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The Investigation of Strangeness Photoproduction in the Threshold R egion at LNS-Tohoku. Masashi Kaneta for the NKS/NKS2 collaboration Department of Physics, Tohoku University. 序. Introduction. Introduction. Motivation Understanding the mechanism of strangeness production - PowerPoint PPT Presentation
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The Investigation of Strangeness
Photoproduction in the Threshold Region
at LNS-TohokuMasashi Kanetafor the NKS/NKS2 collaboration
Department of Physics, Tohoku University
INTRODUCTION序
Introduction• Motivation
– Understanding the mechanism of strangeness production• via photoproduction on nucleon• focusing on neutral channel
• Characteristics– Neutral channel
• K + data is not enough to make a model to predict cross section of neutral channel
• K 0 data is the KEY of the study– Threshold region
• No resonance decay effect in the final products
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
3
Introduction• Motivation
– Understanding the mechanism of strangeness production• via photoproduction on nucleon• focusing on neutral channel
• Characteristics– Neutral channel
• K + data is not enough to make a model to predict cross section of neutral channel
• K 0 data is the KEY of the study– Threshold region
• No resonance decay effect in the final products
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
4
Introduction• Motivation
– Understanding the mechanism of strangeness production• via photoproduction on nucleon• focusing on neutral channel
• Characteristics– Neutral channel
• K + data is not enough to make a model to predict cross section of neutral channel
• K 0 data is the KEY of the study– Threshold region
• No resonance decay effect in the final products
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
5
Channels of Strangeness Production
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
g+p K++Lg+p K++S0
g+p K0+S+
g+n K0+Lg+n K0+S0
g+n K++S-
g+N K+Y
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The Cross-section
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Proton target
Mainly K+ data
Figure:PRC74(2006)044004
No databefore NKSexperimenthad started
Data: SAPHIRLines: Kaon-MAID
model
7
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Different predictions by Models
0.9 1.0 1.1 1.2 1.3 1.4 1.5
Eg [GeV]0.9 1.0 1.1 1.2 1.3 1.4 1.5
g+p K++L g+p K++L
g+n K0+L g+n K0+L
cosq
1.0
1.0-1.0
-1.0 0.0
0.0
s [m
b]
3
2
1
0
s [m
b]
10
5
0
ds/dW
[mb/
sr]
ds/dW
[mb/
sr]
0
0
1
1
Kaon-MAIDSaclay-Lyon A
Eg=1.05[GeV]
Eg=1.05[GeV]
Both models show similar results
Huge differences
8
Introduction• Motivation
– Understanding the mechanism of strangeness production• via photoproduction on nucleon• focusing on neutral channel
• Characteristics– Neutral channel
• K + data is not enough to make a model to predict cross section of neutral channel
• K 0 data is the KEY of the study– Threshold region
• No resonance decay effect in the final products
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
9
Introduction• Motivation
– Understanding the mechanism of strangeness production• via photoproduction on nucleon• focusing on neutral channel
• Characteristics– Neutral channel
• K + data is not enough to make a model to predict cross section of neutral channel
• K 0 data is the KEY of the study– Threshold region
• No resonance decay effect in the final products
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
10
MODELS模型
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
12
Theoretical Study: Effective Lagrangian Approach
• Hadron coupling– Isospin symmetry
• Electromagnetic (photo) coupling– Helicity amplitude
• Charged and neutral nucleon resonances
– Decay width• Charged and neutral Kaon resonances• However, the decay width of K1
resonance is not known
g
g
g
N
N
N
K
K
K
s channel
t channel
u channel
YNN*
K,K*,K1
Y
YYY*
g
N
KContact term
Y
- 0.45 in Kaon-MAID, estimated from gpK0S+ data Free parameter in SLA
53.1)()()( *
00** - g
ggKKgKKgKKr
)( 1 gKKr
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Models• Kaon-MAID
– T.Mart, C.Bennhold, PRC61 (2000) 012201(R)– Input: gpK+L, gpK+S0, gpK0S+
– Resonances: • N(1650) S11, N(1710) P11, N(1720) P13, • (1900) S31, (1910) P31 • K*(892), K1(1270)
– Hadronic form factor, contact term• Saclay-Lyon A
– T. Mizutani et al. PRC58 (1998) 75– Input: gpK+L– Resonances:
• N(1720) P13• L(1405), L(1670), L(1810), S(1660) • K*(892), K1(1270)
– No hadronic form factor
13
EXPERIMENTALSTUDY BY NKS/NKS2
実験
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
The NKS (1998-) and NKS2 (2004-) collaboration• Akita University, Akita, Japan
A. Sasaki• Ichinoseki National college of Technology, Ichinoseki, Japan
O. Konno• Department of Physics, Tohoku University, Sendai, Japan
N. Chiga, B. Beckford, M. Ejima, T. Fujii, Y. Fujii, T.Fujibayashi, T. Gogami, K. Futatsukawa,O. Hashimoto, K. Hosomi, K. Hirose(a), A. Iguchi, S. Kameoka, H. Kanda, M. Kaneta, H. Kato,D. Kawama, T. Kawasaki, C. Kimura, S. Kiyokawa, T. Koike, T. Kon, Y. Ma, K. Maeda,N. Maruyama, A. Matsumura, Y. Miyagi, Y. Miura, K. Miwa, S.N. Nakamura, H. Nomura, A. Okuyama, A. Ohtani, T. Otani, M. Sato, A. Shichijo, K. Shirotori, T. Takahashi(b), H. Tamura, N. Taniya, H. Tsubota, K. Tsukada(c) N. Terada, M. Ukai(d), D. Uchida,T. Watanabe, T. Yamamoto, T. Yamamoto, H. Yamauchi, K. Yokota
• Laboratory of Nuclear Science, Tohoku University, Sendai, JapanT. Ishikawa, T. Kinoshita, H. Miyahara, T. Nakabayashi, H. Shimizu, K. Suzuki, T. Tamae, T. Terasawa, H. Yamazaki
• Department of Nuclear Science, Lanzhou University, Lanzhou, ChinaY.C. Han, T.S. Wang
• Nuclear Institute, Czech RepublicP. Bydzovsky, M. Sotona
15
Student name is shown with underline(a)Now at LNS, Tohoku University, Japan(b)Now at KEK, Japan(c)Now at RIKEN, Japan(d)Now at Gifu University, Japan
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Laboratory of Nuclear Science (LNS), Tohoku Univ. at Sendai
• Electron beam up-to 1.2 GeV• Two tagged-photon beam lines
– Bremsstrahlung– Eg=0.8-1.1 GeV (from Ee=1.2 GeV)– Tagged-photon beam rate > ~MHz
16
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Tagged Photon System
BM4 tagger
BM5 tagger
to the otherexperimental hall
NKS2
Radiator (Carbon wire) to make Bremsstrahlung
B
Photo
n Bea
mEl
ectro
n (1.2
GeV
)
Scattered electron (0.1-0.4 GeV)
Tag F
Tag B
17
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Experimental Study at LNS, Tohoku• Neutral Kaon Spectrometer (NKS)
– The first measurement of the K0 cross section near the threshold• Published as PRC78(2008)014001
– The data prefers SLA model rather than Kaon-MAID• Backward peak in cos qCM distribution
• NKS2– Expanding the study using new spectrometer– Improving the acceptance
• K0, L single measurement• K0L coincidence measurement
– But the statistics is not enough• Detector upgrade project in progress
18
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Results of NKS
• The cross section of K0
– Eg =0.9-1.0 and 1.0-1.1 GeV– cos qKLab = 0.9-1.0
• The data prefer SLA– SLA suggests backward peak of K0 in CM
forwardbackward forwardbackward
19
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
NKS to NKS2
• Extending the study– We needed new spectrometer
• Larger acceptance• better TOF resolution for the particle
identification– The second generation of study by
Neutral Kaon Spectrometer 2 (NKS2)
20
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
NKS NKS2
Improved Acceptance by covering forward region
NKS to NKS2
21
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Particle Identification of NKS2• An example
– Liq. D2 target– two-tracks event– TOF resolution
~350ps– opening angle cut
is applied to reduce e+e-
• -0.9 < cosqOA < 0.8
22
TOF(IHL2-OHVL4)
char
ge si
gn pp
p-
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Decay Vertex Distribution
23
g
Vacuumcellregion
Target Cell
Opening angle cut -0.9<cosqOA<0.8is required
Target Cell
Decay vertex point [cm]
num
ber o
f cou
nts
• Decay vertex is reconstructed from trajectories of positive and negative charged particle pair
This distribution is projectedon beam axis direction
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Recent Results (K 0)• K0
S cross-section on Liq. D2 target– analyzed ~30% of recorded data– g+nK 0S+L is dominant– expanding angle
• New region: cos qKLab<0.9– Capability to discuss angular
dependence
24
0.9<Eg<1.0 [GeV] 1.0<Eg<1.1 [GeV]
K 0 momentum [GeV/c]
ds/d
p [m
b c/
GeV]
Background is estimated by side-bands
pp- invariant mass
0.0
-0.2
0.2
0.4
0.6
0.8
0.0 0.2 0.4 0.6 0.0 0.2 0.4 0.6
0.0
-0.2
0.2
0.4
0.6
0.8
0.0
-0.2
0.2
0.4
0.6
0.8
0.0
-0.2
0.2
0.4
0.6
0.8
0.0
-0.2
0.2
0.4
0.6
0.8
1.0
0.0
-0.2
0.2
0.4
0.6
0.8
1.0
cos K
Lab
0.8
- 0.9
0.7
- 0.8
0.9
– 1.0
Prelim
inary
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Recent Results (L)• L cross-section on
Liq. D2 target– Analyzed ~30% of
recorded data– g+n K0
S+L and– g+p K++L are
dominant
25
0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2
L momentum [GeV/c]
cosq
LLa
b0.
90 -
0.95
0.80
- 0.
900.
95 –
1.00
0.9<Eg<1.0 [GeV] 1.0<Eg<1.1 [GeV]
Background is estimated by side-bands
pp- invariant mass
Preliminaryds
/dp
[mb
c/Ge
V]
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Recent Results (cont’)• K 0 measurement
– Extends the study to discuss cosq dependence– Total number of the particle is similar to NKS
• statistics in each (Eg, p, cosq) bin are smaller.. • L measurement
– Large statistics (>10 times of NKS)– Data is from two reaction (g+p and g+n )
• need to separate to compare a model of elementally process
• K +L coincidence measurement– Four-track-event analyses– Need to increase the acceptance
• Detector upgrade project is on going
26
pp- Invariant Mass [GeV/c2]
pp- I
nvar
iant
Mas
s [G
eV/c
2 ]
all of combinationsfrom ppp-p- event
WHAT IS THE NEXT?
次
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
The next stage of the study• KY coincidence measurement
– No Fermi motion correction of n in d– Reaction plane will be defined
• More information for study– Self polarization of L
• New inner detectors– to increase the acceptance
28
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
L Polarization Measurement
qqq
cosP 1 )A(cos )(cos 0 LN
ddN
Acceptance as a function of cosq decay parameter
0.642(PDG)
polarization
pg
pLt = pg×pL t
LCM
q
pp
pp
Transverse polarization measurement
pK
qK
reaction planein CM
pN
29
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Model Predictions: L Polarization
q of Kaon in CM [degree]
L P
olar
izatio
nSLA
(rKK=
-2.0
87)
Kaon
MAI
DSA
1(P.
Byd
zolv
ski)
g+p K ++L g+n K 0+L
calculated by P. Bydzofvky
30
NEW DETECTORS
新
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
NKS2+ Set-up with New Inner Detectors
A 3D trackerVertex Drift Chamber
Inner Hodoscope
Upgrade project
NKS2 to NKS2+
32
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Acceptance for K 0
S+L Events
• The acceptance will increase with the same trigger condition– ~8 times
(1): all K0S (p+ p- )+Lp-p) events
(2): the four daughters pass through VDC with two OH Hits
(3): four daughters pass through OH Note: No decay volume cut is applied
L p p- channel)K 0
S (p+ p- channel)
Note: single tracking efficiency: assumed to be 90%
Acceptance of new detectorsAcceptance of Current Detectors
33
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
34
Vertex Drift Chamber Design• Requirements
– As possible as small cell• but limited by feedthrough
(f3mm)– At least 6 layers with stereo
wires• Decision
– Trapezoid (almost square) cell shape
– Half cell size: 4 mm– 8 layers– uu’ vv’ uu’ vv’
• increasing stereo angle with radius:6.0 - 11.1°
– Drift gas = Ar:Ethane(50:50)
55 mm
65 mm
137 mm
uu’uu’vv’
vv’
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Vertex Drift Chamber
• >99% tracking efficiency for each layer– by Cosmic-ray test, using Ar:Ethane (50:50) gas
• Position resolution: ~400 mm (FWHM)35
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Event Display
36
g beam
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Event Display
37
g beam
SUMMARY結
Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University
Summary• Investigation of Strangeness photoproduction
– focusing on the neutral channel: g+nK0+L– near the threshold
• using tagged photon beam (Eg=0.8-1.1GeV) Laboratory of Nuclear Science, Tohoku University
• KY coincidence measurement will open the next stage of the study
• Detector upgrade project is on going
39
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