( B alloon-borne E xperiment with S uperconducting S pectrometer)

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

Climax neutron monitor & Sunspot number

Motivation : Solar activity

Solar minimum Solar maximum

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.)

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

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

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

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)

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)

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

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

Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002

Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002

Kinetic Energy per Nucleon

Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002

Kinetic Energy per Nucleon Kinetic Energy per Nucleon

Proton and Helium Spectra at the Top of the Atmosphere from 1997 to 2002

Proton fluxProton fluxProton fluxProton fluxProton fluxProton flux

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

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

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

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.

Thank you !