1/10
PID method for double strangeness nuclei
in nuclear emulsion
Shinji KINBARA
Phys. Dept., Gifu Univ., JAPAN
Collaborators
RIKEN
H.Ueno, Y.Ichikawa
Gifu Univ.
K.Nakazawa, J.Yoshida, K.T.Tint,
M.K.Soe, A.M.M.Theint , A.Mishina, Y.Endo,
H.Itoh, H.Kobayashi
Outline
1. Motivation
2. Test Experiment at RIKEN (NP1406 RRC-32)
3. Method for identification of decay daughter nuclei from double-L hypernuclei
3-1. Measurement of track width
3-2. Calibration of track width along the depth
4. Summary
2/10
1. Motivation
To understand L-L interaction,
it is necessary for unique identification of many double-L hypernuclei .
“NAGARA” event (KEK E373)
LL6
He was formed at point A, and sequential
weak decay was observed point B and C.
LL
6He
Ξ-
We expect to detect about one hundred
double-L hypernuclei in J-PARC E07
experiment.
3/10
1. Motivation
If track #2 is known to be triton, the mode A is identified,
and the excitation energy of 2.8 MeV is confirmed.
B.
If track #3 is identified as He (3He, 4He or 6He )，
the mode A is identified.
2． Test Experiment at RIBF RIKEN(NP1406 RRC-32)
■
4/10
8 isotopes (1H, 2H, 3H, 3He, 4He, 7Li, 9Be,11B)
RIPS secondary beam line has the best condition to get
8 isotopes within reasonable beam time.
■
Several incident angles ( θ = 0°
, 25°
, 50°
, 75°
)
5mm
Beam
θ
30mm
Emulsion
stack
Microscope images of Ξ-hyperons at 100 μm from stopping
points, where double-L hypernuclei were produced.
We measure track width depending on the angles (θ) along light axis.
■
Beam time : 2.5days (Dec.19~22, 2014)
3．Method for identification of decay daughter nuclei from
H He Li Be B C
N
double-L hypernuclei
5/10
O
We measure track width
in the emulsion.
Track width reflect dE/dx.
「宇宙線」小田稔著，裳華房(1985)p.113
-dE/dx [MeV/mg/cm2]
3.0
2.5
Ratio of energy-loss sum to 1H
For the coming experiment, we try to recognize 8 isotopes.
(1H+, 2H+, 3H+, 3He2+ ,4He2+ ,7Li3+, 9Be4+ and 11B5+)
20
15
2.0
1.5
1.0
0.5
0
100
10-1
101
102
Range from stopping point [mm]
10
5
0 0
10
101
102
Range from stopping point [mm]
Esum(11B) / Esum(1H) = 17
Esum(9Be) / Esum(1H) = 12
Esum(7Li) / Esum(1H) = 8
Esum(4He) / Esum(1H) = 4
We expect to separate
them well!!
Esum(4He) / Esum(3He) = 1.1
Esum(3H) / Esum(1H) = 1.6
Esum(2H) / Esum(1H) = 1.3
Challenge!!
3．Method for identification of decay daughter nuclei from
double-L hypernuclei
6/10
K.Nakazawa, et al., Ann. Rep. Tandem V.D.G.Lab. Kyoto Univ. 1996-1997 (1998) p.141
More than 15 years ago (1996), isotopes of 1H+ , 4He2+ and 7Li3+ were
exposed horizontally to the emulsion at Tandem V.D.G Lab. Kyoto Univ.
A superimposed image of
a track at focal planes.
Pick up edge of track with
image processing method.
We separated well 1H+, 4He2+ and
7Li3+ in use of 60 mm.
Good recognition
7/10
3-1. Measurement of track width
① Raw image
To uniform background
②ー①
② blurred image
F(x) = A*tanh(Gauss(x,μ,s))
is applicable to fitting both tracks.
Horizontal track
(Proton)
120
100
80
60
40
20
0
0
FWHM
brightness
brightness
Grain
(K-beam)
120
100
80
60
40
FWHM
20
0.4
0.8
1.2 1.6 2.0 2.4 [mm]
0
0 0.4
0.8 1.2 1.6
2.0 2.4 [mm]
3-2. Calibration of track width along the depth
We measured alpha track width and summed up track “Volume”
given by width from stopping point.
8/10
cross section of
emulsion plate
10
9
8
7
6
Average Volume [mm3]
Volume [mm3]
depth
5
4
3
2
1
0
2
4
6
8 10 12 14 16 18 20 22 24
Range from stopping point [mm]
10
9
8
7
6
5
4
3
2
1
0
2
4
6
8 10 12 14 16 18 20 22 24
Range from stopping point [mm]
3-2. Calibration of track width along the depth
9/10
We measured size of grain which a minimum ionization particle
forms because dE/dx should be same. Grain size should be same.
cross section of
emulsion plate
Base
14
12
10 0.49
8 ±0.04
6
mm
4
2
0
0.3 0.4
0.55
depth
It can be seen that grain size is different
along the depth .
±0.06 mm
For the calibration, we consider using grain
which minimum ionization particle forms.
0.5
0.6
0.7
0.8 [mm]
4． Summary
10/10
・ We try to recognize 1H+, 2H+, 3H+, 3He2+, 4He2+,7Li3+, 9Be4+ and 11B5+
in the emulsion at RIKEN (NP1406 RRC-32).
・ Summed energy-losses of He, Li, Be and B in the emulsion are
larger by 4, 8, 12 and 17 times than that of H, respectively.
・ The beam exposure will be run in December 2014.
・ We measured track width which is FWHM of brightness distribution
of vertical and horizontal tracks.
・ Alpha track “Volume” is different along the depth.
To calibrate that, we consider using grain which minimum ionization
particle forms.
3-2. Calibration of track width along the depth
Size of grain which forms track along the depth is different by
optical conditions and photographic development.
8/10
cross section of
emulsion plate
Base
14
12
10 0.49
8 ±0.04
6
mm
4
2
0
0.3 0.4
0.55
±0.06 mm
0.5
0.6
0.7
0.8
[mm]
depth
It can be seen that grain size is different
along the depth .
To calibrate that, we use beam tracks
Because beam momentum is enough high
(1.66GeV/c),thus dE/dx should be
the same through the emulsion.
This exp. ->Electron(650 MeV)@UVSOR
E07 exp. ->K-(1.7 GeV/c)@J-PARC
3．Method for identification of decay daughter nuclei from
double-L hypernuclei
R&D is ongoing
1. Measurement of track width
We consider track width from the FWHM of brightness
distribution of vertical and horizontal tracks.
2. Calibration of track width along the depth
Since the measurement of Alpha track width along the depth
is different, we calibrate by use of beam tracks.
3. Track width depend on incident angles
We have to make the calibration of track width.
7/11