analysis of light single- hypernuclei events in nuclear emulsion detected with overall-scanning...
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Analysis of Light Single-L Hypernuclei Events in Nuclear Emulsion Detected with Overall-scanning Method
MYINT KYAW SOE, Kazuma NAKAZAWA, Kaoru HOSHINO, Hiroki ITO, Kazunori ITONAGA, Hidetaka KOBAYASHI, Yoko ENDO ,
Junya YOSHIDA, Khin T. TINT, Shinji KINBARA, Akihiro MISHINA
Introduction Review experiments for Life-
time of L3H
Outline
30/11/2014
Nuclear Emulsion
Searching 3LH hypernucleus
events in nuclear emulsion
Gifu UniversityJapan
Estimation of mesonic decay events Summary
Introduction
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L3H is the most basic and simple hypernuclear bound system among hypernuclei
n
L
pBL= 0.13 ±0.05 MeV
So far its life-time estimated by any experiments has large interval in each other
Life-time for L3H are estimated by experiments
In order to provide precise information of life-time and BL with small
error for L3H
high statistics events for L3H are requiered
Less than and nearly 180 ps
Aim is to measure the life-time and BL of light single- L hypernuclei with nuclear emulsion experiment
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Review experiments for Life-time of L3H
1) Counter experiments
HypHI collaboration [1] 6Li+12C at 2A GeV
Observed the life-time for L3H : 183+42
-32 ± 37 ps & for :L 262+56-43 ± 45ps
STAR at BNL RHIC [2]197Au+197Au
Observed lifetime for 3LH, 138+26-22 ps
Above two counter experiments inform the life-time of 3LH is shorter than that of free L and their estimation
interval is large
[1] C.Rappold et al. Nuclear Physics A913 (2013) 170-184
http://kds.kek.jp/getFile.py/access?contribId=18&sessionId=40&resId=0&materialId=slides&confId=15455[2]
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2) Emulsion experiment [3]
Emulsion stacks are exposed by 2.3 and 2.5 GeV/c2 K-
3LH → 3He + p- (3 in-flight and 1 at rest decays)
Observed the life-time for 3LH : 0.9+2.2
-0.4 ×10-10 s
If life-time of 3LH is shorter than free , L BL of 3
LH may be reconsidered
Life-time of 3LH(<=180 ps) should be nearly equal to that of ( 263L ps) because BL is very small
Expect to confirm information of life-time with many statistic events in nuclear emulsion
[3] R. J. Prem and P. H. Steinberg , Physical Rev. vol136,number 6 B, Dec,1964
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Nuclear Emulsion
Emulsion are composed of 8 materials and AgBr is the large amount of them
AgBr crystal
Microscopic image
The best detector for the short-life nuclei
The charged particle loss their energy according to the ionization along their ranges traveled in emulsion
Ranges can be transformed into Kinetic energy with
When charged particle passed through emulsion
After photographic developing
Latent image
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Searching 3LH hypernucleus events in nuclear emulsion
3LH → 3He + p- (two body decay)
3LH → 2H +1
1H + p- (three body decay)
p-
3LH
3He
p-
3LH
2H
11H
p-
3LH
3He
Inflight decay At-rest decay
Schematic topology of 3LH decay in emulsion
To get many statistics of 3LH events (more than 5×102 events)
Detect events in emulsion plates of KEK-PS E373 experiment by Overall-scanning method
presented by Dr. J. Yoshida
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Emulsion plate
Eye check events in 3 dimensions under microscope
X
y
z
Output images from overall-scanning
Automatic scanning
Event detection
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Event categorization
Single candidate events Uranium decayed series
Beam interaction Thorium decayed seriesHammer track And so on
By seeing topology of events, the event types are classified as
Among single hypernucleus events, mesonic decayed events for 3LH
have to choice
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Estimation of mesonic decay
Overall-scanning detect full volume of emulsion plates
Even the test scan of overall-scanning, we found the two mesonic decay events for candidates of L3H from (3cm×3cm) scan area
#1 #2
#3#4
#1
#3 #2
#4
We estimate mesonic decay events nearly 100 in one plate (25×24.5)cm2
Beam
Beam
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Construction of invariant mass
range, angle theta and phi of daughter particles
Kinetic energies &
momentum
Invariance Mass
Our measurement result will be checked with consistence of other experiments
From the measured invariant mass, range , momentum, BL and life-time are estimated
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Summary
Reviewed experiments for life-time of L3H, their estimation interval is large
To provide and confirm precisely BL and life-time of L3H, high statistics of
L3H candidates are searched
The emulsion plates of KEK-PS E373 experiment are detected with overall-scanning method
We estimate the mesonic decay events nearly 100 for the candidates of L3H in one emulsion plate
The precise information of Life time and BL of L3H will be estimated from the invariant mass constructed with emulsion data
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Measuring mass of single-L hypernucleus
• The mass of single hypernucleus can be constructed from momentum and energy of daughter fragments
Kinetic energy of daughter particles
Ranges of daughter particles in nuclear emulsion with range-
energy relation
Momentum of daughter particles
Image of single
candidate event
Before analysis, the range and energy should be calibrated
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Range-Energy Relation depend on density and shrinkage factor of nuclear emulsion plate
Calibrated by using monochromic a particles
Range-energy Calibration
shrinkage factor (S) =thickness of emulsion plate at beam exposure
thickness of emulsion plate at measurement
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Dz2 ( m
m2 )
Dx2+Dy2(mm2)
2222 SzyxR DDD
Range distribution of a particles decayed from 212Po
222222 /))(/1( SRyxSz DDD
Compare with linear equation,
Range of a particles as;
cmxy 2/1 Sm 22 / SRc
Where, S = shrinkage factor
S = 2.29 ± 0.01
R = 48.94±0.30mm
By using the well known energy 8.484MeV
Density of emulsion = 3.75 ± 0.14 g/cm3
Range→ Kinetic energy → momentum
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y
z
x
By fitting of the data points in linear on x-y plane and x-z as y = a x + b z = c x + dparameters a, b, c, d are obtained
The parameters are fitted by c2 liner fitting method
)(2)()( 01
02
0dEzDV t
By the use of constraints Hi= yi-axi-b
Hi= zi-cxi-d
Minimizing with respect to a, l and z
1)( EVEV Dt
E
0t
EEVz
Where;
d
c
b
a
z
zi
yi
xi
c
a21tan
c
a21arctan
atan
aarctan
Measuring angles q and f of tracks
Momentum, q, f of tracks are known15
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BL of single-L hypernucleus
From measured mass of sinlge-L hypernucleus, BL will be obtained as
XMΛMXMB AΛ
1AZΛ
The Life time (T) can be measured from the range (R) and momentum(P) as
T
R
p
M
Life-time of single-L hypernucleus
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Introduction
Aim is to measure BL and life-time of light single-L hypernuclei precisely with nuclear emulsion
So far the error of BL of light single- L hypernucleus such as L3H is large since the number of events is a few
Overall-scanning method detect full volume of emulsion plate (Already presented by Dr. J. Yoshida)
To search many number of single-L hypernuclear events, emulsion plates of KEK-PS E373 experiment are detected with overall-scanning method
Recently, counter experiment suggested the life-time of L3H is smaller than that of L hyperon
Life-time of L3H will be confirmed with nuclear emulsion experiment
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Summary
The emulsion plates of KEK-PS E373 experiment are detected with overall-scanning method to search many number of single hyper events
The mass of singe nucleus is measured from the kinetic energy and momentum of daughter fragments
Range and energy is calibrated with the tracks of alpha particle decayed in thorium and uranium series.
BL and life-time will be measured from the constructed mass , range and momentum of single hypernucleus in nuclear emulsion
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