3.2
Second independent set27 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
Probability of observed configuration if distribution is isotropic: 10-5
5 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 = 3.10 • Maximum AGN redshift ( 0.018 corresponding to ~75 Mpc)• Energy threshold : 57 EeV
(1.7x10-3)
p = 0.21
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CR
AGN
Isotropic fluxThe 6 events at lowgalactic latitudes |b| < 120
ANGULAR SEPARATION FROM THE CLOSEST AGN
• catalogue incompleteness
• larger deflections in galactic B
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Deflection in the galactic magnetic field
Simulation(protons 60 EeV)
20 correlated events
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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 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
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Zenith angle dependence of the energy estimator S(1000)
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45
Rpt0
χi
χ0
Shower parameters from Fluorescence Detector
(single telescope)
1. Determination of the Shower-Detector Plane (SDP) is good
2. Time fit: t(χi) = t0 + Rp*tan [(χ0 - χi)/2]
Space reconstruction is inaccurate within the Shower Detector Plane.
shower
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AttenuationRayleigh attenuation length: 23 km at sea level
Vertical Aerosol Optical DensityVAOD (h) = ∫ α(z) dz
Attenuazione: exp{-VAOD(h)}
Not a good night
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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
Study of excess from the Galactic Center
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Effect of interaction with CMBV.Berezinsky et al.
• production of e+ e- pairs• photoproduction of pions
protons
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GZK and mass composition
Only protons and not too light nuclei are able to reach the Earth for energies above ~ 60 EeV