Cosmic Rays from 10 16 to 10 18 eV. Open Problem and Experimental Results. (KASCADE-Grande view)
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Cosmic Rays from 1016 to 1018 eV. Open Problem and Experimental Results.
(KASCADE-Grande view)
Very High Energy Phenomena in the UniverseXLIVth Rencontres de Moriond
La Thuile 1-8 February 2009
Andrea ChiavassaUniversità di Torino
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Energy range covered in this talk2nd kneeIron knee??Transition from Galactic to ExtraGalactic Cosmic Rays??
knee
2nd knee
ankle
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Experimental results at knee energiesThe change of slope is observed in the
spectra of all EAS components
KASCADE
EAS-TOP
N
Ne
Eh
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Knee is due to the light primaries
Chemical composition gets heavieracross the knee
Position of the knee vary withprimary elemental groups (but relative abundaces heavily depend on the interaction model)
SYBILL
QGSJet
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• Knee is not related to a change in the interaction mechanism.
• Galactic SNR are observed as sources of TeV -rays
• Knee can be interpreted as the maximum energy for proton acceleration in SNR.
• Spectra of different elements change the slope at energy Eknee
Z = Z EKneep
• The SNR spectrum would extend to a maximum energy for iron Emax
Fe=26Emaxp
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Transition from Galactic to Extra-Galactic Radiation
• “Dip” Model– The spectrum is due to a single (proton dominated)
component.
– Ankle is due to the imprint of energy losses due to pair production in the CMB background.
– Transition correspond with the 2nd knee (E~4x1017 eV).
• “Mixed Composition” Model– Chemical composition similar to those known at “low
energy”
– Transition correspond to the ankle (E~3x1018 eV)
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The shape of the spectrum can be succesfully described by all models.Injection spectra are different
dip ~ 2.4-2.6 mixed ~ 2.2-2.3
Transition at the ankle requires Galactic sources that accelerates particles up to at least ~3x1018 eV (in the most optimisptic case)
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• Chemical composition measurements are crucial.
Allard et al. Astrop. Phys. 27 (2007) 61
mixeddip
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Experiments Operating in the 1016<E<1018 eV energy range
• KASCADE-Grande• IceTop• Tunka
• TALE• HEAT/Amiga
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S. Klepser@ECRS2008
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• Construction Completed in 2011• Ice Top resolutions (0°<<30°)
– Core position ~9m– Arrival direction ~1.5°– Energy (E>3PeV) ~16% in E
• Full Efficiency >1PeV
First results (ECRS 2008)
Primary Spectrum1015<E<1017 eV
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TUNKA 133Cherenkov ligth detector
20cm diameter PMTAngular aperture ≤45°Area ~1 km2
Full Efficiency E>2x1015 eVExpected Accuracy:15% energy ~25 g cm-2 Xmax
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KASCADE-Grande@Forschungszentrum Karlsruhe
Trigger efficiency in a fiducial area of 0.28 km2
HydrogenIronAll Elements
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DetectorDetector Detected Detected EAS EAS componentcomponent
Detection Detection TechniqueTechnique
DetectoDetector area r area (m(m22))
GrandeGrande Charged Charged particlesparticles
Plastic Plastic ScintillatorsScintillators
37x1037x10
PiccoloPiccolo Charged Charged particlesparticles
Plastic Plastic ScintillatorsScintillators
8x108x10
KASCADE KASCADE array e/array e/
Electrons, Electrons, Liquid Liquid ScintillatorsScintillators
490490
KASCADE KASCADE array array
MuonsMuons (E(Ethth=230 =230 MeV)MeV)
Plastic Plastic ScintillatorsScintillators
622622
MTDMTD Muons Muons (Tracking) (Tracking) (E(Ethth=800 =800 MeV)MeV)
Streamer TubesStreamer Tubes 4x1284x128
MWPCs/MWPCs/LSTsLSTs
Muons Muons (E(Ethth=2.4 =2.4 GeV)GeV)
Multiwire Multiwire Proportional Proportional ChambersChambers
3x1293x129
LOPES 30LOPES 30 RadioRadio Radio Antennas Radio Antennas (40-80 MHz)(40-80 MHz)
• Shower core and arrival
direction– Grande array
• Shower Size (Nch number of
charged particles)– Grande array
• Fit NKG like ldf
• Size (E>230 MeV)
– KASCADE array detectors• Fit Lagutin Function
• density (E>2400 MeV)
– MWPC
• density & direction (E>800 MeV)
– Streamer Tubes
KASCADE-Grande detectors & observables
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The resolution of the Grande array is obtained comparing the Grande event reconstruction with the one of the KASCADE array.
Similar results are obtained reconstructing simulated events.Covering a wider shower size range and the whole detector area.
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In each Shower size bin we obtain thedistribution of the difference betweenthe arrival directions measured by theGrande and by the KASCADE arrays
Fitting a Rayleigh distributionthe angular resolution ofthe Grande array is obtained
<0.7°
= arccos(cos(K)*cos(G)+sin(K)*sin(G)+cos(K-G))
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22 )()( GKGK yyxxr
core position resolution 5 m
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In each Shower Size bin we obtainthe distribution of the differencebetween the Shower Size determinedby the KASCADE and the Grande arrays
Kch
KchGch
N
NN
,
,,
scatter plot of Nch determined bythe KASCADE and by the Grandearrays
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Shower Size systematic differencerespect to KASCADE <5%
Grande Shower Sizereconstruction accuracy≤ 20%.
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Lateral distributions of charged particlesshowing the good performance of the array
saturation
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0°<<16.7°
16.7°<<23.4°
23.4°<<29.8°
29.8°<<35.1°
35.1°<<40°
1015 ev
1015 ev
1015 ev
1015 ev
1016 ev
1017 ev
1016 ev
1016 ev
1016 ev
1017 ev
1017 ev
1017 ev
Unfolding of 2-Dimensional shower size spectra, in different bin of zenith angle, will allow studies of energy&composition→ still improvements in systematics needed→ higher statistics
E>1017 eV4300 events
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Way to all particle Energy Spectrum:1) Constant Intensity Cut Method (Nch, N and S(500))
1) Integral spectra measured in different bins of zenith angle
2) For a given I(>NX) → NX()
Log Nch
Inte
gral
Flu
x I(
>N
ch)
3) Get Attenuation Curves
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A first study of the systematic (N) uncertainties has been performed
For E 1017 eV → E 22%
Energy Spectrum measurementsstarting from different observables.
Cross checks & Systematics
5) Nch,(ref) is converted to primary energy
Influence of: interaction models, MC statistics,slope used in the simulation
4) Nch,() → Nch,(ref)
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Way to all particle Energy Spectrum:2) Primary energy estimated event by event
• Nch (or N) as primary energy estimator
• Log(Nch/N) as mass and shower fluctuation estimator
From the bin to bin fluctuationsUncertainty ≤15% for E>1016 eV
from the ratio of reconstructed/true flux:systematic difference (different primaries)
<5% for E>1016 eV
log10(E)=a(k)log10(Nch)+b(k)
k=f(Nch/N,Nch)
H Fe
originalreconstructed
Log E(GeV)Log E(GeV)
Nu
mb
er o
f E
ven
ts
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First Results from KASCADE-Grande (ICRC 2007)
• Limits obtained with 1/3 of the available statistics are already significative.
• KASCADE-Grande results will play a relevant role in the evaluation of the anistropies in the knee region.
Anisotropy
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Conclusions• Wide interest in studying the 1016-1018 eV
energy range– Transition from Galactic to Extragalactic
primaries– Iron knee
• Soon relevant data from experiments with a resolution not yet reached in this energy range– KASCADE-Grande– IceTop
– Tunka, TALE, PAO