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The BESS Program

Akira Yamamoto (KEK) for the BESS collaboration SpacePart-06, Beijing, April 20, 2006. The BESS Program. Outline. BESS Experiment and Spectrometer Recent and New Results BESS TeV : Precise measurement of cosmic-rays BESS-Polar I : Search for antiparticle of primary origin

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The BESS Program

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  1. Akira Yamamoto (KEK) for the BESS collaboration SpacePart-06, Beijing, April 20, 2006 The BESS Program

  2. Outline • BESS Experiment and Spectrometer • Recent and New Results • BESS TeV : Precise measurement of cosmic-rays • BESS-Polar I : Search for antiparticle of primary origin • Plan for future • Summary

  3. High Energy Accelerator Research Organization(KEK) The University of Tokyo Kobe University Institute of Space and Astronautical Science/JAXA BESS Collaboration As of April, 2006 National Aeronautical and Space Administration Goddard Space Flight Center BESS Collaboration University of Maryland University of Denver (Since June 2005)

  4. Balloon-borne Experiment with a Superconducting Spectrometer Search for Primordial Antiparticle antiproton: Novel primary origins (PBH,DM) antihelium: Asymmetry of matter/antimatter Precise Measurement of Cosmic-ray flux: highly precise measurement at < 1 TeV BESS

  5. Rigidity measurement SC Solenoid (L=1m, B=1T) Min. material (4.7g/cm2) Uniform field Large acceptance Central tracker (Drift chamber d ~200mm Z, m measurement R,b --> m = ZeR 1/b2-1 dE/dx --> Z BESS Detector • JET/IDC • Rigidity TOF b, dE/dx √

  6. MDR 1.4 TV BESS-98 MDR 200 GV BESS-TeV Deflection Resolution

  7. BESS-TeV Spectrometer TOF ODC MAGNET • JET/IDC

  8. Progress of BESS Experiment 1993~ 2000, BESS, North Canada 2002, BESS-TeV 1999, 2001, BESS-Ground, Japan 2001, BESS-TeV, Fort Sumner 2004, BESS-Polar I, Antarctica 10 scientific balloon flightsduring1993-2004

  9. Primary Cosmic-ray Spectra (1998: Bess-98, AMS-I, Caprice) Error: < +/-5 % @ 100 GeV Sanuki et al. ApJ. 545 (2000) 1135

  10. Primary Cosmic-ray Spectra (BESS-TeV) Error: < +/-15 % @ 500 GeV Haino et al. PLB 594 (2004) 35

  11. F = f Ek-g Proton (Ek> 30 GeV) f = (1.37 ± 0.12)x104 g= 2.732 ± 0.022 Helium (Ek> 20 GeV) f = (7.06 ± 1.15)x102 g= 2.699 ± 0.059 Fitting based on the BESS-TeV results only BESS-TeV Result Anchor the P and He Spectra in Low Energy (< TeV)

  12. Rigidity Measurement Precise spectra proton (0.2~500 GeV) helium (0.2~250 GeV/n) antiproton (0.2~ 4 GeV) Anchor the spectrum in the lowest energy region. 104 • BESS Flux (m2 sr s GeV)-1 10-28 0.1 1012 Energy (GeV) Low Energy Cosmic-ray SpectraPrecisely Measured by BESS

  13. Search for Antiprotons of Cosmic Origins Primary Detectable Secondary SUSY PBH • Most antiprotons are secondary products from nuclear interactions of primary cosmic rays with the ISM. • “Exotic” sources may relatively enhance antiproton flux at energies well below or above secondary peak.

  14. Observation of Cosmic-rayAntiprotonsin p-bar/p Ratio 1979:First observation (Golden et al) 1979: Russian PM (Bogomolov et al) 1981: Excess reported (Buffington et al) 1985: ASTROMAG Study Started 1987:LEAP, PBAR (upper limits) 1991: MASS 1992:IMAX (16 antiprotons) 1993:BESS (6 antiprotons), TS93 1994:CAPRICE94, HEAT-e 1996: Solar minimum 1998: CAPRICE98, AMS-01 2000: HEAT-pbar 2004:BESS-Polar 2006:PAMELA 2007: Solar minimum, BESS-Polar 2008:AMS-02 Before the BESS Experiment

  15. p/p Ratio Observation of Cosmic-rayAntiprotonsin p-bar/p Ratio 1979:First observation (Golden et al) 1979: Russian PM (Bogomolov et al) 1981: Excess reported (Buffington et al) 1985: ASTROMAG Study Started 1987:LEAP, PBAR (upper limits) 1991: MASS 1992:IMAX (16 antiprotons) 1993:BESS (6 antiprotons), TS93 1994:CAPRICE94, HEAT-e 1996: Solar minimum 1998: CAPRICE98, AMS-01 2000: HEAT-pbar 2004:BESS-Polar 2006:PAMELA 2007: Solar minimum, BESS-Polar 2008:AMS-02 BESS By the BESS Experiment

  16. Mostly secondary particles with specific peak at 2 GeV Study: Propagation model Solar modulation Search for: Novel Primary Origin? (PBH, DM) Flatter spectrum in low energy 10-1 BESS(95+97) BESS(93) IMAX CAPRICE Pbar flux [m-2sr-1sec-1GeV-1] 10-2 10-3 10-1 1 10 Kinetic Energy (GeV) Low Energy Cosmic-ray Antiprotonsin last solar minimum (1995~97) More Statistics necessary ->> Long-duration Flight

  17. Very precise measurement Low energy Antiprotons Around south-pole, Antarctica Long duration flight High latitude Solar minimum With a new spectrometer Ultimately small material Ultra-thin superconducting solenoid BESS-Polar Experiment

  18. BESS-2000 BESS-Polar TOF Upper Coil JET/IDC MTOF 5g/cm2 ACC 18g/cm2 10g/cm2 TOF Lower Feature of BESS-Polar Spectrometer Minimize material in spectrometer New detector (Middle TOF) Energy range extended down to 0.1 GeV Low power electronics Solar Power System, Longer life of cryogen, LHe Long duration flight

  19. 8.5 dayflight successful 35-37 km in altitude 900 million events recorded - Acceptance limited to ~ 0.2 m2.sr Altitude～38000m Residual air～4g/cm2 Floating BESS-Polar 2004

  20. Low Energy Antiproton Observedin BESS Polar I (in 2004) Preliminary ～2000 Antiproton Candidates • ~ 2000 antiproton (total) candidate observed • ~ 400 antiprotons below 1 GeV

  21. Lowest Energy Events Observed Antiproton event RGT -0.4GV 1/β 2.47 Limit by MTOF Trigger Limit by BTOF Trigger ★Kinetic Energy ～0.11GeV (@ TOA) ★Multi-track events to be further studied

  22. ＰＭＴ－ＨＶ Both-end Single-end Dead Antiprotons Observed(Preliminary) • 4~5 times statistics • (than that of 1997), • With ~0.2 m2sr (2/3), • 8 days flight 18/44 TOF-PMT turned-off

  23. Pbar/P Ratio Observation Extended • The measurement consistent with the prediction, Bieber et al.

  24. Progress in Antihelium Search • Preliminary Results • The upper limit of antihelium/helium ratio pushed down • ~5 x 10E-7 @ BESS-Polar I • Generally, two order of magnitude lowered by BESS in last ten years.

  25. Solar minimum in 2006~07 Realize further long duration flight of 20 days with two circle around the pole, 4~5 x BESS-Polar I statistics Further Plan for BESS-Polar II Record at Tiger flight

  26. Improvement toward BESS-Polar II

  27. BESS Polar II Observation(Expected) Antiproton Spectrum Search for Antideuteron and AntiHelium (Search for PBH)

  28. BESS-Polar Feature (3 years) (10+20 days) AMS02 PAMELA (3 years) BESS-Polar realize the best sensitivity in lowest energy Acceptance (m2sr) Flight Time Latitude Altitude (km) Launch AMS 0.5 3 years < 51.7 280~500 2008 PAMELA 0.0021 3 years <70.4 350-600 2006 BESS-Polar2 0.3 20 days > 75 36 2007

  29. Summary • BESS measured: • Precise Cosmic-rayProton (Helium)spectrum with errors within • 5 % @ 100 GeV, and 15 % @ 500 GeV • with anchoring the spectrum at the lowest energy • Low energy Antiprotonspectra at 0.1 - 4 GeV to • Mostly secondaries, • Useful information on cosmic-ray propagation and solar modulation • Search for novel primary origin suchs as PBH, • Antidueteron search with the first upper limit reported, • Antihelium search reaching down to the upper limit ~3 x 10-7 • BESS-PolarII planned, and important for • Ultimately sensitive search for primordial antiparticle with the long duration flight in solar minimum in 2007, and • Further precise measurement of cosmic rays, in a complimentary approach to PAMELA and AMS.

  30. Cosmic-ray Antiprotons Observed by BESS 10-1 BESS(95+97) BESS(93) IMAX CAPRICE Pbar flux [m-2sr-1sec-1GeV-1] Solar Minimum 10-2 • More than 4000 antiprotons (candidates) observed 10-3 10-1 1 10 Kinetic Energy (GeV)

  31. BESS-Polar ●Trigger Configuration ★UL Trigger ★UM Trigger

  32. BESS-Polar II Cross Section

  33. TOF PMT Problem and Improvement of Housing ＰＭＴ－ＨＶ Both-end Single-end Dead 18/44 PMTs turned off due to low pressure discharge and excessive current Geometrical Acceptance limited to 67 % PMT housing to be improved by using pressure vessel as on BESS-Polar I ACC, instead of Resin Potting

  34. TOF PMT Problem and Improvement of Housing ＰＭＴ－ＨＶ Both-end Single-end Dead 18/44 PMTs turned off due to low pressure discharge and excessive current Geometrical Acceptance limited to 67 % PMT housing to be improved by using pressure vessel as on BESS-Polar I ACC, instead of Resin Potting

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