Knee 領域での空気シャワー実験

研究会「超高エネルギー宇宙線とハドロン構造」 @KEK, 2008 年 4 月 25 日　

瀧田　正人東京大学宇宙線研究所

M.Nagano, A.A.Watson (2000)

Cosmic Ray Energy Spectrum

Cosmic Ray Energy Spectrum

Sommers (ICRC2001)

Experiment site g/cm2 e μ h C

AKENO Japan (35.5N, 138.5E) 930 〇 1 GeV

BLANCA Utah(40.2N,112.8W) 870 〇 〇

CASA-MIA Utah (40.2N,112.8W) 870 〇 800 MeV

DICE 860 〇 800 MeV 〇

EAS-Top Italy (42.5N,13.6E) 820 〇 1 GeV

HEGRA La Palma (28.8N,17.9W)

790 〇 〇

KASCADE (electrons/muons) Germany (49.N, 8.E) 1022 〇 230 MeV

KASCADE (hadrons/muons) 1022 230 MeV 50 GeV

KASCADE (neural network) 1022 〇 230 MeV

MSU 1020 〇

Mt. Norikura Japan 735 〇

Tibet Tibet (30.1N,90.5E) 606 〇

Tunka-13 680 〇

Yakutsk (low energy) 1020 〇

All particle spectrum

Knee around 3-5 PeV

ICRC2003 M. Takita

All particle energy spectrum

ICRC2007 Y. Tsunesada (BASJE)

Energy dependence of< ln A>

Research purpose

Thus, measurements of the primary cosmic rays around the "knee" are very important and its composition is a fundamental input for understanding the particle acceleration mechanism that pushes cosmic rays to very high energies.

According to the Fermi

acceleration with supernova

blast waves, the acceleration

limit Emax≒Z * 100 TeV.

The position of "knee"

must be dependent on

electric charge Z

KASCADEKASCADE

e/ Hadron

Energy Spectrum of Single Elements

Kascade data 2005:different results with different Monte Carlo

approaches in data reconstruction. Rigidity scenario not confirmed.

Kascade data Kascade data 2003:seem to confirm the rigidity

model.

BUT

KASCADE : Astroparticle phys. 24 (2005) 1-25

KASCADE : Astroparticle phys. 24 (2005) 1-25

TIBETTIBETYangbajing , Tibet, China 90 ゜ 53E, 30 ゜ 11N, 4,300 m a.s.l. (606g/cm2)

BD&EC

Air Shower array

Phys. Lett. B. 632(2006)58

Tibet-II Air Shower array

Tibet-I to Tibet-II/HD

Number of detector I : 45 II : 185 HD: 109

Mode Energy I : 10 TeV II : 10 TeV HD: 3 TeVArea I : 7 ,650 m2

II : 37,000 m2

HD: 5,200 m2

Characteristics of the Tibet Hybrid Experiment • High altitude (4300m a.s.l. 606 g/cm2). Energy determination is made under minimum chemical-

composition dependence around the knee.

• Observe core structure by burst detectors (BD)

& emulsion chambers (EC)

Select air showers of light-component origin by high

energy core detection. (σ A∝ 2/3)

Young showers are mostly of proton and helium origins.

Air shower axis is known with Δr < 1m.

Ne and s are determined precisely.

• Smaller interaction-model dependence

for forward region than backward.

検出方法検出方法

宇宙線宇宙線

空気シャワー空気シャワーシンチレーション光シンチレーション光

2nd particle density 2nd particle timing

Cosmic ray energy Cosmic ray direction

Air Shower Detection

到着

時間

(ns)

粒子

数

~10 TeV

シャワーサイズ Ne の計算（ NKG 関数）

~3 ｘ 1016eV

Constant fitting-0.0034o 0.011o+

Systematic pointing error < 0.01o

Absolute EnergyScale error –4.4% +- 7.9%stat +- 8%sys

Energy dependence ofDisplacementsCaused by Geomagnetic field

Verification Absolute energy scale Pointing error

Cosmic Ray Energy Calib. by the Moon’ Shadow by Tibet-III

EC and BD Total EC area : 80 m2

EC and BD

1) A structure of each EC used here is a multilayered sandwich of lead plate and photosensitive x-ray films, photosensitive layers are put every 2 (r.l.) (1 r.l.=0.5cm) of lead in EC.

Total thickness of lead plates is 14 r.l.2) family is mostly cascade products ind

uced by high energy 0 decay - rays which are generated in the nuclear interactions at various depths.

3) It is worthwhile to note that the major behavior of hadronic interactions as well as the primary composition are fairly well reflected on the structure of the family observed with EC.

-M.C.Simulation-Hadronic int.model

• CORSIKA ( Ver. 6.030 )

　　 – QGSJET01–

　　 – SIBYLL2.1 –

Primary composition model•HD (Heavy Dominant)•PD (Proton Dominant)

HD model

1014eV 1015eV 1016eV

Proton 22.6 11.0 8.1

He 19.2 11.4 8.4

Iron 22.2 39.1 51.7

Other 35.6 38.2 31.7

PD model

1014eV 1015eV 1016eV

Proton 39.0 38.1 37.5

He 20.4 19.4 19.1

Iron 9.4 9.9 10.2

Other 30.4 31.7 33.0

The experimental conditions for detecting family (E >= 4TeV, N=4, E >=20 TeV) events with EC are adequately taken into account. For example, our EC has a roof, namely, the roof simulation and EC simulation are also treated.

HD model PD model

Primary composition model

Model Dependence of -family (Generation+Selection) Efficiency in EC

QGSJET

SIBYLL

SIBYLL/QGSJET~1.3SIBYLL/QGSJET

～ 1.3

SIBYLL

QGSJET

SIBYLL

QGSJET

Model Dependence of Air Shower Size Accompanied by -family

Procedures to ObtainPrimary Proton Spectrum

( -family selection criteria : Emin=4TeV, Ng=4, sumE >=20TeV, Ne >=2x105 )

AS+ECfamily matching event ANN Proton identification(Correlations)(E,N,< R >,<ER>,sec(θ), Ne )

Int. models QGSJET Expt.(80m2)

(1996-1999)

(699days)

SIBYLL Expt.(80m2)

(1996-1999)

(699days)

Primary HD PD HD PD

Total sampling primary

2x108 1x108 2x108 1x108

Number of -family

5252 7303 177 6801 9655 177

Selected by ANN

(T <=0.4)

3308 4636 111 4312 6192 112

Event Matching between EC+BD+AS

AS+ECfamily matching event ANN Proton identification(Correlations)(E,N,< R >,<ER>,sec(θ), Ne )

Measurement Parameter

Location(x, y)

Time (t)

EC(family) AS BD

E,N,< R >,<ER>,sec(θ)

Direction(θ, )Y 　　　 　　　　　 NO 　　　　　　 Y

　 Y Y 　 NONO 　　　 Y 　 Y

Ne E0 Nb

AS&family matching bytime coincidence, Nburst>105 and test

cm)10(center burst andfamily between Distance:,

deg.) 0.2( AS andfamily between angle Opening:

)()()(

x

2222

y

yx

yx

yx

2

177 ev selected

192 + 14 ev expected

Fractions of P, He, M, Fe components (MC) making air showers accompanied by γ-families

Model Energy(eV) P He M Fe

QGSJET+HD 1014-1015 87.3±1.2 12.7±1.2 0 0

(%) 1015-1016 58.9±0.9 27.2±0.8 12.3±0.9 1.6±0.3

SIBYLL+HD 1014-1015 87.2±0.8 12.8±0.8 0 0

(%) 1015-1016 57.3±0.7 24.2±0.7 16.9±0.8 1.6±0.3

QGSJET+PD 1014-1015 91.8±0.8 8.2±0.8 0 0

(%) 1015-1016 80.0±0.6 16.0±0.6 3.4±0.4 0.6±0.1

SIBYLL+PD 1014-1015 94.2±0.6 5.8±0.6 0 0

(%) 1015-1016 78.7±0.6 17.9±0.6 3.4±0.4 0.06±0.01

Selection of proton-induced events by Artificial Neural Network (ANN) 　　（１） sumE 　（ Total energy EC ）　（２）　 Ng 　 （ number of ganma family EC ）　（３） < R > ( mean lateral spread ：　　　　　　　　 ( 　 < R > ～　 (<PT>×H) / <E>

EC)

　（４） <ER> （ mean energy flow spread EC ）　（５） sec(θ) ( Zenith angle of gamma family EC ）　（６） Ne （ Shower size of the tagged air shower

s AS ）

Selection of proton-induced events

with ANN

Parameters for training( sumE, Ng, < R >, <ER>, sec(θ), Ne )

Target value for protons=0

others=1

Define threshold value “Tth”

Selection efficiency of proton

events as a function of “Tth”

Efficiency~75%

Tth=0.4

Purity~85%

Target Value (T)

Comparison of Target Value Distribution. between DATA and MC

Back check: Selection of proton-induced events by ANN

Air shower size spectrum of p-like events vs MC (for proton like events (ANN out-put <=0.4))

Primary energy estimation ( for proton like events )( 1.0 < sec(theta)

<=1.1 )

Back check: Conversion factor for p-like EV ( by QGSJET + HD 　（ ANN out-put <= 0.4

) )

Energy resolution 　

Primary proton spectrum

Preliminary

(KASCADE data: astro-ph/0312295)

All

ProtonKASCADE (P)

Present Results

(a) ( by QGSJET model) (b) ( by SIBYLL model )

Primary helium spectrum

(a) (by QGSJET model) (b) (by SIBYLL model)

Primary ratio

Tibet

KASCADE

(a) (by QGSJET model) (b) ( by SIBYLL model ）

All –(P+He)All

733 Scintillators

Tibet III　 AS array + Burst Detector

Burst hut

80 m2 coverage by 100 burst detectors.

Pb 7r.l. Iron 1cm

Scint. 2cm

Box

Phase II hybrid experiment

Scintillator 50cm x 160cm x 2cm.viewed with 4 PhotoDiodes.Measure size and position of the burst (e.g., e.m. cascade)

Electromagnetic component over GeV is responsible for burst size.Scint. was calibrated by accelerator beam.

Proton+Helium spectrum

Phase IPhase IPhase II

Proton+Helium spectrum

Phase IPhase II

Tibet AS(~8.3 万 m2)

+MD(384ch, ~104m2)

Tibet AS + MD の点源に対する感度

Tibet AS:Energy and direction of air shower

Cosmic ray(P,He,Fe…)

Particle density & spreadSeparation of particles

Tibet AS+YAC(1~5 千m2)

青が期待値

YAC

Knee p, He, Fe100TeV

Summary

( 1 ) All particle E spectrum -> KASCADE ~= Tibet

( 2 ) Composition

KASCADE: small stat, but large syst(2~5) x100%

Rigidity scenario not confirmed

　　　　　　　　　　 All particle knee bend by light elements

Tibet: Large stat(~10%), but small syst (~30% for p)

The knee of all particle spectrum is

composed of nuclei heavier than P + He