Cosmic Rays from 10 16 to 10 18 eV. Open Problem and Experimental Results. (KASCADE-Grande view)

1. Cosmic Rays from 1016 to 1018 eV. Open Problem and Experimental Results.(KASCADE-Grande view) Very High Energy Phenomena in the Universe XLIVth Rencontres de Moriond La Thuile 1-8 February 2009 Andrea Chiavassa Università di Torino

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

3. Experimental results at knee energiesThe change of slope is observed in the spectra of all EAS components EAS-TOP SEh KASCADE Nm Ne

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

5. Knee is not related to a change in the interaction mechanism. • Galactic SNR are observed as sources of TeV g-rays • Knee can be interpreted as the maximum energy for proton acceleration in SNR. • Spectra of different elements change the slope at energy EkneeZ = Z EKneep • The SNR spectrum would extend to a maximum energy for iron EmaxFe=26Emaxp

6. 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)

7. The shape of the spectrum can be succesfully described by all models. Injection spectra are different dip a~ 2.4-2.6 mixed a~ 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)

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

9. Experiments Operating in the 1016<E<1018 eV energy range • KASCADE-Grande • IceTop • Tunka • TALE • HEAT/Amiga

10. S. Klepser@ECRS2008

11. Construction Completed in 2011 • Ice Top resolutions (0°<q<30°) • Core position ~9m • Arrival direction ~1.5° • Energy (E>3PeV) ~16% in E • Full Efficiency >1PeV First results (ECRS 2008) Primary Spectrum 1015<E<1017 eV

12. TUNKA 133 Cherenkov ligth detector 20cm diameter PMT Angular aperture ≤45° Area ~1 km2 Full Efficiency E>2x1015 eV Expected Accuracy: 15% energy ~25 g cm-2 Xmax

13. KASCADE-Grande @Forschungszentrum Karlsruhe Hydrogen Iron All Elements Trigger efficiency in a fiducial area of 0.28 km2

14. KASCADE-Grande detectors & observables • Shower core and arrival direction • Grande array • Shower Size (Nch number of charged particles) • Grande array • Fit NKG like ldf • m Size (Em>230 MeV) • KASCADE array m detectors • Fit Lagutin Function • m density (Em>2400 MeV) • MWPC • m density & direction (Em>800 MeV) • Streamer Tubes

15. 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.

16. 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 DY = arccos(cos(qK)*cos(qG)+sin(qK)*sin(qG)+cos(FK-FG)) • Fitting a Rayleigh distribution • the angular resolution of • the Grande array is obtained • <0.7°

17. core position resolution s 5 m

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

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

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

21. 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 eV 4300 events 0°<q<16.7° 1017 ev 1017 ev 1016 ev 1016 ev 1015 ev 1015 ev 29.8°<q<35.1° 16.7°<q<23.4° 1017 ev 1017 ev 1016 ev 1016 ev 1015 ev 1015 ev 35.1°<q<40° 23.4°<q<29.8°

22. Way to all particle Energy Spectrum:1) Constant Intensity Cut Method (Nch, Nm and S(500)) Integral Flux I(>Nch) Log Nch • Integral spectra measured in • different bins of zenith angle • 2) For a given I(>NX) → NX(q) 3) Get Attenuation Curves

23. 4) Nch,m(q) → Nch,m(qref) 5) Nch,m(qref) is converted to primary energy Influence of: interaction models, MC statistics, slope used in the simulation Energy Spectrum measurements starting from different observables. Cross checks & Systematics A first study of the systematic (Nm) uncertainties has been performed For E 1017 eV → DE 22%

24. 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 log10(E)=a(k)log10(Nch)+b(k) k=f(Nch/N,Nch) H Fe Number of Events from the ratio of reconstructed/true flux: systematic difference (different primaries) <5% for E>1016 eV original reconstructed Log E(GeV) Log E(GeV) From the bin to bin fluctuations Uncertainty ≤15% for E>1016 eV

25. First Results from KASCADE-Grande (ICRC 2007) Anisotropy • 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.

26. 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