Status of Cosmic Rays Physics
at the Knee
Andrea Chiavassa
Università and INFN Torino
NOW 2006
Otranto 9-16 September 2006
1 particle m-2 s-1
Knee
1 particle m-2 year-1
Ankle
1 particle km-2 year-1
Hypotesis on the origin of the Knee
• Reach of maximum energy at the
acceleration in Galactic Sources?
SNR (Eknee  Z)
Cannonball  (Eknee  A)
• Diffusion: Escape of particles from
Galactic Magnetic fields? (Eknee  Z)
• Unknown effects of interaction in the
development of Extensive Air Showers?
(Eknee  A)
Measurement that can separate
different hypotesis
• Chemical Composition of CR
• Anisotropy
• Single Element Spectra
EAS Experiments
• Measurements of different components of EAS to
determine: Energy, Mass, Arrival Direction
• High Statistics 
• Data Interpretation strictly connected with MC 
Experiment
X (g cm-2)
CASA-MIA
BLANCA
870
Scintillators Ne Nm
Cerenkov Light Xmax
HEGRA
790
Scintillators Ne
Cerenkov Light Ng Xmax
EAS-TOP
810
Scintillators Ne
Streamer Tubes Nm (Em>1 GeV) Nh
Cerenkov Light Ng
KASCADE
1020
Scintillators Ne Nm (Em>230 MeV)
Calorimetr Nh Eh
MWPC Nm (Em>2400 MeV)
TIBET ASg
606
Scintillators Ne
Emulsion g-families
TUNKA 25
950
Cerenkov Light Ng Xmax
The spectra of all the components of EAS
show the “Knee”: Ne, Nm, SEh
KASCADE
SEh
Nm
Ne
EAS-TOP
Spectra of “light” and “heavy” elements of
Cosmic Rays
KASCADE
Only the spectrum obtained using
“electron rich” events shows the
change of slope
Energy Spectrum of Single Elements
Spectra of light elements show the knee
Position of the knee vary with primary elemental group
Eknee  Z or Eknee  A ??
Knee of heavy elements out of the experimental range
Risulats depend heavily on the interaction model used.
MACRO EAS-TOP
L = p + He
H = Mg + Fe
Em shower
Macro EAS TOP
Tibet ASg experiment
4300 m a.s.l. 606 g cm-2
221 counters (15m grid)
+ emulsion chambers (80 m2)
+ burst detector (80 m2 below EC)
Simulations show that detector is almost blind to heavy fragments
MC assumes knee at E=1.5•1014•Z (below energy range of experiment)
Neural Nets analysis allow to select H or HE events
1996-1999 data
177 events
H Spectrum
Tibet ASg data agree with:
RUNJOB
KASCADE (Sibyll)
HE Spectrum =“HE+H”-”H”
Agree with RUNJOB
Lower than:JACEE, KASCADE
Conclusion: Composition already heavy at the knee
Future evolutions from measurements in the
1016 – 1018 eV energy range
KASCADE-Grande
ICETOP/ICECUBE
If : Ek,Z = Z * Ek,1
SEARCH FOR IRON “KNEE”
AT ~ 1017 eV
PRIMARY COMPOSITION
STUDY OF C.R.
INTERACTIONS AT UHE
TRANSITION GALACTIC –
EXTRAGALACTIC C.R.?
KASCADE-Grande Experiment @ FZK Karlsruhe
KASCADE
N (> 1018 eV) ~ 250 events
(3 y data taking)
KASCADE e/g + m detectors
Grande array
37 Scintillator stations (10 m2 each)
Total Surface 0.5 km2
First results from the
KASCADE-Grande Experiment
Study of systematics still
to be improved!!!!!!
All angular bins show
the same energy spectrum
Unfolding analysis from
2 dimensional spectra is possible
Main Results & Future Developments
1015 eV < E < 1018 eV
• Knee observed in the spectra of all EAS components
• Knee caused by light elements (don’t forget Tibet ASg)
• Primary chemical composition evolves, above the knee,
towards heavier elements
• Still differences in the results obtained at different altitudes
and with different techniques  better understanding of
primary interactions!!! (LHC!)
• Anisotropy
• Future Developments:
– Search for the “knee” of heavy elements
– Detailed study of the 1016 – 1018 eV energy range
– Interaction Models (sinel, K, m......)