Cosmic Rays from 1016 to 1018 eV. Open Problem and Experimental Results.

(KASCADE-Grande view)

Very High Energy Phenomena in the UniverseXLIVth Rencontres de Moriond

La Thuile 1-8 February 2009

Andrea ChiavassaUniversità di Torino

Energy range covered in this talk2nd kneeIron knee??Transition from Galactic to ExtraGalactic Cosmic Rays??

knee

2nd knee

ankle

Experimental results at knee energiesThe change of slope is observed in the

spectra of all EAS components

KASCADE

EAS-TOP

N

Ne

Eh

Knee is due to the light primaries

Chemical composition gets heavieracross the knee

Position of the knee vary withprimary elemental groups (but relative abundaces heavily depend on the interaction model)

SYBILL

QGSJet

• Knee is not related to a change in the interaction mechanism.

• Galactic SNR are observed as sources of TeV -rays

• Knee can be interpreted as the maximum energy for proton acceleration in SNR.

• Spectra of different elements change the slope at energy Eknee

Z = Z EKneep

• The SNR spectrum would extend to a maximum energy for iron Emax

Fe=26Emaxp

Transition from Galactic to Extra-Galactic Radiation

• “Dip” Model– The spectrum is due to a single (proton dominated)

component.

– Ankle is due to the imprint of energy losses due to pair production in the CMB background.

– Transition correspond with the 2nd knee (E~4x1017 eV).

• “Mixed Composition” Model– Chemical composition similar to those known at “low

energy”

– Transition correspond to the ankle (E~3x1018 eV)

The shape of the spectrum can be succesfully described by all models.Injection spectra are different

dip ~ 2.4-2.6 mixed ~ 2.2-2.3

Transition at the ankle requires Galactic sources that accelerates particles up to at least ~3x1018 eV (in the most optimisptic case)

• Chemical composition measurements are crucial.

Allard et al. Astrop. Phys. 27 (2007) 61

mixeddip

Experiments Operating in the 1016<E<1018 eV energy range

• KASCADE-Grande• IceTop• Tunka

• TALE• HEAT/Amiga

S. Klepser@ECRS2008

• Construction Completed in 2011• Ice Top resolutions (0°<<30°)

– Core position ~9m– Arrival direction ~1.5°– Energy (E>3PeV) ~16% in E

• Full Efficiency >1PeV

First results (ECRS 2008)

Primary Spectrum1015<E<1017 eV

TUNKA 133Cherenkov ligth detector

20cm diameter PMTAngular aperture ≤45°Area ~1 km2

Full Efficiency E>2x1015 eVExpected Accuracy:15% energy ~25 g cm-2 Xmax

KASCADE-Grande@Forschungszentrum Karlsruhe

Trigger efficiency in a fiducial area of 0.28 km2

HydrogenIronAll Elements

DetectorDetector Detected Detected EAS EAS componentcomponent

Detection Detection TechniqueTechnique

DetectoDetector area r area (m(m22))

GrandeGrande Charged Charged particlesparticles

Plastic Plastic ScintillatorsScintillators

37x1037x10

PiccoloPiccolo Charged Charged particlesparticles

Plastic Plastic ScintillatorsScintillators

8x108x10

KASCADE KASCADE array e/array e/

Electrons, Electrons, Liquid Liquid ScintillatorsScintillators

490490

KASCADE KASCADE array array

MuonsMuons (E(Ethth=230 =230 MeV)MeV)

Plastic Plastic ScintillatorsScintillators

622622

MTDMTD Muons Muons (Tracking) (Tracking) (E(Ethth=800 =800 MeV)MeV)

Streamer TubesStreamer Tubes 4x1284x128

MWPCs/MWPCs/LSTsLSTs

Muons Muons (E(Ethth=2.4 =2.4 GeV)GeV)

Multiwire Multiwire Proportional Proportional ChambersChambers

3x1293x129

LOPES 30LOPES 30 RadioRadio Radio Antennas Radio Antennas (40-80 MHz)(40-80 MHz)

 

• Shower core and arrival

direction– Grande array

• Shower Size (Nch number of

charged particles)– Grande array

• Fit NKG like ldf

• Size (E>230 MeV)

– KASCADE array detectors• Fit Lagutin Function

• density (E>2400 MeV)

– MWPC

• density & direction (E>800 MeV)

– Streamer Tubes

KASCADE-Grande detectors & observables

The resolution of the Grande array is obtained comparing the Grande event reconstruction with the one of the KASCADE array.

Similar results are obtained reconstructing simulated events.Covering a wider shower size range and the whole detector area.

In each Shower size bin we obtain thedistribution of the difference betweenthe arrival directions measured by theGrande and by the KASCADE arrays

Fitting a Rayleigh distributionthe angular resolution ofthe Grande array is obtained

<0.7°

= arccos(cos(K)*cos(G)+sin(K)*sin(G)+cos(K-G))

22 )()( GKGK yyxxr

core position resolution 5 m

In each Shower Size bin we obtainthe distribution of the differencebetween the Shower Size determinedby the KASCADE and the Grande arrays

Kch

KchGch

N

NN

,

,,

scatter plot of Nch determined bythe KASCADE and by the Grandearrays

Shower Size systematic differencerespect to KASCADE <5%

Grande Shower Sizereconstruction accuracy≤ 20%.

Lateral distributions of charged particlesshowing the good performance of the array

saturation

0°<<16.7°

16.7°<<23.4°

23.4°<<29.8°

29.8°<<35.1°

35.1°<<40°

1015 ev

1015 ev

1015 ev

1015 ev

1016 ev

1017 ev

1016 ev

1016 ev

1016 ev

1017 ev

1017 ev

1017 ev

Unfolding of 2-Dimensional shower size spectra, in different bin of zenith angle, will allow studies of energy&composition→ still improvements in systematics needed→ higher statistics

E>1017 eV4300 events

Way to all particle Energy Spectrum:1) Constant Intensity Cut Method (Nch, N and S(500))

1) Integral spectra measured in different bins of zenith angle

2) For a given I(>NX) → NX()

Log Nch

Inte

gral

Flu

x I(

>N

ch)

3) Get Attenuation Curves

A first study of the systematic (N) uncertainties has been performed

For E 1017 eV → E 22%

Energy Spectrum measurementsstarting from different observables.

Cross checks & Systematics

5) Nch,(ref) is converted to primary energy

Influence of: interaction models, MC statistics,slope used in the simulation

4) Nch,() → Nch,(ref)

Way to all particle Energy Spectrum:2) Primary energy estimated event by event

• Nch (or N) as primary energy estimator

• Log(Nch/N) as mass and shower fluctuation estimator

From the bin to bin fluctuationsUncertainty ≤15% for E>1016 eV

from the ratio of reconstructed/true flux:systematic difference (different primaries)

<5% for E>1016 eV

log10(E)=a(k)log10(Nch)+b(k)

k=f(Nch/N,Nch)

H Fe

originalreconstructed

Log E(GeV)Log E(GeV)

Nu

mb

er o

f E

ven

ts

First Results from KASCADE-Grande (ICRC 2007)

• Limits obtained with 1/3 of the available statistics are already significative.

• KASCADE-Grande results will play a relevant role in the evaluation of the anistropies in the knee region.

Anisotropy

Conclusions• Wide interest in studying the 1016-1018 eV

energy range– Transition from Galactic to Extragalactic

primaries– Iron knee

• Soon relevant data from experiments with a resolution not yet reached in this energy range– KASCADE-Grande– IceTop

– Tunka, TALE, PAO