Status of Cosmic Rays Physics at the Knee
Andrea ChiavassaUniversità and INFN Torino
NOW 2006Otranto 9-16 September 2006
1 particle m-2 s-1
Knee1 particle m-2 year-1
Ankle1 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 NCerenkov Light Xmax
HEGRA 790 Scintillators Ne
Cerenkov Light N Xmax
EAS-TOP 810 Scintillators Ne
Streamer Tubes N>1 GeV Nh
Cerenkov Light N
KASCADE 1020 Scintillators Ne N (E>230 MeV)
Calorimetr Nh Eh
MWPC N (E>2400 MeV)
TIBET AS 606 Scintillators Ne
Emulsion -families
TUNKA 25 950 Cerenkov Light N Xmax
The spectra of all the components of EAS show the “Knee”: Ne, N, Eh
KASCADE
EAS-TOP
N
Ne
Eh
Spectra of “light” and “heavy” elements of Cosmic Rays
KASCADEOnly the spectrum obtained using “electron rich” events shows the change of slope
Energy Spectrum of Single Elements
Spectra of light elements show the kneePosition of the knee vary with primary elemental groupEknee Z or Eknee A ??Knee of heavy elements out of the experimental range
Risulats depend heavily on the interaction model used.
MACRO EAS-TOPL = p + HeH = Mg + Fe
Macro EAS TOP
Em shower
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 events1996-1999 data177 events
Tibet AS experiment
H SpectrumTibet AS data agree with:RUNJOBKASCADE (Sibyll)
HE Spectrum =“HE+H”-”H”Agree with RUNJOBLower than:JACEE, KASCADE
Conclusion: Composition already heavy at the knee
Future evolutions from measurements in the 1016 – 1018 eV energy range
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-GrandeICETOP/ICECUBE
KASCADE-Grande Experiment @ FZK KarlsruheKASCADE-Grande Experiment @ FZK Karlsruhe
KASCADE
KASCADE e/ detectors Grande array37 Scintillator stations (10 m2 each)Total Surface 0.5 km2
N (> 1018 eV) ~ 250 events(3 y data taking)
First results from the KASCADE-Grande Experiment
Unfolding analysis from 2 dimensional spectra is possible
All angular bins show the same energy spectrum
Study of systematics still to be improved!!!!!!
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 AS)
• 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 (inel, K, ......)