Diapositiva 1

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Results on Ultra-High Energy Cosmic Rays from the
Pierre Auger Observatory
Valerio Verzi INFN Roma Tor Vergata for the
Pierre Auger Collaboration
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COSMIC RAYS SPECTRUM (2008)
l
Flux x E2.5
UHECR
1020 eV
1 particle/km2/century!
3
WHERE DO COME FROM?
only few candidates
Centaurus A
B
AGN at only 3.4 Mpc

AGN
Trajectory in galactic and inter-galactic B
1020 eV
1018 eV
Hillas diagram
R
more details in G.Farrars talk
Back to origin!
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Greisen-Zatsepin-Kusmin (GZK)
Interaction with CMB
Modification of the spectrum
l510 Mpc
GZK cutoff
UHECR sources must be closer than 50-100 Mpc!
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ATMOSPHERIC SHOWERS
10 li 30 X0
at ground millions of particles detectors in
coincidence
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AUGER HYBRID DETECTOR

• Fluorescence Detector (FD)
• fluorescence light from the N2 de-excitation
• () Longitudinal shower development
• calorimetric measurement of E
• sensitivity to CR mass (Xmax)
• (-) Duty cicle 10

FD

• Surface Detector (SD)
• detection of the shower front at ground
• () Duty cicle 100 (important for UHECR)
• (-) Shower size at ground ? E (systematics)
• calibration from FD

SD
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PIERRE AUGER OBSERVATORY
Malargue - Argentina
SD 1600 water Cherenkov detec. on a 1.5
km hexagonal grid
3000 km2
FD 4 x 6 fluorescence telescopes
50 km
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PIERRE AUGER OBSERVATORY
Malargue - Argentina
SD 1600 water Cherenkov detec. on a 1.5
km hexagonal grid
3000 km2
Installation completed this year
FD 4 x 6 fluorescence telescopes
50 km
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SD TANKS
1.5 km
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FLUORESCENCE TELESCOPE
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WATER TANK
Communication antenna
GPS antenna
Electronics enclosure 40 MHz FADC, local
triggers, 10 Watts
Solar Panel
Plastic tank with 12 tons of water
Battery box
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TANK SIGNAL
?
m
PMT
m
diffusive Tyvek

• m-response track
• e/g-response energy

1.2 m 3 Xo
Cerenkov light
water
old shower m signal dominates
young shower strong e.m. component
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SD SHOWER RECONSTRUCTION
Shower front from particle arrival times
Core position and S(1000) from LDF (NGK) fit
Signal (VEM)
Distance from the core (m)
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SD SHOWER RECONSTRUCTION
Shower front from particle arrival times
Core position and S(1000) from LDF (NGK) fit
Signal (VEM)
Shower axis resolution
Distance from the core (m)
E gt 1019 eV 10
zenit (degrees)
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SD SHOWER RECONSTRUCTION
Shower front from particle arrival times
Core position and S(1000) from LDF (NGK) fit
Signal (VEM)
S(1000) E
Distance from the core (m)
FD calorimetric measurement
No simulations!
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FD TELESCOPE

• Spherical mirror 3.4m radius of curvature

Schmidt optics
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FD TELESCOPE

• 2.2 m diameter diaphragm corrector ring, UV
  optical filter

Schmidt optics
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FD TELESCOPE

• Camera (focal surface) - 440 PMTs 30ox30o FOV
  pixel 1.5o spot 15 mm (0.5o)

Schmidt optics
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FD EVENT
bin100 ns
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FD ENERGY SCALE
Energy deposit
N?
Airfly spectrum
Fluorescence yield from laboratory measurements
5 photons/MeV at 337 nm
Shower energy uncertainty 15
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FD ENERGY SCALE
Atmospheric transmission
N?
N?
at diaphragm
Atmospheric monitoring aerosols, clouds, density
profiles (Lidar, Central Laser Facility, Ballons,
)
Shower energy uncertainty 5
22
FD ENERGY SCALE
N?
PMTs signal
at diaphragm
N?
Drum absolute calibration uniform camera
illumination with a calibrated
light source
5 g/ADC
Shower energy uncertainty 10
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FD ENERGY SCALE
E 3.5 1019 eV
Expected profile fitted Gaisser-Hillas function
Xmax 810 g/cm2
Ecal Xmax
X
Ecal
E
only a 10 model dependent correction
Shower energy uncertainty 4
Log E
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SD CALIBRATION USING FD ENERGY
S(1000)
HYBRID SHOWERS
S(1000,q380) with CIC
LINEAR FIT
50 VEM 1019 eV
661 events
Statistical uncertainty 7 at 1019 eV 15 at
1020eV
PRL 101, 061101 (2008)
FD syst. uncertainty (22) dominates
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AUGER SCIENCE
SPECTRUM
COMPOSITION
SOURCES
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ENERGY SPECTRUM - qlt600
Data up to 31/08/07
Aperture 7000 km2 sr yr
1 year Auger completed 2 x HIRES 4 x AGASA
PRL 101, 061101 (2008)
Full efficiency above 1018.5 eV ? 3 uncertainty
on aperture
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ENERGY SPECTRUM - qlt600
Data up to 31/08/07
Exp. Observed gt 4x1019
1673 66 gt 1020 351 1
Aperture 7000 km2 sr yr
1 year Auger completed 2 x HIRES 4 x AGASA
PRL 101, 061101 (2008)
Evidence of GZK cutoff
Full efficiency above 1018.5 eV ? 3 uncertainty
on aperture
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ENERGY SPECTRUM - qlt600
Fit E-?
HiRes 5.1 0.7
? 4.2 0.4
? 2.69 0.06
difference with respect to reference shape Js
A x E-2.69
GZK cut off
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ENERGY SPECTRUM
Comparison of the three Auger spectra -
consistency
0-60 degrees
Different reconstruction
60-80 degrees
Exposure from simulation
Ankle
ICRC 07
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Auger combined compared to Hires and Agasa
Fairly agreement within systematic uncertainties
ICRC 07
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AUGER SCIENCE
SPECTRUM
COMPOSITION
SOURCES
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ELONGATION RATE
(lt Agt 5)
Change of slope correlation with ankle ?
preliminary
Systematics lt 15 g /cm2
Not proton dominated composition at the highest
energies
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SENSITIVITY TO PHOTON SHOWERS
Fluorescence Detector Xmax from
shower longitudinal profile.
(SD) Shower front curvature

Surface Detector Shape of the front of the shower
(SD) Shower front thickness
A
g
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PHOTON FRACTION LIMIT
preliminary
3
Top Down models Super Heavy Dark Matter Relic
of topological defects
HP Haverah Park A1,A2 AGASA Y Yakutsk
Astro. Ph. 29 (2008), 243.
Astro. Ph. 27 (2007), 155.
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NEUTRINO FLUX LIMIT
Signature very inclined showers with high
e.m. signal component hadronic showers signal
dominated by muon component
87 degrees
PRL 100 (2008), 211101.
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AUGER SCIENCE
SPECTRUM
COMPOSITION
SOURCES
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GALACTIC CENTER ANISOTROPIES
H.E.S.S. TeV g-ray from Sagittarius A
Excess in previous experiments
GC
AGASA 2.5s
SUGAR 2.9s

• larger exposure
• GC lies well in the f.o.v.

Auger
No statistically significant excess in Auger data

• angular windows
• AGASA and SUGAR
• 10 and 20 around the GC (charged CRs)
• 1 around the GC
• 0.1 lt E lt 1 EeV (photons)
• 1 lt E lt 10 EeV (neutrons)

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EVIDENCE OF ANISOTROPY
Correlation of the
Highest-Energy (gt5.7x1019 eV) Cosmic Rays with
Nearby (lt75 Mpc) Extragalactic Objects
Centaurus A
Astro. Ph. 29 (2008), 188.
Science 318 (2007), 939.
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EVIDENCE OF ANISOTROPY
Véron Véron-Cetty catalogue 442 AGN (292 in
f.o.v.) zlt0.017 (71 Mpc)
27 events E gt 57 EeV 3.20 radius
galactic coordinates
Doublet from Centaurus A
Border of the f.o.v.
Relative exposure
Super-galactic plane
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ANALYSIS METHOD
CR
Fix candidate sources and maximum angular
distance y
Prob. gtk of the N events from isotropic flux
correlate by chance with sources (lty)
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ANALYSIS METHOD
CR
Fix candidate sources and maximum angular
distance y
Prob. gtk of the N events from isotropic flux
correlate by chance with sources (lty)
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RESULTS
Absolute minimum
zmax 0.017 (71 Mpc)
E gt 57 EeV
y 3.20
Selected events Events correlated Expected for isotropy
27 20 5.6
1.2 year full Auger
Isotropy hypothesis rejected with at least 99
confidence level
exploratory scan

(01/01/04- 27/05/06) confirmation on an
independent data set
(27/05/06- 31/08/07)
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WHAT ABOUT NOT CORRELATED EVENTS?
Events with low galactic latitudes b lt 120
Isotropic flux

• catalogue
• incompleteness
• larger deflections
• in galactic
• magnetic field

Selected events Events correlated Expected for isotropy
Full data sample 27 20 5.6
b gt 120 21 19 5.0
6 events less with 5 not correlated
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THE ANGULAR SEPARATION Y

• angular resolution 10 lt y (3.20)

• y determined by galactic and inter-galactic
  magnetic fields

Simulation including galactic magnetic field
simulated protons (isotropy)
27 observed events
y3.20
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THE ANGULAR SEPARATION Y

• angular resolution 10 lt y (3.20)

• y determined by galactic and inter-galactic
  magnetic fields

Simulation including galactic magnetic field
simulated protons (isotropy)
27 observed events
y3.20
correlated events are likely protons
but elongation rate suggests a mixed composition
at the highest energies
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CONNECTION TO THE GZK CUT OFF
events E gt 5.7 1019 eV
spectrum
sources lt 71 Mpc
flux reduced by 50
but
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CONNECTION TO THE GZK CUT OFF
events E gt 5.7 1019 eV
spectrum
sources lt 71 Mpc
flux reduced by 50
but
GZK Horizon is 200 Mpc
maximum distance of the sources from which 90
of the protons arrive on Earth with energy above
a given value.
90
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CONNECTION TO THE GZK CUT OFF
events E gt 5.7 1019 eV
spectrum
sources lt 71 Mpc
flux reduced by 50
but
GZK Horizon is 200 Mpc
maximum distance of the sources from which 90
of the protons arrive on Earth with energy above
a given value.
90
For an 30 energy estimator the Horizon would be
100 Mpc
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CONNECTION TO THE GZK CUT OFF
events E gt 5.7 1019 eV
spectrum
sources lt 71 Mpc
flux reduced by 50
but
GZK Horizon is 200 Mpc
maximum distance of the sources from which 90
of the protons arrive on Earth with energy above
a given value.
90
For an 30 energy estimator the Horizon would be
100 Mpc
Uncertainty on energy scale 25
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CONCLUSIONS

• Auger is fully operational exposure 1 year of
  Auger completed

• UHECR anisotropy

angular distribution similar to that of AGN
within 70 Mpc sources are of
extra-galactic origin primaries are likely
protons which interact with CMB radiation (GZK)
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CONCLUSIONS

• Auger is fully operational exposure 1 year of
  Auger completed

• UHECR anisotropy

angular distribution similar to that of AGN
within 70 Mpc sources are of
extra-galactic origin primaries are likely
protons which interact with CMB radiation (GZK)

• no photon and neutrino candidates
• (disfavour TOP-DOWN models)

• evidence of GZK cut-off in the spectrum
  confirming
• HIRES data

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CONCLUSIONS

• Auger is fully operational exposure 1 year of
  Auger completed

• UHECR anisotropy

angular distribution similar to that of AGN
within 70 Mpc sources are of
extra-galactic origin primaries are likely
protons which interact with CMB radiation (GZK)

• no photon and neutrino candidates
• (disfavour TOP-DOWN models)

• evidence of GZK cut-off in the spectrum
  confirming
• HIRES data

but

• Xmax studies disfavour a proton dominated
  composition at the highest energies

• Consistency or not with the GZK horizon?

• Two events from CenA, none from Virgo. Why?

• Need more statistics ( 70 events/year above
  4x1019 eV)
• and better control of systematics

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FUTURE DEVELOPMENT
Auger North (Colorado, US) (talk of prof.
J.Bluemer)
Full sky coverage
Array 8000 square miles 20000 km2
7 x Auger South)
events above 4x1019 eV (GZK cutoff)
Auger South 70 events/year Auger North 500
events/year
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(No Transcript)
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BACK UP SLIDES
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TANK CALIBRATION
Vertical
m
PMT
m
diffusive Tyvek
Online calibration with background muons (2 kHz)
1.2 m 3 Xo
Cerenkov light
water
scintillator
1 VEM 100 p.e.
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TIME RESOLUTION
Low energy events ( 1017 eV) used to compare the
time measurement of each tank
GPS intrinsic time resolution 8 ns
Time precision of each individual tank 12 ns
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SD-TANK TRIGGER
Threshold Trigger 20 Hz
Time Over Threshold Trigger Hz
5 ?s
SD-EVENT TRIGGER
hottest tank surrounded by 6 working stations
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SD SHOWER RECONSTRUCTION
distance from the core
size parameter
Lateral distribution function (LDF) NGK
slope parameter
(ß(q) 2-2.5)
S(1000) and the core position from the fit
core
S(1000)
Signal (VEM)
34 tanks
distance from the core (m)
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SD CALIBRATION USING FD ENERGY
vertical shower
inclined shower
for the same energy and mass S(10000)gt S(1000q)
Xg
Xg/cosq
Attenuation curve derived with constant intensity
cut technique
ground
for each shower determine the signal that
would have had at 380
S38 S(1000,380)
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SD CALIBRATION USING FD ENERGY
LINEAR FIT
19
measurement of the energy resolution
16-S38 8-EFD
PRL 101, 061101 (2008)
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SD APERTURE
Full efficiency above 3x1018 eV
20.000 events above 3 1018 eV
Aperture 7000 km2 sr yr (3 error)
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ELONGATION RATE
64
Comparison with PAO data, without and with
acceptance
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ELONGATION RATE
66
ELONGATION RATE
p - EPOS
Fe - EPOS
Fe - QGSJETII
p - QGSJETII
proton
iron

• The mass spectrum is not proton dominated at the
  highest energies
• Ambiguous interpretation uncertainties of
  hadronic interactions at highest energies

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GALACTIC CENTER ANISOTROPIES
Angular window
Windows centred in the GC
Nobs/Nexp
Ratio (err. stat, syst)
1.30 (G) 192.1 / 191.2 1.00 0.07 0.01
100 5663 / 5657 1.00 0.02 0.01
200 22274 / 22440 0.99 0.01 0.01
0.80 (G) 16.9 / 17.0 0.99 0.17 0.01
100 1463 / 1365 1.07 0.04 0.01
200 5559 / 5407 1.03 0.02 0.01

search for photons
GC lies well in the Auger f.o.v.
0.1 lt E lt 1 EeV
search for neutrons
1 lt E lt 10 EeV
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ANISOTROPY
Expected for isotropy
Events correlated
Events
Probability to see such anisotropy with an
isotropic flux 10-5
5 of the 7 events not correlated are close to
the galactic plane
1.7 10-3
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Red dots 13 HiRes events (claim consistent with
isotropy) Black dots 27 Auger events
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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