Cosmic Rays from to eV. Open Problem and Experimental Results. (KASCADE-Grande view) Very High Energy Phenomena in the Universe XLIV th Rencontres de Moriond La Thuile 1-8 February 2009 Andrea Chiavassa Università di Torino

Energy range covered in this talk 2nd knee Iron knee?? Transition from Galactic to ExtraGalactic Cosmic Rays?? knee 2nd knee ankle

Experimental results at knee energies The change of slope is observed in the spectra of all EAS components KASCADE EAS-TOP NN Ne EhEh

Knee is due to the light primaries Chemical composition gets heavier across the knee Position of the knee vary with primary elemental groups (but relative abundaces heavily depend on the interaction model) SYBILL QGSJet

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 E knee Z = Z E Knee p The SNR spectrum would extend to a maximum energy for iron E max Fe =26E max p

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~4x10 17 eV). “Mixed Composition” Model –Chemical composition similar to those known at “low energy” –Transition correspond to the ankle (E~3x10 18 eV)

The shape of the spectrum can be succesfully described by all models. Injection spectra are different dip   ~ mixed   ~ Transition at the ankle requires Galactic sources that accelerates particles up to at least ~3x10 18 eV (in the most optimisptic case)

Chemical composition measurements are crucial. Allard et al. Astrop. Phys. 27 (2007) 61 mixed dip

Experiments Operating in the <E<10 18 eV energy range KASCADE-Grande IceTop Tunka TALE HEAT/Amiga

S.

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 Spectrum <E<10 17 eV

TUNKA 133 Cherenkov ligth detector 20cm diameter PMT Angular aperture ≤ 45° Area ~ 1 km 2 Full Efficiency E>2x10 15 eV Expected Accuracy: 15% energy ~25 g cm -2 X max

Karlsruhe Trigger efficiency in a fiducial area of 0.28 km 2 Hydrogen Iron All Elements

Detector Detected EAS component Detection Technique Detecto r area (m 2 ) Grande Charged particles Plastic Scintillators 37x10 Piccolo Charged particles Plastic Scintillators 8x10 KASCADE array e/  Electrons,  Liquid Scintillators 490 KASCADE array  Muons (E  th =230 MeV) (E  th =230 MeV) Plastic Scintillators 622 MTD Muons (Tracking) (E  th =800 MeV) Streamer Tubes 4x128 MWPCs/LS Ts Muons (E  th =2.4 GeV) Multiwire Proportional Chambers 3x129 LOPES 30 Radio Radio Antennas (40-80 MHz) Shower core and arrival direction –Grande array Shower Size (N ch 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

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.

In each Shower size bin we obtain the distribution of the difference between the arrival directions measured by the Grande and by the KASCADE arrays Fitting a Rayleigh distribution the angular resolution of the Grande array is obtained  <0.7°  = arccos(cos(  K )*cos(  G )+sin(  K )*sin(  G )+cos(  K -  G ))

core position resolution   5 m

In each Shower Size bin we obtain the distribution of the difference between the Shower Size determined by the KASCADE and the Grande arrays scatter plot of N ch determined by the KASCADE and by the Grande arrays

Shower Size systematic difference respect to KASCADE <5% Grande Shower Size reconstruction accuracy ≤ 20%.

Lateral distributions of charged particles showing the good performance of the array saturation

0°<  <16.7° 16.7°<  <23.4° 23.4°<  <29.8° 29.8°<  <35.1° 35.1°<  <40° ev ev ev ev 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>10 17 eV  4300 events

Way to all particle Energy Spectrum: 1) Constant Intensity Cut Method (N ch, N  and S(500)) 1)Integral spectra measured in different bins of zenith angle 2) For a given I(>N X ) → N X (  ) Log N ch Integral Flux I(>N ch ) 3) Get Attenuation Curves

A first study of the systematic (N  ) uncertainties has been performed For E  eV →  E  22% Energy Spectrum measurements starting from different observables. Cross checks & Systematics 5) N ch,  (  ref ) is converted to primary energy Influence of: interaction models, MC statistics, slope used in the simulation 4) N ch,  (  ) → N ch,  (  ref )

Way to all particle Energy Spectrum: 2) Primary energy estimated event by event N ch (or N  ) as primary energy estimator Log(N ch /N  ) as mass and shower fluctuation estimator From the bin to bin fluctuations Uncertainty ≤15% for E>10 16 eV from the ratio of reconstructed/true flux: systematic difference (different primaries) eV log 10 (E)=a(k)  log 10 (N ch )+b(k) k=f(N ch /N ,N ch ) HFe original reconstructed Log E(GeV) Number of Events

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

Conclusions Wide interest in studying the 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