Valerio VerziINFN Roma Tor Vergata
for the Pierre Auger Collaboration
Results on Ultra-High Energy Cosmic Rays from the
Pierre Auger Observatory
l
COSMIC RAYS SPECTRUM (2008)
Flux x E2.5
3E
1Flux
1 particle/km2/century!
~ 1020 eV
UHECR
WHERE DO COME FROM?
B
R
Hillas diagram
B R
E
only few candidates
1018 eV 1020 eV
Centaurus A
AGN at only 3.4 Mpc
•
Trajectory in galactic and inter-galactic B
Back to origin!
AGN
more details in G.Farrar’s talk
Greisen-Zatsepin-Kusmin (GZK)
p CMB→ N
Interaction with CMB Modification of the spectrum
UHECR sources must be closer than 50-100 Mpc!
epe
Nπ
5÷10 Mpc
GZK cutoff
10 i
30 X0
ATMOSPHERIC SHOWERS
at ground millions of particles… detectors in coincidence
AUGER – HYBRID DETECTOR
FD
SD
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
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%
PIERRE AUGER OBSERVATORY
FD 4 x 6 fluorescence telescopes
50 km
Malargue - Argentina SD 1600 water Cherenkov detec. on a 1.5 km hexagonal grid
3000 km2
PIERRE AUGER OBSERVATORY
FD 4 x 6 fluorescence telescopes
50 km
Malargue - Argentina SD 1600 water Cherenkov detec. on a 1.5 km hexagonal grid
3000 km2
Installation completed this year
1.5 km
SD TANKS
FLUORESCENCE TELESCOPE
WATER TANK
Solar PanelElectronics enclosure40 MHz FADC, local triggers, 10 Watts
Communication antenna
GPS antenna
Batterybox
Plastic tank with 12 tons of water
three 9”PMTs
diffusive Tyvek• -response ~ track
• e/-response ~ energy
TANK SIGNAL
‘old’ showersignal dominates
‘young’ showerstrong e.m. component
PMT
water
Cerenkovlight
1.2 m ~ 3 X
o
Distance from the core (m)
SD SHOWER RECONSTRUCTION
1.5 km
shower front
Shower front from particle arrival times
Core position and S(1000) from LDF (NGK) fit
Sign
al
(VE
M)
Distance from the core (m)
SD SHOWER RECONSTRUCTION
1.5 km
shower front
Shower front from particle arrival times
Core position and S(1000) from LDF (NGK) fit
Sign
al
(VE
M)
Sh
ower
axi
s re
solu
tion
zenit (degrees)
E > 1019 eV~ 10
Distance from the core (m)
SD SHOWER RECONSTRUCTION
1.5 km
shower front
Shower front from particle arrival times
Core position and S(1000) from LDF (NGK) fit
Sign
al
(VE
M)S(1000) ~ E
FD calorimetric measurement
No simulations!
Schmidt optics
FD TELESCOPE
Spherical mirror 3.4m radius of curvature
Schmidt optics
FD TELESCOPE
2.2 m diameter diaphragm corrector ring, UV optical filter
Schmidt optics
FD TELESCOPE
Camera (focal surface) - 440 PMT’s 30ox30o FOV pixel = 1.5o spot: 15 mm (0.5o)
bin=100 nsFD EVENT
Nγ
FD ENERGY SCALEdEdX
Energydeposit
Fluorescence yield from laboratory measurements
Shower energy uncertainty ~ 15%
5 photons/MeV at 337 nm
Airflyspectrum
Atmospheric monitoring aerosols, clouds, density profiles(Lidar, Central Laser Facility,Ballons, …)
Atmospheric transmission
Nγat diaphragm
Nγ
Shower energy uncertainty ~ 5%
FD ENERGY SCALE
Nγat diaphragm
Nγ
PMT’s signal
Drum absolute calibration uniform camera illumination with a calibrated light source
Shower energy uncertainty ~ 10%
~ 5 /ADC
FD ENERGY SCALE
Xmax~ 810 g/cm2
E ~ 3.5 1019 eVExpected profile:fitted Gaisser-Hillas function
Ecal
EEcal
Ecal Xmax
Log E
dEdX
X
only a 10% model dependent correction
E
Shower energy uncertainty ~ 4%
FD ENERGY SCALE
SD CALIBRATION USING FD ENERGY
S(1000,=380) with CIC
04.008.1 B
BFD SAE 38
FD syst. uncertainty (22%) dominates
PRL 101, 061101 (2008)
LINEAR FIT
50 VEM ~ 1019 eV
HYBRID SHOWERS
Statistical uncertainty7% at 1019 eV15% at 1020eV
S(1000)
661 events
SPECTRUM
COMPOSITION
SOURCES
AUGER SCIENCE
ENERGY SPECTRUM - <600
PRL 101, 061101 (2008)
Full efficiency above 1018.5 eV 3% uncertainty on aperture
Data up to31/08/07
Aperture7000 km2 sr yr
~ 1 year Auger completed 2 x HIRES4 x AGASA
ENERGY SPECTRUM - <600
Exp. Observed> 4x1019 167±3 66
> 1020 35±1 1
Evidence of GZK cutoff
PRL 101, 061101 (2008)
Data up to31/08/07
Aperture7000 km2 sr yr
~ 1 year Auger completed 2 x HIRES4 x AGASA
Full efficiency above 1018.5 eV 3% uncertainty on aperture
γ = 2.69 ± 0.06
HiRes: 5.1 ± 0.7
γ = 4.2 ± 0.4
Fit E-γ
difference with respect to reference shape Js = A x E-2.69
GZK cut off
ENERGY SPECTRUM - <600
0-60 degrees 60-80 degrees
Comparison of the three Auger spectra - consistency
ENERGY SPECTRUM
ICRC 07
Different reconstruction
Exposure from simulation
Ankle
Auger combined compared to Hires and Agasa
Fairly agreement within systematic uncertainties
ICRC 07
SPECTRUM
COMPOSITION
SOURCES
AUGER SCIENCE
ELONGATION RATE
Not proton dominated composition at the highest energies
Change of slope
correlation with ankle ?
Systematics< 15 g /cm2
preliminary
(< A> ~ 5)
SENSITIVITY TO PHOTON SHOWERS
Fluorescence Detector
Xmax from shower
longitudinal profile.
A(SD) Shower front curvature
A(SD) Shower front thickness
Surface Detector
Shape of the front of the shower
preliminary
Astro. Ph. 29 (2008), 243. Astro. Ph. 27 (2007), 155.
PHOTON FRACTION LIMIT
HP: Haverah ParkA1,A2: AGASAY: Yakutsk
~ 3 % Top Down models:
Super HeavyDark Matter
Relic of “topologicaldefects”
Signature: very inclined showers with high e.m.signal component
hadronic showers: signal dominated by muon component
87 degrees
NEUTRINO FLUX LIMIT
PRL 100 (2008), 211101.
SPECTRUM
COMPOSITION
SOURCES
AUGER SCIENCE
GALACTIC CENTER ANISOTROPIES
Excess in previous experiments
AGASA 2.5SUGAR 2.9
angular windows:• AGASA and SUGAR • 10° and 20° around the GC (charged CR’s) • 1° around the GC
• 0.1 < E < 1 EeV (photons)• 1 < E < 10 EeV (neutrons)
H.E.S.S.: TeV -ray from Sagittarius A*
No statistically significant excess in Auger data
Auger: • larger exposure• GC lies well in the f.o.v.
GC
EVIDENCE OF ANISOTROPY
Correlation of the Highest-Energy (>5.7x1019 eV)
Cosmic Rays with Nearby (<75 Mpc) Extragalactic Objects
Astro. Ph. 29 (2008), 188.Science 318 (2007), 939.
Centaurus A
Super-galactic plane
galacticcoordinates
Border of the f.o.v. Doublet from Centaurus A
27 eventsE > 57 EeV3.20 radius
Véron &Véron-Cetty catalogue442 AGN (292 in f.o.v.)z<0.017 (71 Mpc)
Relative exposureRelative exposure
EVIDENCE OF ANISOTROPY
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 CR
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 maximum anisotropy (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
CR
RESULTS
1.2 year full Auger
zmax = 0.017 (71 Mpc) E > 57 EeV = 3.20
Absolute minimum
Selected events
Events correlated
Expected for isotropy
27 20 5.6
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)
WHAT ABOUT NOT CORRELATED EVENTS?
CR
closest AGN
Isotropic fluxEvents with lowgalactic latitudes |b| < 120
• catalogue incompleteness
• larger deflections in galactic magnetic field
Selected events
Events correlated
Expected for isotropy
Full data sample 27 20 5.6
|b| > 120 21 19 5.0
6 events less with 5 not correlated
THE ANGULAR SEPARATION • angular resolution ~ 10 < (=3.20)
• determined by galactic and inter-galactic magnetic fields
Simulation including galactic magnetic field
27 observed events
=3.20
simulated protons (isotropy)
THE ANGULAR SEPARATION • angular resolution ~ 10 < (=3.20)
• determined by galactic and inter-galactic magnetic fields
Simulation including galactic magnetic field
deflection E
60EeVZ
correlated events are likely protons
27 observed events
=3.20
simulated protons (isotropy)
but elongation rate suggests a mixed composition at the highest energies …
CONNECTION TO THE GZK CUT OFF
spectrumevents E > 5.7 1019 eV
flux reduced by 50%
sources < 71 Mpc
but …
CONNECTION TO THE GZK CUT OFF
spectrumevents E > 5.7 1019 eV
flux reduced by 50%
sources < 71 Mpc
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%
CONNECTION TO THE GZK CUT OFF
spectrumevents E > 5.7 1019 eV
flux reduced by 50%
sources < 71 Mpc
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
CONNECTION TO THE GZK CUT OFF
spectrumevents E > 5.7 1019 eV
flux reduced by 50%
sources < 71 Mpc
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%
Uncertainty on energy scale ~ 25%
For an +30% energy estimator the Horizon would be ~100 Mpc
CONCLUSIONS• Auger is fully operational: exposure ~ 1 year of Auger completed
angular distribution similar to that of AGN within ~ 70 Mpc sources are of extra-galactic originprimaries are likely protons which interact with CMB radiation (GZK)
• UHECR anisotropy
CONCLUSIONS• Auger is fully operational: exposure ~ 1 year of Auger completed
angular distribution similar to that of AGN within ~ 70 Mpc sources are of extra-galactic originprimaries are likely protons which interact with CMB radiation (GZK)
• UHECR anisotropy
• evidence of GZK cut-off in the spectrum confirming HIRES data
• no photon and neutrino candidates (disfavour TOP-DOWN models)
CONCLUSIONS• Auger is fully operational: exposure ~ 1 year of Auger completed
angular distribution similar to that of AGN within ~ 70 Mpc sources are of extra-galactic originprimaries are likely protons which interact with CMB radiation (GZK)
• UHECR anisotropy
• evidence of GZK cut-off in the spectrum confirming HIRES data
• no photon and neutrino candidates (disfavour TOP-DOWN models)
Consistency or not with the GZK horizon?
Two events from CenA, none from Virgo. Why?
but …
Xmax studies disfavour a proton dominated composition at the highest energies
• Need more statistics (~ 70 events/year above 4x1019 eV)
and better control of systematics
Auger North (Colorado, US)(talk of prof. J.Bluemer)
Array: 8000 square miles ≈ 20000 km2 ≈ 7 x Auger South)
Full sky coverage
FUTURE DEVELOPMENT
Auger South: ~ 70 events/yearAuger North: ~ 500 events/year
events above 4x1019 eV (GZK cutoff)
BACK UP SLIDES
diffusive Tyvek
TANK CALIBRATION PMT
water
Cerenkovlight
1.2 m ~ 3 X
o
scintillator
Vertical
1 VEM ≈ 100 p.e.
Online calibration with background muons (2 kHz)
muon peak VEM peak
Dia Noche
11m
Doublets Low energy events (~ 1017 eV) used to compare the time measurement of each tank
Time precision of each individual tank ~ 12 ns
GPS intrinsic time resolution 8 ns
TIME RESOLUTION
SD-TANK TRIGGERThreshold Trigger~ 20 Hz
Time Over Threshold Trigger~ Hz
5 s
hottest tank surrounded by 6 working stations
SD-EVENT TRIGGER
Lateral distribution function (LDF)
NGK
1700
700
1000)1000()(
rrSrS
size parameter
slope parameter
S(1000) and the core position from the fit
core
distance from the core
S(1000)
distance from the core (m)
Sign
al
(VE
M)
34 tanks
SD SHOWER RECONSTRUCTION
(β) 2-2.5)
SD CALIBRATION USING FD ENERGY
ground
Xg Xg/cos
vertical shower inclined shower for the same energy and massS(1000;0)> S(1000
for each shower determine
the signal that would have had at 380
Attenuation curve derived with constant intensity cut technique
S38 = S(1000,380)
SD CALIBRATION USING FD ENERGY
PRL 101, 061101 (2008)
LINEAR FIT19%
measurement of the energy resolution
16%-S38
8%-EFD
SD APERTURE
(t)dtareatriggerAperture
Full efficiency above 3x1018 eV
Aperture 7000 km2 sr yr (3% error) ~20.000 events above 3 1018 eV
ELONGATION RATE
Comparison with PAO data, without and with acceptance
ELONGATION RATE
ELONGATION RATE
Fe - EPOS
p - EPOS
Fe - QGSJETIIp - QGSJETII
• The mass spectrum is not proton dominated at the highest energies
• Ambiguous interpretation: uncertainties of hadronic interactions at highest energies
proton
iron
p0pmax clnAE/ElnDX
GALACTIC CENTER ANISOTROPIES
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
Angular window Nobs/Nexp Ratio (err.: stat, syst)
GC lies well in the Auger f.o.v.
Windows centred in the GC:
0.1 < E < 1 EeV
1 < E < 10 EeV
search for photons
search for neutrons
ANISOTROPYEvents Events
correlatedExpected for
isotropy
Exploratory scan1 Jan 04- 27 May 06
zmax = 0.018
E > 56 EeV = 3.10
15 12 3.2
Test on an independent data set 27 May 06- 31 Aug 07 **running prescription
13 8 2.7
Full data set 1.2 year full Auger *
zmax = 0.017 (71 Mpc)
E > 57 EeV = 3.20
27 20 5.6
Full data set excluding region of the galactic plane(|b| > 120)
21 19 5.0
*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
Red dots: 13 HiRes events (claim consistent with isotropy)
Black dots: 27 Auger events
GZK and mass composition
Only protons and not too light nuclei are able to reach the Earth for energies above ~ 60 EeV