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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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akira yamamoto kek for the bess collaboration spacepart 06 beijing april 20 2006
Akira Yamamoto (KEK)

for the

BESS collaboration

SpacePart-06, Beijing, April 20, 2006

The BESS Program
outline
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
slide3
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)

slide4
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
bess detector
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

bess tev spectrometer
BESS-TeV Spectrometer

TOF

ODC

MAGNET

  • JET/IDC
progress of bess experiment
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

primary cosmic ray spectra 1998 bess 98 ams i caprice
Primary Cosmic-ray Spectra (1998: Bess-98, AMS-I, Caprice)

Error: < +/-5 %

@ 100 GeV

Sanuki et al. ApJ. 545 (2000) 1135

primary cosmic ray spectra bess tev
Primary Cosmic-ray Spectra (BESS-TeV)

Error: < +/-15 %

@ 500 GeV

Haino et al. PLB 594 (2004) 35

bess tev result anchor the p and he spectra in low energy tev
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)
low energy cosmic ray spectra precisely 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.

104

  • BESS

Flux (m2 sr s GeV)-1

10-28

0.1

1012

Energy (GeV)

Low Energy Cosmic-ray SpectraPrecisely Measured by BESS
slide13
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.
slide14
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

slide15
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

low energy cosmic ray antiprotons in last solar minimum 1995 97
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

bess polar experiment
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
slide18
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

slide19
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
low energy antiproton observed in bess polar i in 2004
Low Energy Antiproton Observedin BESS Polar I (in 2004)

Preliminary

~2000

Antiproton

Candidates

  • ~ 2000 antiproton (total) candidate observed
  • ~ 400 antiprotons below 1 GeV
slide21
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

antiprotons observed preliminary
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

pbar p ratio observation extended
Pbar/P Ratio Observation Extended
  • The measurement consistent with the prediction,

Bieber et al.

progress in antihelium search
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.
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

Further Plan for BESS-Polar II

Record at Tiger flight

bess polar ii observation expected
BESS Polar II Observation(Expected)

Antiproton Spectrum Search for Antideuteron and AntiHelium

(Search for PBH)

bess polar feature
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

summary
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.
cosmic ray antiprotons observed by bess
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)

slide32
BESS-Polar

●Trigger Configuration

★UL Trigger

★UM Trigger

tof pmt problem and improvement of housing
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

tof pmt problem and improvement of housing1
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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