2004.11.5 物質の創生と発展 1
Antiprotons in the cosmic radiation-- A brief history and some
recent results of BESS --
Mitsuaki NOZAKI(Kobe Univ.)
( ISAS/ KEK/ Kobe/ Maryland/ NASA/ Tokyo)
Antiprotons in the cosmic radiation
-- A brief history and some recent results of BESS --
Mitsuaki NOZAKI
(Kobe Univ.)
( ISAS/ KEK/ Kobe/ Maryland/ NASA/ Tokyo)
物質の創生と発展
We have been mesuring cosmic ray antiprotons for more than 10
years
And still trying to do a longer observation at Antarctica.
Today I am going to talk why there are so many things to
measure
about antiprotons.
Antiprotons in 1980s
Buffignton et al. reported
a very high flux that motivated many speculations on its origin
such as photino annihilation and
various propagation models.
物質の創生と発展
苦節６年
艱難辛苦を乗り越えて
物質の創生と発展
Balloon specific issues:
Weight & size
Power supply
Heat dissipation
Telecommunication
Mechanical robustness
One chance per year
物質の創生と発展
物質の創生と発展
With better TOF timing resolution
物質の創生と発展
BESS '97
With additional aerogel Chrenkov counter
物質の創生と発展
Ｄetection → Ｓpectrum
物質の創生と発展
Before → After
物質の創生と発展
物理のお話し
物質の創生と発展
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
and to gain the statistics we go to Antarctica.
Galactic secondary
Atmospheric secondary
Interstellar primary proton
Solar-modulated "primary" proton
~ 5 g/cm2 @ balloon altitude
lesc ~ 10 g/cm2
c
c
物質の創生と発展
Our final goal is to find some antirptons produced by these
exotic processes;
the evaporation of primordial black holes or the annihilation of
dark matter particles.
However, most of the antiprotons are considered to be produced
in our galaxy
by this normal hadronic interactions.
After the production by this process, antirprotons go on a long
journey.
They travel through the galaxy for several tens of million years
before reaching the solar system.
In the heliosphere, antiprotons are disturbed by the expanding
magnetic irregularities.
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
and to gain the statistics we go to Antarctica.
Galactic tertiary
Atmospheric tertiary
Galactic secondary
Solar-modulated galactic secondary (+tertiary)
+ Atmospheric secondary (~20% @ 5g/cm2)
c
c
物質の創生と発展
In the atmosphere, antiprotons interact with air nuclei by this
hadronic interaction.
And finally some of the survivors are detected by BESS or any
other cosmic ray detectors.
The secondary-produced galactic antirprotons may also interact
with istellar medium.
They may lose energy by inelastic interactons or may be
completely lost by annihilations.
We call them tertiary antiprotons.
So, if we want to find something news, all the ordinary
processes must be well-known.
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
and to gain the statistics we go to Antarctica.
Galactic secondary
Atmospheric secondary
Interstellar primary proton
Solar-modulated "primary" proton
~ 5 g/cm2 @ balloon altitude
lesc ~ 10 g/cm2
c
c
物質の創生と発展
Let me start with the energy spectrum of the primary
protons.
JET/IDCNmax2852pts
sx200150mm
ODCLtrack0.8 1.6m
MDR2001400GV
BESS-98 BESS-TeV
JET/IDC
ODC
物質の創生と発展
To measure high enrgy protons up to several hundred GeV, we have
refurbished the tracking system.
We have installed a new jet-type drift chamber with better
performance.
We added a pair of outer drift chambers outside the
solenoid.
The MDR has been increased from 200 to 1400 GV.
The tracking resolution is much better than the previous BESS
detector.
Phys. Lett. B594 (2004) 35-46
Proton Spectrum
At high energies (>30 GeV)
1 < E < 540 GeV
He nuclei have also been measured
in the energy range btw. 1 and 250 GeV/n.
物質の創生と発展
The energy spectrum was measured up to 540 GeV.
At high energies up to 100 GeV, the flux is consistent with our
previous measurement and also consistent with AMS.
However, in the low energy region, the solar modulation can not
be neglected.
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
and to gain the statistics we go to Antarctica.
Galactic secondary
Atmospheric secondary
Interstellar primary proton
Solar-modulated "primary" proton
~ 5 g/cm2 @ balloon altitude
lesc ~ 10 g/cm2
c
c
物質の創生と発展
We have measured the proton spectra almost annually.
Solar modulation
in preparation
At low energies
(Eth< E < ~20 GeV)
D(flux) ~ 10 - 40%
物質の創生と発展
From these measurements, from 1997 to 2002, we can derive an
interstellar spectrum,
which is used to calculate the galactic antirprotons.
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
and to gain the statistics we go to Antarctica.
Galactic tertiary
Atmospheric tertiary
Galactic secondary
Solar-modulated galactic secondary (+tertiary)
+ Atmospheric secondary
c
c
物質の創生と発展
I move on to antirprotons.
Antiproton at
solar minimum
secondary dominant
Phys. Rev. Lett. 84 (2000) 1078
galactic tertiary ?
Measurement ~ Calculation
The majority is galactic secondary
物質の創生と発展
This is the spectrum observed in the solar minimum period.
Due to the production kinematics and the sharply decreaseing
primary proton spectrum,
the secondary antiproton spectrum has this characteristic peak
around 2 GeV.
The BESS data show that the majorityof the cosmic ray
antiprotons is secondary.
In addition to the shape, the absolute value of the flux agrees
well with these calculations.
That means our propagation model is basically OK.
However, in the low energy region, there is some diffrence
between calculations.
The low statistics of the data can not tell which model is
better.
We first investigated the solar modulation effect on the
antiproton spectrum.
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
and to gain the statistics we go to Antarctica.
Galactic tertiary
Atmospheric tertiary
Galactic secondary
Solar-modulated galactic secondary (+tertiary)
+ Atmospheric secondary
c
c
物質の創生と発展
Solar modulation
Astropart.Phys. 16 (2001) 121 & Phys.Rev.Lett. 88 (2002)
051101-1
The drift model explains the ratio, but still needs to be
fine-tuned to reproduce the abolute. flux.
物質の創生と発展
This busy plot shows a compilation of our antiproton
measurements sinxe 1993.
The statistical error is large but we can see clearly the
modulation effect in the peak region.
If we take the ratio with the proton flux, the ratio is
well-reproduced by a dirft model rather tahn a spherical model.
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
and to gain the statistics we go to Antarctica.
Galactic secondary
Atmospheric secondary
Interstellar primary proton
Solar-modulated "primary" proton
~ 5 g/cm2 @ balloon altitude
lesc ~ 10 g/cm2
c
c
物質の創生と発展
I will show you some new results about the atmospheric
antiprotons.
I want to mention that these 2 production processes are similar
to each other except for target particles.
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
Purely atmospheric antiprotons have been measured below
geomagnetic cutoff.
Rcutoff (GV) / Ek (GeV)xair (g/cm2)
Ft. Sumner (2001)4.2 (3.4)4~26
Norikura (1999)11.2 (10.3)~742
KEK (1997)11.4 (10.5)~1000
c
c
物質の創生と発展
We have measured atmospheric antiprotons at 3 different
locations.
In 1999, we carried the apparatus to the top of Mt.Norikura.
Antiproton@乗鞍
Phys.Lett. B577 (2003) 10
H=2770 m
35 km from Kamioka
110 antiproton candidates
Tsukuba
Norikura
物質の創生と発展
Norikura is near the famous Kamioka mine.
Near the mountain top, there is a cosmic ray obseravatory.
We have detected 110 antiprotons.
PBH
To search for novel sources of antiprotons, known effects should
be "well-known",
Purely atmospheric antiprotons have been measured below
geomagnetic cutoff.
Rcutoff (GV) / Ek (GeV)xair (g/cm2)
Ft. Sumner (2001)4.2 (3.4)4~26
Norikura (1999)11.2 (10.3)~742
KEK (1997)11.4 (10.5)~1000
c
c
物質の創生と発展
In 2001, we went to Ft. Sumner, New Mexico.
BESS-2001
Flight at Ft.Sumner, NM
4 g/cm2
26 g/cm2
Phys.Lett. B564 (2003) 8
Rcutoff= 4.2 GV
物質の創生と発展
In this flight, the balloon lost altitude after reaching the
floating altitude.
The air thickness increased from 4 g to 26 g in 12 hours.
The geomagnetic cutoff is clearly seen in this proton
spectra.
Below this cutoff antiprotons are purely atmospheric.
物質の創生と発展
Antiprotons are identified by the time-of-flight measurement and
the aerogel chrenkov counters
with the refractive index of 1.022.
e/m contamination
Aerogel Cherenkov Counter
n=1.022
Rth(p) = 4.4 GV
Eth(p) = 3.6 GeV
eproton= 95.40.3%
Rejection factor = 7610
Contamination is largest
at the highest energy
~ 5% (Ft.Sumner)
~20% (Tsukuba)
物質の創生と発展
This distribution showsthe light output from the aerogel counter
for the relativistic particles.
The rejection factor for light particles is 7610 while keeping
the efficiendy at 95%.
Tsukuba (970-1010 g/cm2)
25 antiproton candidates
(0.4 - 3.4 GeV)
Ft.Sumner (4 - 26 g/cm2)
156 antiproton candidates
(0.2 - 3.4 GeV)
Atmospheric antiprotons
物質の創生と発展
We have detected 156 antiprotons below geomagnetic cutoff.
We also measured at KEK, Tsukuba in 1997.
At KEK, we have detected 25 antiprotons.
I sprod +sinel
II sprod+sinel (ann. only)
III sprod+sinel (ann. only)
IV sprod+sinel
V sprod +sinel (ann. only)
s(I) is based on S.A.Stephens, Astropart..Phys. 6 (1997) 229
s(V) is based on C.Y.Huang, PhD Thesis & Phys. Rev. D68
(2003) 053008
Model I~V : Calculated by K.Yamato, PhD Thesis
Model Comparison
4-26 g/cm2
994 g/cm2
I
II
III
IV
V
III
II
I
IV
V
物質の創生と発展
We compared our measuremets with some models.
Basically, we followed the calculation of Stephens published in
1997.
We used 2 different production cross sections and 2 diffrent
ineleastic cross sections.
One is taken from Stephens; with smaller production cross
section and larger inelastic cross setion,
and the other from Huang; with larger production cross section
and smaller inelastic cross section,
which includes only the annihilation.
I do not describe the details of their models.
The essential difference is the energy distribution of tertiary
antiprotons.
Stephens assumed a flat distribution.
Huang considers only annihilation, so the tertiary antiproton
has delta-function like distribution.
The other models assumes some combinations of their cross
sections.
If you look at this part, the smaller cross section seems to be
better,
but if you look at the low energy region, it seems that the
contribution fromt the annihilation is small.
Atmospheric antiprotons
at balloon altitude
at mountain
at ground
BG to galactic antiprotons
物質の創生と発展
This shows our 3 measurements and 2 calculations.
The smaller cross section from Stephens plus Huang's
annihilation-only interaction seems to explain the data.
The systematic error we quote for the background subtraction in
our previous publications
is shown by green shade which lies between model I and III.
The subtraction we made is based on the intermediate cross
sections.
将来計画
Primary proton/Helium flux
Galactic propagation
Sloar modulation
Atmospheric interaction
“普通のプロセス”の理解が深まった
もっと統計を！
物質の創生と発展
物質の創生と発展
BESS-Polar
Technical Flight at Ft. Sumner
Assembly at GSFC/NASA
物質の創生と発展
Nozaki Mitsuaki�Nozaki_Nikko.ppt�
