( b alloon-borne e xperiment with s uperconducting s pectrometer)
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RCCN International Workshop sub-dominant oscillation effects in
atmospheric neutrino experiments 9-11 December 2004, Kashiwa Japan
Input data to the neutrino flux calculation :
Primary cosmic ray fluxes at various solar activities
Yoshiaki Shikaze (JAERI) for the BESS Collaboration
(Balloon-borne Experiment with Superconducting Spectrometer)
RCCN International Workshop sub-dominant oscillation effects in
atmospheric neutrino experiments 9-11 December 2004, Kashiwa Japan
Input data to the neutrino flux calculation :
Primary cosmic ray fluxes at various solar activities
Yoshiaki Shikaze (JAERI) for the BESS Collaboration
(Balloon-borne Experiment with Superconducting Spectrometer)
Balloon
To high altitude
BESS spectrometer to be lunched
Spectrometer Contents
1. Motivation
2. Spectrometer and Observations
3. Correction of Atmospheric Secondary Protons
4. Obtained Spectra at the Top of the Atmosphere
5. Solar modulation effects
6. Summary
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Climax neutron monitor & Sunspot number
Motivation : Solar activity
Solar minimum Solar maximum
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To understand the solar modulation, it is important to know time variation of low energy proton flux precisely.
For the precise measurement by balloon experiment (at
5g/cm2 ), we must estimate the contamination of the atmospheric secondary protons, because as the energy decrease, secondary protons increase rapidly.
Motivation : for low energy flux below 1GeV
To understand the solar modulation, it is important to know time variation of low energy proton flux precisely.
Solar Modulation
Precise Low energy P flux
Atmospheric secondary P
Secondary-to-primary ratio of proton flux at air depth of 5g/cm2 (Estimation results in Papini et al.)
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To understand the solar modulation, it is important to know time variation of low energy proton flux precisely.
For the precise measurement by balloon experiment (at
5g/cm2 ), we must estimate the contamination of the atmospheric secondary protons, because as the energy decrease, secondary protons increase rapidly.
For the secondary estimation, we can measure the cosmic-ray data during ascending and descending periods and can use the data at different air depths for the tune of the secondary calculation (using transport equations; Papini et al.).
Motivation : for low energy flux below 1GeV
To understand the solar modulation, it is important to know time variation of low energy proton flux precisely.
For the precise measurement by balloon experiment (at
5g/cm2 ), we must estimate the contamination of the atmospheric secondary protons, because as the energy decrease, secondary protons increase rapidly.
Solar Modulation
Atmospheric secondary P
Precise Low energy P flux
secondary P estimation
BESS-99,2000 … ascent data (Cutoff Rigidity~0.4GV)
BESS-2001 … descent data (Cutoff Rigidity~4.2GV).
The observed data below the cutoff is pure atmospheric secondary protons.
Ascent and descent data
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Features
1. Large Acceptance of 0.3m2Sr
2. Compact and Simple Cylindrical Structure
⇒ High statistics & Small systematic error
3. Uniform magnetic field of 1T
Proton selection
β-band cut (after dE/dx-band cut)
4. PID by mass measurement
Tracker (in B=1T) R = pc/Ze
50ps TOF counter dE/dx, β
BESS Spectrometer
Mass = ReZ(β-2 - 1)1/2
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Balloon Observations
Flight Map of BESS Summary of BESS-2000
Pressure
Altitude
Live time~2.1h
Live time~30.5h
( BESS-97~2000,2002 Cutoff
Rigidity~0.4GV)
Ft.Sumner
Lynn Lake
( BESS-2001
Cutoff Rigidity~4.2GV)
~1000km
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Correction of Atmospheric Secondary Protons
Secondary proton calculation (Papini et al.) based on transport equations
A B
C
D
E
F
2nd-p production processes
A. Evaporation
B. Recoil
C. Slowing down
D. Spallation
E. Interaction loss
F. Ionization energy loss
loss processes
Comparison of the calculation with observation
5.82g/cm2
11.9g/cm2
Primary
Secondary (Papini et al.)
Total (=primary +secondary ; Papini et al.)
BESS-2001 Observed data ( Abe et al. )
Cutoff effect
Primary
Secondary
(Secondary Only)
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Tune recoil generation function to agree with the observed proton data.
Correction of Atmospheric Secondary Protons
Secondary proton calculation (Papini et al.) based on transport equations
modified
[BESS-2001 at Ft. Sumner (cutoff rigidity~4.2GV)]
Comparison of the calculation with observation
5.82g/cm2
11.9g/cm2
Primary
Secondary (Papini et al.)
Total (=primary +secondary ; Papini et al.)
Cutoff effect
BESS-2001 Observed data ( Abe et al. )
A B
C
D
E
F
2nd-p production processes
loss processes
A. Evaporation
B. Recoil
C. Slowing down
D. Spallation
E. Interaction loss
F. Ionization energy loss
Comparison of the calculation with observation
5.82g/cm2
11.9g/cm2
Primary
Total (=primary +secondary; Papini et al.)
BESS-2001 Observed data ( Abe et al. )
Cutoff effect
Secondary (Papini et al.)
Total (This work)
Secondary (This work)
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Tune recoil generation function to agree with the observed proton data.
Correction of Atmospheric Secondary Protons
Secondary proton calculation (Papini et al.) based on transport equations
modified
[BESS-2001 at Ft. Sumner (cutoff rigidity~4.2GV)]
Comparison of the calculation with observation
5.82g/cm2
11.9g/cm2
Primary
Total (=primary +secondary; Papini et al.)
BESS-2001 Observed data ( Abe et al. )
Cutoff effectTotal (This work)
Secondary (Papini et al.)
Secondary (This work)
Recoil proton generation function
Our detectable energy range
Papini et al.
This work
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Correction of Atmospheric Secondary Protons
Growth curve (Air depth dependence) of proton flux at Lynn Lake
[Cutoff R~0.4GV]
Estimation as Primary + Secondary
This work
Papini et al.Observed proton data
(BESS-2000 ascent data at Lynn Lake)
Kinetic Energy region: 0.29-0.34(GeV)
This work
Papini et al.Observed proton data
(BESS-2000 ascent data at Lynn Lake)
Kinetic Energy region: 0.63-0.73(GeV)
Start from floating level
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Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002
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Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002
Kinetic Energy per Nucleon
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Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002
Kinetic Energy per Nucleon Kinetic Energy per Nucleon
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Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002
Proton fluxProton fluxProton fluxProton fluxProton fluxProton flux
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Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002
(He flux) x 1/10(He flux) x 1/10(He flux) x 1/10(He flux) x 1/10(He flux) x 1/10(He flux) x 1/10
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Solar modulation effects on our obtained data Force Field Approximation (1 parameter; Modulation parameter φ)
I(Ek,r1AU ) = I(Ek+φ,rb ) x (Ek+m)2 – m2
(Ek+φ+m)2 - m2
I(r) / p(r)2 = I(rb ) / p(rb )2,
E(r) = E(rb ) - φ
I(r) / p(r)2 = I(rb ) / p(rb )2,
E(r) = E(rb ) - φ
(ref. Φ~500MV for BESS-97 in Myers et al. )
BESS-97 proton
Interstellar Proton Flux = Aβ R P1 -P2
demodulate Φ~500MV
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Solar modulation effects on our obtained data
fitting for Φ
obtained by fitting
(ref. Φ~500MV for BESS-97 in Myers et al. )
Force Field Approximation (1 parameter; Modulation parameter φ)
I(Ek,r1AU ) = I(Ek+φ,rb ) x (Ek+m)2 – m2
(Ek+φ+m)2 - m2
Interstellar Proton Flux = Aβ R P1 -P2
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Summary
• To understand the solar modulation, it is important to know
time variation of low energy proton flux precisely.
• Low energy proton and helium spectra at a different solar activities
during a period of solar minimum, 1997, through post-maximum, 2002
have been measured by BESS.
•Their spectra at TOA were obtained
by using the calculation of atmospheric protons
revised to agree with the observed protons at different air depths.
•The obtained spectra were consistent with other experimental data of
cosmic-ray measurements.
•From the check of the solar modulation effects, Interstellar Proton spectrum was obtained by assuming a) Force Field Approximation, b) φ=500MV for BESS-97 and c) simple spectrum formula with 3 parameters.
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Thank you !