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SLIDE 1

Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande

Fabiana Cossavella 27 October 2009

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 1

SLIDE 2

Outline

overview of the KASCADE-Grande experiment
air shower measurement and reconstruction
cosmic ray spectrum
composition study

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 2

SLIDE 3

Cosmic Ray Energy Spectrum

Energy (GeV)

4

10

5

10

6

10

7

10

8

10

9

10

11

10

12

10

)

1.5

eV

1

sr

1

s

2

J(E) (m

2.5

E

13

10

14

10

15

10

16

10

17

10

18

10

19

10

KASCADE-Grande

direct data

Akeno AGASA HiRes I HiRes II AUGER 2008 (PRL)

EAS-TOP KASCADE (QGSJET 01) µ KASCADE-Grande (QGSJET II) Nch-N

break in the single elemental spectra at E ∝ Z · Eknee

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 3

SLIDE 4

Detection: Extensive Air Showers

interaction primary-air → mainly

π-mesons

secondary products interact

(hadrons) or decay (muons, electrons)

particles reach ground in a shower

disc

longitudinal profile → N particles as function of the

atmospheric depth

lateral profile → distribution at ground of the shower particles

as a function of the distance from the shower axis

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 4

SLIDE 5

Different primaries

dominated by electromagnetic component

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 5

SLIDE 6

Different primaries

Nµ/Ne larger as compared to proton

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 5

SLIDE 7

The KASCADE Experiment

Physics Observables

electron
gammas
muons
hadrons

The detectors

Array stations: liquid scintillator for e/γ detection and plastic

scintillator for µ detection above 230 MeV

Muon Tracking Detector for Eµ ≥ 800 MeV
MWPC/LSTs for muon detection above 2.4 GeV
Calorimeter, for hadron detection

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 6

SLIDE 8

KASCADE-Grande

KASCADE extension to 700 × 700 m2

energy spectrum and composition from

1016 eV to 1018 eV

galactic to extragalactic transition?
Testing hadronic interaction models
iron knee ?
origin of the knee ?
Anisotropies

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 7

SLIDE 9

KASCADE-Grande

Physics observables

arrival time and energy deposit by

charged particles in each detector ⇒ particle densities

muons from the KASCADE

detectors

≈10 m2 of plastic scintillator per

station

light detected and coverted into

electronic signal by PMTs

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 8

SLIDE 10

Trigger efficiency

KASCADE Piccolo-Stations Grande-Stations

x-coordinate฀[m] y-coordinate฀[m]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 Trigger-Cell฀17(18)

700
600
500
400
300
200
100

100

600 -500 -400 -300 -200 -100

100

fiducial area of ∼ 192,000 m2

(orange area),

trigger by 7/7 coincidence

/GeV) (E

10

log 6 6.2 6.4 6.6 6.8 7 7.2 7.4 7.6 trigger efficiency 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 proton - 7/7 iron - 7/7 all - 7/7 trigger all - 4/7 trigger

based on air shower simulation
full efficiency at E = 1016 eV, for

both proton and iron primaries

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 9

SLIDE 11

Shower reconstruction

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 10

SLIDE 12

Shower reconstruction

shower core: impact position of the shower axis at ground level = ⇒ Grande measurements arrival direction = ⇒ Grande measurements electron shower size Ne: total number of electrons arriving at

bservation level =

⇒ Grande measurements muon shower size Nµ: total number of muons arriving at

bservation level =

⇒ KASCADE measurements

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 10

SLIDE 13

Reconstruction procedure

X (Meters)

700
600
500
400
300
200
100

100 Y (Meters)

700
600
500
400
300
200
100

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

Time (ns) 4845 5554

(x,y)=(-115 m, -223 m), (θ, φ)=(11◦, 338◦)

Distance From Shower Axis [m] 100 200 300 400 500 )

2

*m ρ (

10

log

1

10 1 10

2

10

Charged (Grande) (KASCADE) µ + e) µ ( ) µ Lagutin (

log10(Ne) = 7, log10 Nµ = 5.7

Core position and total number of charged particle (Nch) by fitting the lateral distribution with a modified NKG function: ρch = Nch · C(s) · r r0 s−1.6 ·

1 + r

r0 s−3.4 r0 = 30m

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 11

SLIDE 14

Reconstruction procedure

X (Meters)

700
600
500
400
300
200
100

100 Y (Meters)

700
600
500
400
300
200
100

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

Time (ns) 4845 5554

(x,y)=(-115 m, -223 m), (θ, φ)=(11◦, 338◦)

Distance From Shower Axis [m] 100 200 300 400 500 )

2

*m ρ (

10

log

1

10 1 10

2

10

Charged (Grande) (KASCADE) µ + e) µ ( ) µ Lagutin (

log10(Ne) = 7, log10 Nµ = 5.7

Total number of muons (Nµ) by fitting the muon lateral distribution with a Lagutin function: ρµ = Nµ· 0.28 3202 · r 320 −0.69 ·

1 +

r 320 −2.39 ·

1 +
r

10 · 320 2−1

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 11

SLIDE 15

Reconstruction procedure

X (Meters)

700
600
500
400
300
200
100

100 Y (Meters)

700
600
500
400
300
200
100

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

Time (ns) 4845 5554

(x,y)=(-115 m, -223 m), (θ, φ)=(11◦, 338◦)

Distance From Shower Axis [m] 100 200 300 400 500 )

2

*m ρ (

10

log

1

10 1 10

2

10

Charged (Grande) (KASCADE) µ + e) µ ( ) µ Lagutin (

log10(Ne) = 7, log10 Nµ = 5.7

Total number of electrons (Ne) by subtracting the estimated muon content from the estimated charged particles content.

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 11

SLIDE 16

Reconstruction accuracies sim/data

)

true e

(N

10

log 5 5.5 6 6.5 7 7.5 8 8.5

true e

)/N

true e

N

rec e

(N

0.2

0.2 0.4 0.6

proton iron

)

true e

(N

10

log 5 5.5 6 6.5 7 7.5 8 8.5 Core accuracy [m] 5 10 15 20 25 30

proton iron

statistical uncertainty for Ne at full efficiency around 25 %
systematics change from less than 5% at threshold to 15%
small dependence on primary particle type
core accuracy ≈ 6 m

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 12

SLIDE 17

Reconstruction accuracies sim/data

(Size_KASCADE)

10

log 5.8 6 6.2 6.4 6.6 6.8 7 7.2 Size ∆

0.1
0.05

0.05 0.1 0.15 (Size_KASCADE)

10

log 5.8 6 6.2 6.4 6.6 6.8 7 7.2 Core accuracy 2 4 6 8 10 12

Trigger from Grande
Maximum density in the central station of the

cluster overlapping with KASCADE

KASCADE reconstruction used as reference

KASCADE Piccolo-Stations Grande-Stations x-coordinate฀[m] y-coordinate฀[m]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 Trigger-Cell฀17(18)

700
600
500
400
300
200
100

100

600 -500 -400 -300 -200 -100

100

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 12

SLIDE 18

Reconstruction accuracies sim/data

)

true µ

(N

10

log 4.5 5 5.5 6 6.5 7

true µ

)/N

true µ

N

rec µ

(N

0.2

0.2 0.4 0.6

proton iron

)

true e

(N

10

log 5 5.5 6 6.5 7 7.5 8 8.5 Angular accuracy [deg] 0.5 1 1.5 2

proton iron

statistical uncertainty for Nµ at full efficiency around 20 %
bias of 10% to -5% in energy (muon) dependence
Angular accuracy < 0.5◦ up to 40◦

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 13

SLIDE 19

Spectra

SIZE (electron) SPECTRA

)

e

(N

10

Log

6 6.5 7 7.5 8

]

1

sr

1

s

2

[m

e

dI/dN

21

10

20

10

19

10

18

10

17

10

16

10

15

10

14

10

13

10

12

10 ° 0-17 ° 17-24 ° 24-30 ° 30-35 ° 35-40

987 days of data taking
fiducial area of ≈ 0.2 km2
≈ 880, 000 events

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 14

SLIDE 20

Ne − Nµ correlation

µ

lg N

4.5 5 5.5 6 6.5 7

e

lg N

5 5.5 6 6.5 7 7.5 8 8.5

number of showers

1 10

2

10

3

10

4

10 Proton

Carbon

Iron

10 PeV 30 PeV 100 PeV 300 PeV 1 EeV

(Ne, Nµ) = f (E, m)

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 15

SLIDE 21

Energy spectrum

correlation Nch with E0 from simulation → good

reconstruction accuracy, BUT very much composition dependent

correlation Nµ with E0 from simulation → problems with

reconstruction accuracy, less composition dependent

estimation of the primary energy as E0(Nch, Nµ) → no

composition dependence! THEY ALL REQUIRE ASSOMPTION ON HIGH ENERGY HADRONIC INTERACTION MODELS

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 16

SLIDE 22

Energy estimation

log10 (Nch/Nµ)p,Fe = cp,Fe · log10(Nch) + dp,Fe

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 5.5 6 6.5 7 7.5 8 8.5

log10(Nch) log10(Nch/Nμ)

r = log10(Nch/Nµ) − log10 (Nch/Nµ)p log10 (Nch/Nµ)Fe − log10 (Nch/Nµ)p

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 17

SLIDE 23

Energy estimation

6 6.5 7 7.5 8 8.5 9 5.5 6 6.5 7 7.5 8 8.5

log10(Nch) log10(E/GeV)

log10(Eest) = (ap + ∆a · r) · log10(Nch(θ)) + (bp + ∆b · r)

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 17

SLIDE 24

Energy estimation

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 18

SLIDE 25

Mass composition analysis method

statistical methods to infer cosmic rays mass
search of mass-sensitive observables
classification of an air shower through kNN method

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 19

SLIDE 26

Parameters relevance

)

rec e

(N

10

log 5.5 6 6.5 7 7.5 8 8.5 9 )

rec µ

(N

10

median log 4 4.5 5 5.5 6 6.5 7 7.5 8

proton iron data

error bars represent the spread of the distribution in each bin

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 20

SLIDE 27

KNN

classification method: comparison of each data point with the “K nearest neighbours” in reference samples

data point, proton, iron
characterization of each point

through Nch and Nµ

Mahalanobis distance:
(x1 − x2)T(S)−1(x1 − x2)

with S covariance matrix

S for each reference sample separately
K number to be chosen on analysis base
assignment through majority vote

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 21

SLIDE 28

Training

misclassification rates Pωp→ωFe
misclassification matrix

Pωp→ωp PωFe→ωp Pωp→ωFe PωFe→ωFe n∗

p

n∗

Fe

=

np nFe

separability index G = Pωp→ωp · PωFe→ωFe
5 zenith angle bins: 0◦ − 40◦
different energy ranges: 1016 eV to 1018 eV

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 22

SLIDE 29

Training results

proton relative error 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 ° < 17.6 θ ≤ ° ° < 24.99 θ ≤ ° 17.6 ° < 30.73 θ ≤ ° 24.99 ° < 35.63 θ ≤ ° 30.73 ° < 40 θ ≤ ° 35.63 )

est

(E

10

log 7.2 7.4 7.6 7.8 8 8.2 8.4 8.6 8.8 iron relative error 0.05 0.1 0.15 0.2 0.25

misclassification better

than 25%

separability better than

80%

best k=9

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 23

SLIDE 30

kNN on KASCADE-Grande data

)

rec µ

(N

10

log 4 4.5 5 5.5 6 6.5 7 )

rec e

(N

10

log 5 5.5 6 6.5 7 7.5 8 8.5 9

proton iron data

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 24

SLIDE 31

kNN on KASCADE-Grande data

/GeV)

est

(E

10

log

7 7.5 8 8.5 9

relative mean number

0.2 0.3 0.4 0.5 0.6 0.7 0.8 proton iron

change to heavier composition up to E = 3 · 1016 eV

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 24

SLIDE 32

kNN on KASCADE-Grande data

/GeV)

est

(E

10

log

7 7.5 8 8.5 9

relative mean number

0.2 0.3 0.4 0.5 0.6 0.7 0.8 proton iron

between 3 · 1016 eV to 1018 eV: ≈ 70% iron-like
E > 1018 eV: 6 events per zenith bin, large fluctuation,

compatible with constant composition at 1.5 σ level.

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 24

SLIDE 33

kNN: systematic sources

method dependent on hadronic interaction model used
contribution of other primaries to the measured frequencies of

proton-like and iron-like air showers:

He → 80% proton, 20% iron
C → 50% proton, 50% iron
Si → 20% proton, 80% iron
systematic underestimation of energy ≈ −5%

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 25

SLIDE 34

Summary

Shower reconstruction is accurate enough for analysis
Methods to reconstruct the energy spectrum available
Increase of iron fraction up to E = 3 · 1016 eV → consistent

with a decrease of the light primaries

at E > 3 · 1016 eV no evident change of composition observed:

≈ 70% iron-like air showers

no transition to extragalactic (light) component for

E < 1018 eV

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 26

SLIDE 35

kNN on other primaries

/GeV)

est

(E

10

log

7 7.5 8 8.5 9

relative mean number

0.2

0.2 0.4 0.6 0.8 1 1.2 proton iron

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 27

SLIDE 36

kNN on other primaries

/GeV)

est

(E

10

log

7 7.5 8 8.5 9

relative mean number

0.2 0.3 0.4 0.5 0.6 0.7 0.8 proton iron

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 27

SLIDE 37

kNN on other primaries

/GeV)

est

(E

10

log

7 7.5 8 8.5 9

relative mean number

0.2 0.4 0.6 0.8 1 proton iron

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 27

SLIDE 38

Shower profiles

]

2

atmospheric depth [g/cm

100 200 300 400 500 600 700 800 900 1000

number of electrons

4

10

5

10

6

10

7

10

8

10 hydrogen iron 10PeV 100PeV

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 28

SLIDE 39

Shower profiles

]

2

atmospheric depth [g/cm

100 200 300 400 500 600 700 800 900 1000

number of muons

3

10

4

10

5

10

6

10 hydrogen iron 10PeV 100PeV

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 28

SLIDE 40

Shower profiles

core distance [m]

200 400 600 800 1000

]

2

particle densities [m

3

10

2

10

1

10 1 10

2

10

3

10

4

10 hydrogen iron 10PeV 100PeV

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 28

SLIDE 41

Shower profiles

core distance [m]

200 400 600 800 1000

]

2

particle densities [m

3

10

2

10

1

10 1 10 hydrogen iron 10PeV 100PeV

Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 28