1. 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

2. March 3, 20102HEAD 2010 Side view of the detector 9 r.l. Trajectory of PPB-BETS PPB-BETS Observations in Antarctica Observation: 13 days in Jan. 2004 13 days in Jan. 2004 Altitude: ~35km Altitude: ~35km PPB-BETS : Imaging calorimeter Event selection Event selection Energy measurements Energy measurements Direction measurements Direction measurements

3. 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 March 3, 2010HEAD 20103 Observed Events 100GeV Electrons 250GeV Protons R.E. distributions Electron Candidate Proton Candidate

4. Electron Selection - Gamma-ray Rejection - Fiber signals along the shower axis at top layer => Separation between electrons and gamma rays March 3, 2010HEAD 20104 Electron Candidate Gamma-ray Candidate e gamma Distributions of the nearest hit fiber positions from the shower axis

5. Determination of Electron Energy March 3, 2010HEAD 20105 The number of shower particles at shower maximum => Electron energy The number of shower particles at shower maximum => Electron energy

6. Electron Energy Spectrum - BETS+PPB-BETS - March 3, 2010HEAD 20106 A power-law spectrum : Acceptable at the 95% C.L.  2 = 1.605 (d.o.f.=11)

7. Search for Anisotropies of Cosmic-ray Electrons above 100GeV March 3, 2010HEAD 20107 => No significant anisotropies within statistical errors Ratio of the observed arrival distribution (>100GeV) to isotropic distribution along the Galactic longitude

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 March 3, 2010HEAD 20108

9. Backup March 3, 2010HEAD 20109

10. 4 July 200730th ICRC (Merida)10 Effective Geometrical Factor (S  ) Simulation under the same condition of the observations and analysis

11. 4 July 200730th ICRC (Merida)11 Derivation of Cosmic-Ray Electron Energy Spectrum ◆ N e : The Number of electron candidates ◆ C RE : Correction factor of proton contamination in the R.E. cut with energy dependence (~0.68) ◆ C eg : Correction factor of gamma-ray contamination (~0.84) ◆ C enh : Correction of enhancement of flux due to the energy resolution (0.97) ◆ C 2nd : Correction of secondary electrons in the atmosphere (1.3x10 -5 (m -2 s -1 sr -1 GeV -1 ) @100GeV) ◆ C atm : Correction of energy loss of primary electrons in the overlying atmosphere (1.37)

12. 4 July 200730th ICRC (Merida)12 Uncertainty of Determination of Arrival Directions Angular resolution with scintillating fibers of PPB-BETS detector: ~0.5 deg Differences between Geomagnetic Aspect Sensor and Sun Aspect Sensor: ~5 deg

13. Atmospheric Gamma-ray Spectrum March 3, 2010HEAD 201013 => Consistent with ECC

14. Proton Rejection Power March 3, 2010HEAD 201014 Reduction of proton background: Total Rejection Power of Protons: ~20 x 10 x 20 = 4x 10 3 On-board Trigger by the 1st and 2nd levels: ~ 95 % Selection of Contained Events in Detector: ~ 90 % Lateral spread of cascade shower: ~95 %

15. 4 July 200730th ICRC (Merida)15 Basic Parameters of PPB-BETS Instrument Weight~200 kg Total Weight (including ballast)~480 kg Power Consumption70 W Data Transfer Rate (Iridium Phone)2.4 kbps (Down Link to the Station)64 kbps Energy Range10~1000 GeV Geometrical Factor (SW)500 ~ 600 cm 2 sr Energy Resolution10~25 % Angular Resolution0.35 ~ 0.60 deg.