Differential cross sections for K + photoproduction at SPring-8/LEPS.
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Transcript of Differential cross sections for K + photoproduction at SPring-8/LEPS.
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Differential cross sections for K+ photoproduction
at SPring-8/LEPS.
Mizuki SumihamaDepartment of physics
Tohoku university
For LEPS collaboration
JPS meeting at Kochi 9.27 2004
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The LEPS collaboration
Research Center for Nuclear Physics, Osaka University
D.S. Ahn, M. Fujiwara, T. Hotta, K. Kino,
H. Kohri, T. Matsumura, T. Mibe, T. Nakano, A. Shimizu,
M. Sumihama
Pusan National University
J.K. Ahn
Konan University
H. Akimune
Japan Atomic Energy Research Institute / SPring-8
Y. Asano, N. Muramatsu
Institute of Physics, Academia Sinica, Taiwan
W.C. Chang, T.H. Chang, D.S. Oshuev, C.W. Wang, S.C. Wang
Japan Synchrotron Radiation Research Institute (JASRI)
/ SPring-8
S. Date, H. Ejiri, N. Kumagai, Y. Ohashi, H. Ookuma,
H.Toyokawa, T. Yorita
Ohio University
K. Hicks
Kyoto University
K. Imai, M. Miyabe, M. Niiyama, T. Sasaki, M. Yosoi
Chiba University
H. Kawai, T. Ooba, Y. Shiino
Yamagata University
T. Iwata
Wakayama Medical University
S. Makino
Nagoya University
T. Fukui
Osaka University
H. Nakamura, M. Nomachi, A. Sakaguchi, Y. Sugaya,
University of Saskatchewan
C. Rangacharyulu
Institute for High Energy Physics (IHEP), Moscow
P. Shagin
Laboratory of Nuclear Science, Tohoku University
H. Shimizu, T. Ishikawa
University of Michigan
K. Yonehara
Michigan State University
R.G.T. Zegers Seoul National University
H. Fujimura Miyazaki University
T. Matsuda, Y. Toi
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• Missing baryon resonance search (D13, ….)
• Meson exchange in t-channel (K, K*, K1)
Physics motivations
Data of Kaon photoproduction at sub-GeV energy Cross section from SAPHIR, CLAS Recoil polarization from SAPHIR, CLAS Photon beam asymmetry from LEPS
E = 1.5 - 2.4 GeV at LEPS
There still remains a controversy in theoretical descriptions.
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Discrepancy between Bonn/SAPHIR and Jlab/CLAS
It is important to solve the discrepancy between SAPHIR and CLAS, and obtain the data overall energy and angle range.
+ p K+ + + p K+ +
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Experiment
• Photon energy 1.5 – 2.4 GeV.
• Liquid hydrogen target with a 5 cm.
• ~1x1011 photons at the target.
• K+ angle cos(cm) = 0.75, 0.85, 0.925, 0.975.
+ p K+ + (2.2x104 events) + p K+ + (1.5x104 events)
Detected by spectrometer.
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Event selection1 K+ selection with Mass (3). 2 Reject decay-in-flight with of track fitting.3 Reject e+e- cut (remove events in-plane). 4 Proton selection with z-vertex point. 5 Photon selection at tagging counter. 6 Hyperon selection with missing mass (2).
Data analysis
+ p K+ + + p K+ +
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d(coscm)a(NK+ - b)d
NB ・ NT ・ d(coscm)=
Differential cross sections
NK+ : number of selected K+ eventsNB : number of protonsNT : number of photons a = acceptance of K+ and detectors b = background contaminations (pions, protons, start counter) < 2.2% < 6.5%
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Results of differential cross sections
+ p K+ + + p K+ +
SAPHIR CLAS LEPS
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Theoretical models I
+ p K+ + + p K+ +
K + K* and K* : Regge theory by Guidal (NPA627, 645,1997)
Isobar model with missing resonance of D13 (PRC65,015201, 2002)
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Theoretical models II
+ p K+ + + p K+ +
Regge, Feynman (D13), Mix by Bennhold and Mart
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Theoretical models III
+ p K+ + + p K+ +
Regge, Feynman (D13), Mix by Bennhold and Mart
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Summary• Differential cross sections of K+ photoproduction at E = 1.5 – 2.4 GeV and forward angles.• LEPS data shows a good agreement with CLAS data.
Solve the discrepancy between SAPHIR and CLAS.• Resonance structure at W=1.86 GeV and forward peaking can be seen in + p K+ + . No resonance nor forward peaking in + p K+ + .• Refitting with new LEPS data and CLAS data and LEPS photon asymmetries data.
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LEPS detector
1m
TOFwall
MWDC 2
MWDC 3
MWDC 1
Dipole Magnet (0.7 T)
Liquid HydrogenTarget (50mm thick)
Start counter
Silicon VertexDetector
AerogelCerenkov(n=1.03)
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Photon beam asymmetry