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High-energy Electron Spectrum From PPB-BETS Experiment In Antarctica

High-energy Electron Spectrum From PPB-BETS Experiment In Antarctica. Kenji Yoshida 1 , Shoji Torii 2 on behalf of the PPB-BETS collaboration 1 Shibaura Institute of Technology, Japan 2 Waseda University, Japan. PPB-BETS Observations in Antarctica. PPB-BETS : Imaging calorimeter

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High-energy Electron Spectrum From PPB-BETS Experiment In Antarctica

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  1. High-energy Electron Spectrum From PPB-BETS Experiment In Antarctica Kenji Yoshida1, Shoji Torii2 on behalf of the PPB-BETS collaboration 1Shibaura Institute of Technology, Japan 2Waseda University, Japan

  2. PPB-BETS Observations in Antarctica • PPB-BETS : Imaging calorimeter • Event selection • Energy measurements • Direction measurements • Observation: • 13 days in Jan. 2004 • Altitude: ~35km 9 r.l. Side view of the detector Trajectory of PPB-BETS HEAD 2010

  3. R.E. distributions Observed Events 100GeV Electrons 250GeV Protons Electron Candidate Proton Candidate Electron Selection- Proton Rejection - • Proton rejection by using the lateral spread of the cascade shower • R.E. parameter = Ratio of energy deposition within 5mm from the shower axis to the total HEAD 2010

  4. Electron Candidate e gamma Gamma-ray Candidate Electron Selection- Gamma-ray Rejection - • Fiber signals along the shower axis at top layer => Separation between electrons and gamma rays Distributions of the nearest hit fiber positions from the shower axis HEAD 2010

  5. Determination of Electron Energy The number of shower particles at shower maximum => Electron energy HEAD 2010

  6. Electron Energy Spectrum- BETS+PPB-BETS - cn2= 1.605 (d.o.f.=11) A power-law spectrum : Acceptable at the 95% C.L. HEAD 2010

  7. Search for Anisotropies of Cosmic-ray Electrons above 100GeV Ratio of the observed arrival distribution (>100GeV) to isotropic distribution along the Galactic longitude => No significant anisotropies within statistical errors HEAD 2010

  8. Summary • BETS + PPB-BETS cosmic-ray electron spectrum from 10GeV to 800GeV: => A power-law spectrum E-3.05 • Search for cosmic-ray electron anisotropies above 100GeV by PPB-BETS: => Isotropic distribution within statistical errors • For detection of nearby source signatures => Electron observation up to 10 TeV by CALET HEAD 2010

  9. Backup HEAD 2010

  10. Effective Geometrical Factor (SW) Simulation under the same condition of the observations and analysis 30th ICRC (Merida)

  11. Derivation of Cosmic-Ray Electron Energy Spectrum • Ne: The Number of electron candidates • CRE: Correction factor of proton contamination in the R.E. cut with energy dependence (~0.68) • Ceg: Correction factor of gamma-ray contamination (~0.84) • Cenh: Correction of enhancement of flux due to the energy resolution (0.97) • C2nd: Correction of secondary electrons in the atmosphere (1.3x10-5 (m-2s-1sr-1GeV-1) @100GeV) • Catm: Correction of energy loss of primary electrons in the overlying atmosphere (1.37) 30th ICRC (Merida)

  12. Uncertainty of Determination of Arrival Directions Differences between Geomagnetic Aspect Sensor and Sun Aspect Sensor: ~5 deg Angular resolution with scintillating fibers of PPB-BETS detector: ~0.5 deg 30th ICRC (Merida)

  13. Atmospheric Gamma-ray Spectrum => Consistent with ECC HEAD 2010

  14. Proton Rejection Power Reduction of proton background: On-board Trigger by the 1st and 2nd levels: ~ 95 % Selection of Contained Events in Detector: ~ 90 % Lateral spread of cascade shower: ~95 % Total Rejection Power of Protons: ~20 x 10 x 20 = 4x 103 HEAD 2010

  15. Basic Parameters of PPB-BETS 30th ICRC (Merida)

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