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Experimental study of strange tribaryons in the reaction. Heejoong Yim Seoul National University For E549 collaboration. KEK-PS E549 Collaboration. - PowerPoint PPT Presentation
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Experimental study of strange tribaryons in the reaction
Heejoong YimSeoul National University
For E549 collaboration
),(4 nKHe stop
KEK-PS E549 CollaborationH. Bhang, J. Chiba, S. Choi, H. Fukuda, T. Hanaki, R. S. Hayano, M. Iio,
T. Ishikawa, M. Iwai, S. Ishimoto, T. Ishiwatari, K. Itahashi, M. Iwasaki, P. Kienle, J. Kim, Y. Matsuda, H. Ohnishi, S. Okada, H. Outa, M. Sato, S. Suzuki, T. Suzuki, D. Tomono, E. Widmann, T. Yamazaki, H. Yim
nucl-ex/0310018
higher statistics with better resolution is required to confirm the peak structure.
2
1,2
100 pST
2
1,2
1
3
2
2
1,2
3
3
1
2
1,2
11,10
1 pST
pSHeK stom )( 4
nSHeK atom )( 4
2
1,2
10
nST
2
1,2
1
3
1
2
1,2
3
3
2
2
1,2
10,11
nST
Difference between
),(4 nKHe stop ),(4 pKHe stop
and
No structure at around 3140 MeV/c2 on the proton spectrum
T=0
KEK PS-E549 experiment• Further study of S0 state in the 4He(K-
stop, p) reaction
• Search for other kind of strange tribaryon in the 4He(K-
stop, n)
(2) Inclusive spectroscopy of S0
(1) Determination width with high resolution
E471 upper limit E549 finite value
Statistics x 20
Formation rate
(3) Search for excited state
(2) Confirmation of S+ (T=0) (statistics ~3 times higher)
(1) Study of isospin dependence (T=0,1 state)
K- + 4He → S0[T=1] + p | 1/2 -1/2 > |1 -1> + |1/2 1/2>K- + 4He → S+[T=1] + n | 1/2 -1/2 > |1 0> + |1/2 -1/2>
Formation ratio = 2:1
- 4He(K-stop, p) spectroscopy
- 4He(K-stop, n) spectroscopy
TC
TC
NC
NC
T0
VDC
BLC
TOF analysis for neutral particles
0TTNCT
tkaon_flighT
NCtargetTOF
flightkaonTNCNCtarget TTTTOF _0
1. TNC-TT0
2. Determine vertex point TOFtarget->vertex
3. Tkaon_flight
K
Stopping kaon selection by T0 ADC
z
z
K -
K -
T0ADC (a.u.)
T0ADC (a.u.)
Stop kaon selection region
Target cellTarget region
Z
BLC
VDC
Target cellK
Beam direction
Zcos
σ ~295ps
σ ~380ps
Z-vertex correction for kaon flight time from T0 to it’s stop
NC ADC (MeVee)
1/b
eta
Separation for NC
n
n/
Previous result (E471) Present preliminary result (E549)
/1
S/N Improvement
Improvement
S/N ratio is much improved.
10 MeVee
3 MeVee
5 MeVee
n
n
NC time calibration and resolution
σ~0.040
Previous result (E471)
/1
Now the resolution is comparable with E471 result. But, TOF analysis is still progressing.
So, the resolution will be more improved.
Present E549 result (very preliminary)
10 MeVee threshold
E MeVee
The resolution variation on ADC energy range(10 MeVee threshold)
/1
~185MeV/c
nstopped
Check of neutron TOF analysis using Σ decay
Monochromatic neutron source from
is expected in the stopped K - reaction
at 185 MeV/c
We can say neutron momentum scale is
reasonable.
3MeVee threshold &
1 charged hit on TC &
1 charged hit on the opposite NC arm
3MeVee threshold &
1 charged hit on the opposite NC arm
~185MeV/c
Particle identification by TC
Previous TC setup (E471)
Present TC setup (E549)
CBE
dE/d
x of
TC_
A (a
.u.)
TC_D layer
TC_A layer
TC_C layer
TC_B layer Upgrade
TC_thin layer
(a.u.)
TC_thick layer
TC_thick MeVee/cm
TC_t
hin
MeV
ee/c
m
Semi-inclusive neutron momentum distribution
Previous result (E471)
7 MeVee threshold
10 MeVee threshold
Present result (E549)
summary
• Neutron S/N ratio is much improved.• Now, missing mass resolution is
comparable with previous E471 result.• Neutron statistics is increased.• Analysis is in progress.
z
y
z (mm)
Target cell
Carbon degrader
Al cap
y
x
Vertex image by VDC and BLC tracking
Degrader & Al cap
),(4 nKHe stopResult of previous experiment
E471 for Indication of strange trybaryon S+ (T=0)
Stopping kaon selection by reaction time
Reaction time of
100ps
),( XK
Zcos
reactionT
Reaction time of ),( XK
cLTTTT flightkaonTNCreaction /_0
Unit :100ps
reactionT
Blue : cut by stop kaon selection
Red : remainder after stop kaon selection
In-flight decay
stop decay
Beam direction cosine distribution of Decay particle by VDC chamber
7MeVee
Stop event Passing through event
PID by TC (2)
cMeV /
Blue : Accidental neutron
Red : After rejecting accidental neutron
With 10 MeVee threshold
NC ADC (MeVee)
1/b
eta
threshold
Accidental neutron
Cell structure of VDC