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, ......)