the bess program
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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The BESS Program
Akira Yamamoto (KEK) for the
BESS collaboration
SpacePart-06, Beijing, April 20, 2006
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
BESSCollaboration
The Universityof Tokyo
High Energy AcceleratorResearch Organization(KEK)
University of Maryland
Kobe University
Institute of Space andAstronautical Science/JAXA
National Aeronautical andSpace AdministrationGoddard Space Flight Center
University of Denver(Since June 2005)
BESS CollaborationAs of April, 2006
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BESSBalloon-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
5
BESS DetectorRigidity measurement
SC Solenoid (L=1m, B=1T)
Min. material (4.7g/cm2)
Uniform field Large acceptance
Central tracker (Drift chamber~200m
Z, m measurementR, --> m = ZeR 1/2-1dE/dx --> Z
JET/IDCRigidity
TOF, dE/dx
√
6
BESS-TeV Deflection ResolutionMDR 1.4 TV
BESS-98MDR 200 GV
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BESS-TeV Spectrometer
JET/IDC
MAGNET
TOF
ODC
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Progress of BESS Experiment
1993~ 2000, BESS, North Canada2002, BESS-TeV
2001, BESS-TeV, Fort Sumner
2004, BESS-Polar I, Antarctica
1999, 2001, BESS-Ground, Japan
10 scientific balloon flights during1993-2004
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Primary Cosmic-ray Spectra (1998: Bess-98, AMS-I, Caprice)
Sanuki et al. ApJ. 545 (2000) 1135
Error: < +/-5 % @ 100 GeV
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Primary Cosmic-ray Spectra (BESS-TeV)
Haino et al. PLB 594 (2004) 35
Error: < +/-15 %@ 500 GeV
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BESS-TeV Result Anchor the P and He Spectra in Low Energy (< TeV)
F = Ek-
Proton (Ek> 30 GeV) = (1.37 ± 0.12)x104
= 2.732 ± 0.022
Helium (Ek> 20 GeV)
= (7.06 ±
1.15)x102
= 2.699 ± 0.059
Fitting based on the BESS-TeV results only
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Low Energy Cosmic-ray SpectraPrecisely Measured by BESS
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.
10120.1
104
10-28
Flu
x (m
2 sr
s G
eV)-1
Energy (GeV)
BESS
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Search for Antiprotons of Cosmic Origins
• 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.
Primary Detectable
Secondary SUSYPBH
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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 Started1987: LEAP, PBAR (upper limits)1991: MASS1992: IMAX (16 antiprotons)1993: BESS (6 antiprotons), TS931994: CAPRICE94, HEAT-e
1996: Solar minimum1998: CAPRICE98, AMS-012000: HEAT-pbar2004: BESS-Polar2006: PAMELA 2007: Solar minimum, BESS-Polar2008: AMS-02 Before the BESS Experiment
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1979: First observation (Golden et al)
1979: Russian PM (Bogomolov et al)1981: Excess reported (Buffington et al)
1985: ASTROMAG Study Started1987: LEAP, PBAR (upper limits)1991: MASS1992: IMAX (16 antiprotons)1993: BESS (6 antiprotons), TS931994: CAPRICE94, HEAT-e
1996: Solar minimum1998: CAPRICE98, AMS-012000: HEAT-pbar2004: BESS-Polar2006: PAMELA 2007: Solar minimum, BESS-Polar2008: AMS-02 By the BESS Experiment
Annual Variation of P /P Ratio
10-6
10-5
10-4
10-3
10-1
1 10
(GeV)
Pñ/P ratio
Kinetic Energy
Bieber et al, 1999
10, ( +)~1997 . solar min at positive phase
70,(+)~1999 . solar max at positive phase
70,(−)~2000 . solar max at negative phase
. ., . . ., .Y Asaoka et al Phys Rev Lett in press
(97)BESS(99)BESS(00)BESS
p/p Ratio
BESS
Observation of Cosmic-rayAntiprotonsin p-bar/p Ratio
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BESS(95+97)BESS(93)IMAXCAPRICE
Kinetic Energy (GeV)10-1 1 10
Pb
ar
flu
x [
m-2sr-
1sec
-1G
eV
-1]
10-3
10-2
10-1
Low Energy Cosmic-ray Antiprotonsin last solar minimum (1995~97)
Mostly secondary particleswith specific peak at 2 GeV
Study:
Propagation model Solar modulation
Search for:
Novel Primary Origin?
(PBH, DM)
Flatter spectrum in low energy
More Statistics necessary ->> Long-duration Flight
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BESS-Polar Experiment
Very precise measurement Low energy Antiprotons
Around south-pole, Antarctica Long duration flight High latitude Solar minimumWith a new spectrometer Ultimately small material Ultra-thin superconducting solenoid
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Feature of BESS-Polar Spectrometer
Minimize material in spectrometerNew detector (Middle TOF)
Energy range extended down to 0.1 GeV
Low power electronicsSolar Power System, Longer life of cryogen, LHe Long duration flight
BESS-2000 BESS-PolarTOF Upper
Coil
JET/IDC
ACC
MTOF
TOF Lower18g/cm2
5g/cm2
10g/cm2
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BESS-Polar 20048.5 day flight successful35-37 km in altitude900 million events recorded - Acceptance limited to ~ 0.2 m2.sr
Altitude ~ 38000mResidual air ~ 4g/cm2
Floating
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Low Energy Antiproton Observed
in BESS Polar I (in 2004)
• ~ 2000 antiproton (total) candidate observed• ~ 400 antiprotons below 1 GeV
~ 2000AntiprotonCandidates
Preliminary
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Lowest Energy Events Observed
Limit by BTOF Trigger
★Kinetic Energy ~ 0.11GeV (@ TOA)
Antiproton event
★Multi-track events to be further studied
RGT -0.4GV1/β 2.47
Limit by MTOF Trigger
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Antiprotons Observed (Preliminary)
KineticEnergy(@TOA) BESS-97 Polar
0.1- 0.18 (GeV) - In Analysis
0.18-0.28 4 25
0.28-0.40 9 39
0.40-0.56 16 63
0.56-0.78 31 123
0.78-0.92 19 90
0.92-1.08 16 92
Total (below 1.08 GeV) 95 432
4~5 times statistics
(than that of 1997),
With ~0.2 m2sr (2/3),
8 days flight
Both-endSingle-endDead
PMT-HV
18/44 TOF-PMT turned-off
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Pbar/P Ratio Observation Extended
• The measurement consistent with the prediction, Bieber et al.
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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.
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Further Plan for BESS-Polar II
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
Record at Tiger flight
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Improvement toward BESS-Polar II
Subject (BESS-Polar I) (BESS-Polar II)
Magnet Cryogen Life ~ 11 days > 25 days
Track detector (JET) gas quality
~ 10 days > 20 days
TOF-PMT housing Resin potting Pressurized housing
ACC Particle ID Rejection ~ 630 >> 1000
Solar-power gen. 4 stage 900 W 3 stage 675 W
Effective Acceptance 0.2 m2sr 0.3 m2sr
Observation time 8.5 days > 20 days
StatisticsData storage
4 x BESS972 of 3.6 TB (recorded)
20 x BESS97 12 ~ 16 TB
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BESS Polar II Observation
(Expected)
Antiproton Spectrum Search for Antideuteron and AntiHelium(Search for PBH)
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BESS-Polar Feature
AMS02 PAMELA(10+20 days)
(3 years)
(3 years)BESS-Polar realize the best sensitivity in lowest energy
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350-600
280~500
Altitude
(km)
2007> 7520 days0.3BESS-Polar2
2006<70.43 years0.0021PAMELA
2008< 51.73 years0.5AMS
LaunchLatitude
Flight Time
Acceptance
(m2sr)
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Summary ■ BESS measured:
Precise Cosmic-ray Proton (Helium) spectrum with errors within 5 % @ 100 GeV, and 15 % @ 500 GeV with anchoring the spectrum at the lowest energy
Low energy Antiproton spectra 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-Polar II 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.
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Cosmic-ray Antiprotons Observed by BESS
• More than 4000 antiprotons (candidates) observed
0
1000
2000
3000
4000
5000
each yearintegrated
Year
Solar Minimum
BESS(95+97)BESS(93)IMAXCAPRICE
Kinetic Energy (GeV)10-1 1 10
Pb
ar
flu
x [
m-2sr-
1sec
-1G
eV
-1]
10-3
10-2
10-1
35
BESS-Polar
●Trigger Configuration
★UL Trigger ★UM Trigger
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BESS-Polar II Cross Section
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TOF PMT Problem and
Improvement of Housing 18/44 PMTs turned off due to low pressure discharge and excessive current Geometrical Acceptance limited to 67 %
Both-end
Single-end
Dead
PMT-HV
PMT housing to be improved by using pressure vessel as on BESS-Polar I ACC, instead of Resin Potting
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TOF PMT Problem and
Improvement of Housing 18/44 PMTs turned off due to low pressure discharge and excessive current Geometrical Acceptance limited to 67 %
Both-end
Single-end
Dead
PMT-HV
PMT housing to be improved by using pressure vessel as on BESS-Polar I ACC, instead of Resin Potting