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K + L and K + S 0 photoproduction at SPring-8/LEPS. Mizuki Sumihama Department of physics Osaka Univ. for LEPS collaboration 1. Introduction 2. Experiment 3. Data analyses 4. Experimental results - PowerPoint PPT Presentation
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K+and K+0 photoproduction at SPring-8/LEPS
Mizuki Sumihama
Department of physics Osaka Univ.
for LEPS collaboration
1. Introduction
2. Experiment
3. Data analyses
4. Experimental results
5. Summary
LEPS collaboration
M. Nomachi, A. Sakaguchi, Y. Sugaya, M. SumihamaDept. of physics Osaka Univ.
H. Fujimura, M. Fujiwara, T. Hotta, H. Kohri, T. Matsumura, N. Matsuoka, T. Mibe, M. Morita,
T. Nakano, R.G.T.ZegersRCNP Osaka Univ.
K. Imai, M. Miyabe, M. Niiyama, M. YosoiDept. of physics Kyoto Univ.
D.S. Ahn, J.K. AhnPusan Nat’l Univ.. Korea
T. IwataDept. of physics Yamagata Univ.
Y. Asano,N. MatsumuraJAERI
T. Ishikawa, H. ShimizuTohoku Univ.
H. Kawai, T. Ooba, Y. ShiinoChiba Univ.
S. Date, N. Kumagai, Y. Ohashi, H. Ookuma,
T. Yorita
JASRI
W.C. Chang, D.S. Oshuev, C.W. Wang,
S.C. Wang
Academia Sinica, Taiwan
A. WakaiAkita Industry Promotion Foundation
K. HicksOhio Univ.USA
C. RangacharyuluUniv.. of Saskatchewan Canada
H. AkimuneKonan Univ.
P. ShaginMinnesota Univ.
S. MakinoWakayama Med. Univ.
1. IntroductionMissing resonances N* and *in strangeness channels
• Information on nucleon resonances mainly comes from the N channel.
• Many nucleon resonances predicted by quark model are still missing.
• It is essential to fully know N* and * to understand the structure of baryons.
K+
Y()p
N, N*, *
Some resonances may couple to K or K channel.
K+ photoproduction is good means to search missing resonances.
Resonance structure?• Resonance like structure in the
total cross section for p(,K+) from SAPHIR and CLAS.
• Missing resonance D13(1960) ?
without D13
with D13
calculations by Mart and Bennhold
• There still remains a controversy
of the theoretical description.
• Only cross section data is not conclusive.
SAPHIR data
~ 1.9 GeV
Additional observables are required.
Photon beam asymmetry is one of the candidates.
Theoretical predictions of photon asymmetry
by Janssen et alby Mart & Bennhold
Hadronic form factor A B C Davidson&Workman Haberzettl
A) Small cut-off massB) * in u-channel C) No restriction on gKYp
without D13(1960)
with D13(1960)
With D13(1960)
Need more study to fix parameters.Photon beam asymmetry is sensitive to model differences.
2. Experiment• 2000.12 ~ 2001.6
• Liquid hydrogen target : 5cm
• Linearly polarized photons
Tagged photons 1.5 ~ 2.4 GeV
Resolution 15 MeV
Beam intensity 5 x 105 cps (Tagged photons)
High polarization ~92% at 2.4 GeV
~55% at 1.5 GeV
• 52% data with vertical polarization
48% data with horizontal polarization
• 2 x 1012 photons at the target
Photon beam asymmetries for the p(,K+) and p(,K+)0 reactions
3. Data analyses
• Tagged photons recoil electron by Tagging counter• Events from the proton target z-vertex point of K+
contamination from the trigger counter ~ 8% lab< 5o
< 2% lab> 5o
• K+ events mass distribution by tracking and TOF 2probability cut - confidence level 98% and proton contaminations ~ 2% • and 0events missing mass of p(, K+)X and 0contamination < 1%
Event selections for p(,K+)and p(,K+)0
Beam
Missing mass spectrum
• p(,K+)72,500
events• p(,K+)0 (1193)
48,900 events
• 1.5 ~ 2.4 GeV
• 0.6 < coscm < 1
Photon beam asymmetry
Photon beam asymmetry
• Vertical = [ 1 + Pcos(2) ]
• Horizontal = [ 1 - Pcos(2) ]
N = Facc
= Pcos(2)
• N : K+ photoproduction yield• : K+ azimuthal angle• P : Polarization of photon
• n : Normalization factor for Nv
ddv
ddunpol
ddunpol
ddh
dd
nNv - Nh
nNv + Nh
For all events
4. Experimental results
•Correction 1 & proton contaminations < 0.03•Correction 2 TRG contaminations< 0.02•Systematic error 1 from pol. degree & angle 1.5%•Systematic error 2 from normalization factor~ 0.03
•Positive sign•Different angular distribution •Increase as the E increases
p(,K+)
p(,K+)0
Comparison with models
Currently, no models
reproduce our data, perfectly.
by Mart & Bennhold
without D13(1960)with D13(1960)
by Janssen et al
Hadronic form factor A B C Davidson&Workman Haberzettl
A) Small cut-off massB) * in u-channel C) No restriction on gKYp
with D13(1960)
5. Summary• K+ photoproduction is good means
to search missing resonances.• Photon beam asymmetries were obtained
for the p(,K+) and p(,K+)0 reactions
at the first time in E= 1.5 ~ 2.4 GeV
at SPring-8/LEPS.
Positive sign• Our data will stimulate the further
development of the theoretical models
and extend our knowledge of this reaction including missing resonances.