The science objectives for CALET

Kenji Yoshida (Shibaura Institute of Technology)

for the CALET Collaboration

Introduction

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Major goals in cosmic-ray study: • To make clear the cosmic-ray origin, acceleration and

propagation mechanisms

One of the most important unresolved problems in astrophysics: • Nature and origin of dark matter• What the dark matter is made of

=> CALET for all-sky electron, gamma ray, and nuclear components observations on the JEM-EF of the ISS to study these scientific objectives

Other scientific objectives:• B.Rauch, Capability of the CALET experiment for measuring elemental abundances of

galactic cosmic ray nuclei heavier than nickel (Z=28), ID690, OG1.5• K.Yamaoka, The CALET Gamma-ray Burst Monitor (CGBM), ID839, OG2.5

Identification of electron sources

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Some nearby sources, e.g. Vela SNR, might leave unique signatures in the electron energy spectrum in the TeV region (Kobayashi et al. 2004)

=> Identification of the unique signature from nearby SNRs such as Vela in the electron spectrum by CALET

Simulated electron energy spectrum of the CALET for 5yr observations from a SNR scenario model (Kobayashi et al. 2004)

Anisotropy of electrons

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Expected electron intensity distribution Expected anisotropy with energy

=> Identifiable anisotropy toward nearby SNRs such as the Vela

Vela

D ~ 10%

Gamma ray observations

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Vela pulsar

Geminga pulsar

Simulated CALET gamma-ray all sky map for 3yr (>10GeV)

=> Gamma-ray all sky survey for 10GeV-10TeV region by CALET

Extra-galactic diffuse gamma-ray spectra

CALET

Detection limit of Galactic diffuse gamma rays

Electron origin

proton origin

Indirect dark matter searchby electrons

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2yr (BF=40)or 5yr (BF=16)

Simulated e++e- spectrum for 2yr from Kaluza-Klein dark matter annihilations with m=620GeV and BF=40

Simulated e++e- spectrum for 2yr from decaying dark matter for a decay channel of D.M.-> l+l-n with m=2.5TeV and t = 2.1x1026s

=> CALET has a potential to detect electron + positron signals from dark matter annihilation/decay

(A.Ibarra et al. 2010)

Indirect dark matter search by gamma rays

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Simulated gamma-ray line spectrum for 2yr from neutralino annihilation toward the Galactic center with m=820GeV, a Moore halo profile, and BF=5

Simulated extra-galactic gamma-ray spectrum for 2yr from decaying dark matter for a decay channel of D.M.-> l+l-

n with m=2.5TeV and t = 2.1x1026s

=> CALET has a potential to detect gamma-ray signals from dark matter annihilation/decay with the excellent energy resolution of 2%

(A.Ibarra et al. 2010)

EGRET

Nuclear components observations

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=> Confirmation of the spectral hardening and the spectral changing around the knee

Expected P and He spectra with a power-law index of -2.70

Expected B/C with a diffusion coefficient of D0E^d (d=0.45)

=> Severe restriction on the propagation models

Summary• Unique signatures of the electron spectrum in TeV region• Anisotropy of electrons toward the nearby sources

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=> Identification of nearby cosmic-ray electron sources by the CALET electron observations in 10GeV – 20TeV

• Gamma-ray point sources, Galactic and extra-galactic gamma-ray diffuse emission=> All-sky survey by high-energy gamma rays in 10GeV – 10TeV with CALET

• What is the dark matter made of=> Indirect dark matter search by the CALET hybrid observations of electrons and gamma rays

• Cosmic-ray propagation mechanisms=> Severe restrictions by CAELT nuclear components observations in several 10GeV – 1000TeV