Contributions of the University of Bucharest to the study of high energy cosmic rays in the...

Contributions of the University of Bucharest to the study of

high energy cosmic rays in the framework of the

KASCADE-Grande experimentOctavian Sima

Faculty of Pysics, University of Bucharest

Astroparticles in Romania, 2009

Cosmic rays

• Radiation environment

• Cosmogenic radionuclides

• Physics:– Discovery of elementary particles

– Study of high energy interactions

– What is the source of high energy cosmic rays?

– What is the mechanism of acceleration?

– How do they propagate to the Earth?

– Can they reveal unknown features of high energy interactions?

– Can they provide information on the early stages of the Universe?

– …

– …


High energy cosmic raysDirect measurement:baloons, satellites

Indirect measurements based on Extensive Air Showers (EAS)


KASCADE-Grande:measurements of air showers with energy 100 TeV - 1 EeV

Grande Array

Piccolo ArrayKASCADE

Lopes

KASCADE-Grande


Standard shower reconstruction: KRETA• calibrated detector signal converted to charged particle density

using LECF (mean energy deposit per charged particle)• muon density obtained by fitting the data from KASCADE

muon detectors• electron density obtained by fitting charged particle density

and muon density extrapolated from KASCADE toGrande detectors using specific LDFs

• primary energy evaluated using the muon and the electronsize of the shower

• primary particle identification based on the correlation of the electron size and the muon size of the shower

LECF, LDF, energy estimator, mass estimator obtained fromthe analysis of simulated showers using CORSIKA


In standard analysis azimuthal symmetry of the quantitiesas a function of the position around the shower coreis assumed, e.g:

• LECF = function(r), r – radial coordinate, independent of • LDF = function(r)

LDF for muons and electrons very important for shower reconstruction, for obtaining information on energy spectrum and mass composition


Contributions of Faculty of Physics

Refined analysis and reconstruction of showers

Tools developed:

SHOWREC & STATSHW– tools for shower reconstruction

COMPLDIST – tool for shower analysis

Examples:

• Reconstruction of CORSIKA showers, study of LDFs

• Restoring the azymuthal symmetry of LDFs

• Fast procedure for energy deposition in detectors

• Realistic LEFC

• Muon charge ratio

S600

S100


Azimuthal asymmetry of LDF

Origin of the asymmetry:• shower development (“attenuation”)• geometry effects• geomagnetic field

O LateFast

S

Information from the KASCADE-Grande detectors does not allow a complete integration of the lateral density function(LDF) around the shower core => deviations from azimuthal symmetry may be important

- especially at large radial distances (S500)

- muon density is reconstructed from KASCADE array (located in the NE corner of the Grande area)


CORSIKA simulationwithout the Earth’smagnetic field

=> Projection ontothe normal planereduces the asymmetry,but does not eliminate it

=> The simple modelnot adequate


Electrons:Reconstructed LDFin the normal plane

Method 1: orthogonal projection

Method 2: along particle momentum

Method 3: triangulation based on arrival time

Differences betweenprojection methods

Important asymmetry


Evaluation of LECF:• CORSIKA simulations provide the characteristics of the

particles that hit the detectors• GEANT simulations give the energy deposit in each

detector

Our approach – GEANT distributions fitted with simple functions, that can be sampled by Monte Carlo

=> much faster

Possible to include azimuthal dependence

obtain the map of energy deposit


GEANT versus fast procedurefor electron energy depositionin Grande detectors

Map of the muon energy depositin Grande detectors


Map of the mean energydeposit per charged particle

p, 3.16 1017 eV, =45o from North

Fe, 5.62 1017 eV, =45o from North

Muon charge ratio for EAS muons (p E=1 PeV, =45)Left: shower incident from NRight: shower incident from South


Conclusions

Procedures for a detailed analysis of Extensive Air Showers have been developed

SHOWREC, STATSHW, COMPLDISTThe procedures have been applied for shower analysis and reconstructionBoth simulated showers and experimental data can be processedApplications:

Lateral Energy Correction FunctionsLateral Density DistributionsS(500)Muon Charge Ratio

Contributions of the University of Bucharest to the study of high energy cosmic rays in the...

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