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The science objectives for CALET
Kenji Yoshida (Shibaura Institute of Technology)
for the CALET Collaboration
Introduction
August 16, 2011 32nd ICRC (Beijing) 2
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
August 16, 2011 32nd ICRC (Beijing) 3
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
August 16, 2011 32nd ICRC (Beijing) 4
Expected electron intensity distribution Expected anisotropy with energy
=> Identifiable anisotropy toward nearby SNRs such as the Vela
Vela
D ~ 10%
Gamma ray observations
August 16, 2011 32nd ICRC (Beijing) 5
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
August 16, 2011 32nd ICRC (Beijing) 6
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
August 16, 2011 32nd ICRC (Beijing) 7
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
August 16, 2011 32nd ICRC (Beijing) 8
=> 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
August 16, 2011 32nd ICRC (Beijing) 9
=> 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