1. Latest Results from the KASCADE-Grande experiment
Andrea Chiavassa
Universita` degli Studi di Torino
4th Roma International Conference on Astroparticle Physic Roma, May 2013

2. Knee is due to the light component of cosmic rays
Change of slope of the heavy component observed at 8x1016 eV
Knee interpretation either by acceleration limit in galactic sources or by propagation effects
Not yet identified the transition to extragalactic primaries

3. KASCADE-Grande experiment
Karlsruher Institut
für Technologie

4. KASCADE-Grande detectors & observables
Grande array  cover an area of 0.5 km2, detecting EAS with high resolution
Detector
Detected EAS component
Detection Technique
Detector area (m2)
Grande
Charged particles
Plastic Scintillators
37x10
KASCADE array e/g
Electrons, g
Liquid Scintillators
490
KASCADE array m
Muons
(Emth=230 MeV)
622
MTD
Muons (Tracking) (Emth=800 MeV)
Streamer Tubes
4x128
Shower core and arrival
direction
Shower Size (Nch number of
charged particles)
Grande array
m Size (Em>230 MeV)
KASCADE array m detectors
m density & direction (Em>800 MeV)
Streamer Tubes

5. KASCADE-Grande accuracies with a subsample
of common events KASCADE + Grande
100% efficiency
■ KASCADE stations
■ Grande stations
Apel et al. NIMA 620 (2010)

6. All particle energy spectrum
Combination of Nch and Nm
Five different angular bins
k parameter evaluates chemical composition, used as a weight in the expression correlating Nch and E
Based on QGSJet II-02
Astroparticle Physics 36, (2012) 183

7. Energy spectra measured in the five angular bins
Spectrum cannot be described by a single power law
Hardening above 1016 eV
Steepening close to 1017 eV
significance 2.1s
Comparison of the KG spectrum
with different experiments
Astroparticle Physics 36, (2012) 183

8. Approach to Chemical Composition

9. Unfolding
Analysis objective is to compute the spectra of NNucl mass groups.
Ni number of events expected in the bin :
pn is obtained from full EAS and detector simulation (based on QGSJet II)
sn EAS development fluctuations
rn, reconstruction resolution, including systematic reconstruction effects
en, trigger efficiency

10. QGSJet II-02
Spectra of five mass groups obtained applying the unfolding technique to the KASCADE-Grande data. Only the heavier mass group spectrum (Fe) shows a significant steepening

11. Spectra agree well with those obtained applying the unfolding technique to KASCADE data.
Both data sets are analyzed with the QGSJetII-02 hadronic interaction model

12. Event by event separation in two mass groups by the Nch/Nm ratio
Two different ways of taking into account the EAS attenuation in atmosphere

13. YCIC is constant with E
(E > full efficiency)
For a specific hadronic interaction model
YCIC increases with primary mass
choice of YCIC  choice of a primary mass
For a particular primary element
YCIC increases when calculated by a model generating EAS with higher Nm
 for the same primary mass the choice of YCIC is shifted

14. Energy spectra of the samples obtained by an event selection based on the k parameter
Spectrum of the electron
poor sample 
k>(kC+kSi)/2
 steepening
observed with increased
significance  3.5s
Spectrum of electron rich events  can be described by a single power law  hints of a hardening above 1017 eV
g1 = -2.76±0.02
g2 = -3.24±0.05
Eb = ±0.04
Phys. Rev. Lett. 107 (2011)

15. Steepening observed at the same energy independently of the cut choice
Spectra obtained with the two different strategies agree
Steepening observed at the same energy independently of the cut choice
The steepening of the electron poor sample is enhanced cutting at higher YCIC values
YCIC event selection
Phys. Rev. Lett. 107 (2011)

16. Investigations of the electron rich sample
Statistics increased by 36% adding new data sets and increasing the effective area
To enhance possible structures of the electron rich sample 
k < (kC+kHe)/2
Phys. Rev. D 87, (R) (2013)

17. Spectra obtained enhancing the electron-rich event selection show a clearer hardening above 1017 eV
Phys. Rev. D 87, (R) (2013)

18. g1 = -3.25±0.05
g2 = -2.79±0.08
Eb = ±0.08
Nmeas = 579
Nexp = 467
P(N>Nmeas)≈7.23x10-09
5.8s significance
Phys. Rev. D 87, (R) (2013)

19. Conclusions Eb(light) ≠ Eb(heavy) g1(light) = g2(heavy)
KASCADE-Grande data taking stopped in November 2012.
All particle spectrum:
Hardening ~1016 eV
Steepening ~8x1016 eV
Steepening of the heavy primaries spectrum at ±0.04 eV. Slope index changes from 2.76±0.02 to 3.24±0.05
Hardening of the light primaries spectrum at ±0.08 eV. Slope index changes from 3.25±0.05 to 2.79±0.08
Eb(light) ≠ Eb(heavy)
g1(light) = g2(heavy)
g2(light) ≈ 2.7