Transcript Cosmic Rays from 1016 to 1018 eV. Open Problem and

Cosmic Rays from 1016 to 1018 eV.
Open Problem and Experimental
Results.
(KASCADE-Grande view)
Very High Energy Phenomena in the Universe
XLIVth Rencontres de Moriond
La Thuile 1-8 February 2009
Andrea Chiavassa
Università di Torino
2nd knee
knee
ankle
Energy range covered in this talk
2nd knee
Iron knee??
Transition from Galactic to
ExtraGalactic Cosmic Rays??
Experimental results at knee energies
The change of slope is observed in the
spectra of all EAS components
EAS-TOP
SEh
KASCADE
Nm
Ne
Knee is due to the light primaries
Chemical composition gets heavier
across the knee
SYBILL
QGSJet
Position of the knee vary with
primary elemental groups
(but relative abundaces heavily depend on the interaction model)
• Knee is not related to a change in the
interaction mechanism.
• Galactic SNR are observed as sources of TeV grays
• Knee can be interpreted as the maximum energy
for proton acceleration in SNR.
• Spectra of different elements change the slope
at energy EkneeZ = Z EKneep
• The SNR spectrum would extend to a maximum
energy for iron EmaxFe=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 a ~ 2.4-2.6 mixed a ~ 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.
mixed
dip
Allard et al. Astrop. Phys. 27 (2007) 61
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°<q<30°)
– Core position ~9m
– Arrival direction ~1.5°
– Energy (E>3PeV) ~16% in E
• Full Efficiency >1PeV
First results (ECRS 2008)
Primary Spectrum
1015<E<1017 eV
TUNKA 133
Cherenkov ligth detector
20cm diameter PMT
Angular aperture ≤45°
Area ~1 km2
Full Efficiency E>2x1015 eV
Expected Accuracy:
15% energy
~25 g cm-2 Xmax
KASCADE-Grande
@Forschungszentrum Karlsruhe
Hydrogen
Iron
All Elements
Trigger efficiency in a
fiducial area of 0.28 km2
KASCADE-Grande detectors & observables
Detector
Detected
EAS
component
Detection
Technique
Detecto
r area
(m2)
Grande
Charged
particles
Plastic
Scintillators
37x10
Piccolo
Charged
particles
Plastic
Scintillators
8x10
KASCADE
array e/g
Electrons, g
Liquid
Scintillators
490
KASCADE
array m
Muons
(Emth=230
MeV)
Plastic
Scintillators
622
MTD
Muons
(Tracking)
(Emth=800
MeV)
Streamer Tubes
4x128
MWPCs/LS
Ts
Muons
(Emth=2.4
GeV)
Multiwire
Proportional
Chambers
LOPES 30
Radio
Radio Antennas
(40-80 MHz)
• Shower core and arrival
direction
– Grande array
• Shower Size (Nch number of
charged particles)
– Grande array
•
•
m Size (Em>230 MeV)
– KASCADE array m detectors
•
3x129
•
•
Fit NKG like ldf
Fit Lagutin Function
m density (Em>2400 MeV)
– MWPC
m density & direction
(Em>800 MeV)
– Streamer Tubes
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 the
distribution of the difference between
the arrival directions measured by the
Grande and by the KASCADE arrays
DY = arccos(cos(qK)*cos(qG)+sin(qK)*sin(qG)+cos(FK-FG))
Fitting a Rayleigh distribution
the angular resolution of
the Grande array is obtained
<0.7°
Dr  ( xK  xG ) 2  ( y K  yG ) 2
core position
resolution
5m
scatter plot of Nch determined by
the KASCADE and by the Grande
arrays
In each Shower Size bin we obtain
the distribution of the difference
between the Shower Size determined
by the KASCADE and the Grande arrays
N ch,G  N ch, K
N ch, K
Shower Size systematic difference
respect to KASCADE <5%
Grande Shower Size
reconstruction accuracy
≤ 20%.
Lateral distributions of charged particles
showing the good performance of the array
saturation
0°<q<16.7°
Unfolding of 2-Dimensional shower size
spectra, in different bin of zenith angle,
will allow studies of energy&composition
→ still improvements in systematics
needed
E>1017 eV
→ higher statistics
4300 events
1017 ev
1017 ev
1016 ev
1016 ev
1015 ev
1015 ev
29.8°<q<35.1°
16.7°<q<23.4°
1017 ev
1016
1017 ev
ev
1016 ev
1015 ev
1015 ev
23.4°<q<29.8°
35.1°<q<40°
Way to all particle Energy Spectrum:
Integral Flux I(>Nch)
1) Constant Intensity Cut Method (Nch, Nm and S(500))
Log Nch
1) Integral spectra measured in
different bins of zenith angle
2) For a given I(>NX) → NX(q)
3) Get Attenuation Curves
4) Nch,m(q) → Nch,m(qref)
5) Nch,m(qref) is converted to primary energy
Influence of: interaction models, MC statistics,
slope used in the simulation
Energy Spectrum measurements
starting from different observables.
Cross checks & Systematics
A first study of the systematic (Nm)
uncertainties has been performed
For E 1017 eV → DE 22%
Way to all particle Energy Spectrum:
2) Primary energy estimated event by event
• Nch (or Nm) as primary
energy estimator
• Log(Nch/Nm) as mass
and shower fluctuation
estimator
k=f(Nch/Nm,Nch)
H
Number of Events
from the ratio of
reconstructed/true flux:
systematic difference
(different primaries)
<5% for E>1016 eV
log10(E)=a(k)log10(Nch)+b(k)
Fe
original
reconstructed
Log E(GeV)
From the bin to bin fluctuations
Uncertainty ≤15% for E>1016 eV
Log E(GeV)
First Results from KASCADE-Grande (ICRC 2007)
Anisotropy
• 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.
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