The The p p K K++ and and p p KK++00 reactions reactions

at SPring-8/LEPSat SPring-8/LEPS

Mizuki SumihamaMizuki SumihamaRCNP, Osaka Univ.RCNP, Osaka Univ.

for the LEPS collaborationfor the LEPS collaboration

HYP2006 Oct. 13th 2006

Physics motivationPhysics motivation

It is essential to fully know It is essential to fully know NN** and and ** to understand to understand baryon structure.baryon structure.Many nucleon resonances Many nucleon resonances predicted by quark model predicted by quark model are are still missingstill missing..

DD1313(1900) (1900) resonanceresonance in in SAPHIR / CLAS data was SAPHIR / CLAS data was foundfound

K+

Y()p

N, N*, *

Some resonances should couple to K or Kchannel.Kaon photoproduction is good means

to search for missing resonances.

Missing resonances N* andMissing resonances N* and * * in s-channelin s-channel

Meson exchange in t-channelMeson exchange in t-channel

K+

Y()p

K*, K, K1

E = 1.5 2.4 GeVTransition region, s-channel t-

channelContribution of t-channel meson

exchangebecomes large above 2GeV.

Photon-beam asymmetry natural parity exchange (K*) = + 1unnatural parity exchange (K, K1) =－ 1 at t = 0 and large E.

LEPS spectrometer LEPS spectrometer – forward acceptance– forward acceptance

1m

TOFwall

MWDC 2

MWDC 3MWDC 1

Dipole Magnet (0.7 T)

Liquid HydrogenTarget (50 mm thick)

Start counter

Silicon VertexDetector

AerogelCherenkov

(n=1.03)

Linearly polarized

Particle identificationParticle identification by time-of-flight and momentum by time-of-flight and momentum

measurementsmeasurements

Momentum resolution ~0.8% for 2GeV/c Kaons. Time resolution ~150 ps.

KK++ Missing mass spectrum Missing mass spectrum

K+

p p K K++(1116) (1116) p p K K++00(1193(1193) )

Z-vertex distribution

LH2 target

Differential cross sections Differential cross sections –Energy dependence–Energy dependence

W (GeV)

Resonance-like structure

W (GeV)

K+K*-exchange by M. Guidal.Isobar + Regge by T. Mart and C. Bennhold. Gent isobar model by T. Corthals

LEPS　　　　 SAPHIR CLAS

0(1193)(1116)

Differential cross sections Differential cross sections - - angular dependenceangular dependence

No forward peaking.Can be explained by Feynman diagram only.

LEPS CLAS

0(1193)(1116)

Forward peaking cannot be reproduced By Feynman diagram only, at E> 2GeV.Need Regge poles.

Regge model K+K*-exchangeIsobar (Feynman) only Isobar + Regge by T.Mart and C.Bennhold.

Photon-beam asymmetry Photon-beam asymmetry

-single polarization observable-single polarization observable

K+K*-exchange by M. Guidal.Isobar + Regge by T. Mart and C. Bennhold. Gent isobar model by T. Corthals

data

Polarization observable is important in order to fix the model parameters (fine optimization) and understand the Kaon Photoproduction, including the existence of a missing resonance -D13???.

Positive sign

Differential cross sections Differential cross sections for for p p p p00

--Check photon normalization factorCheck photon normalization factor

LEPS dataOld dataCurves SAID(fit data at E < 2GeV)

Good agreement with SAID Photon normalization is OK.

Meson photoproduction in u-Meson photoproduction in u-channelchannel

0

Missing mass for p pX

We will obtain differential cross section and photon asymmetry for ’and.

Measure photon-beam asymmetry at backward angles where no data.

for for p p p p00

LEPS dataOld dataCurves SAID

Detect protons by forward spectrometer.

SummarySummaryThe KThe K+ + photoproduction was measured by linearly polarized photoproduction was measured by linearly polarized photons at SPring-8/LEPS. photons at SPring-8/LEPS. Photon-beam asymmetry is good tool to define theoretical Photon-beam asymmetry is good tool to define theoretical models.models.Differential cross sections were obtained at very forward Differential cross sections were obtained at very forward angles, up to cosangles, up to coscmcm = 0.975. = 0.975.Bump structure was seen at W=1960 MeV in the KBump structure was seen at W=1960 MeV in the K++ mode. mode. We see a forward peaking in KWe see a forward peaking in K++while no peaking in Kwhile no peaking in K++00..In order to fit the forward-angle data, a Regge pole is In order to fit the forward-angle data, a Regge pole is necessary in addition to s-channel resonances and t-channel necessary in addition to s-channel resonances and t-channel K and K*-exchanges. K and K*-exchanges. Combination of isobar (Feynman) and Regge is successful to Combination of isobar (Feynman) and Regge is successful to explain this forward peaking in Kexplain this forward peaking in K++..Photon normalization was checked by Photon normalization was checked by p p p p00 cross sections. cross sections.

The data show a good agreement with SAID. LEPS photon The data show a good agreement with SAID. LEPS photon normalization is OK. normalization is OK. Photon asymmetry data are obtained at backward angles. Photon asymmetry data are obtained at backward angles.

M. Sumihama et al. PRC73, 035214 (2006) M. Sumihama et al. PRC73, 035214 (2006) 　　　　　　 R.G.T. Zegers, M.Sumihama et al. PRL 91, 092001-1 R.G.T. Zegers, M.Sumihama et al. PRL 91, 092001-1

(2003). (2003).

LEPS collaborationLEPS collaborationD.S. Ahn, J.K. Ahn, H. Akimune, Y. Asano, W.C. Chang, S. Date, H. Ejiri, H. Fujimura, M. Fujiwara, K. Hicks, K. Horie, T. Hotta, K. Imai, T. Ishikawa, T. Iwata, Y.Kato, H. Kawai,

Z.Y. Kim, K. Kino, H. Kohri, N. Kumagai, Y.Maeda, S. Makino, T. Matsumura, N. Matsuoka, T. Mibe, M. Miyabe, Y. Miyachi, M. Morita, N. Muramatsu, T. Nakano, Y. Nakatsugawa, M. Niiyama, M. Nomachi, Y. Ohashi, T. Ooba, H. Ookuma, D. S. Oshuev, C. Rangacharyulu, A. Sakaguchi, T. Sasaki, T. Sawada, P. M. Shagin, Y. Shiino, H. Shimizu, S. Shimizu, Y. Sugaya, M. Sumihama H. Toyokawa, A. Wakai, C.W. Wang, S.C. Wang, K. Yonehara, T. Yorita, M.

Yosoi and R.G.T. Zegers, a Research Center for Nuclear Physics (RCNP), Ibaraki, Osaka 567-0047, Japan

b Department of Physics, Pusan National University, Pusan 609-735, Koreac Department of Physics, Konan University, Kobe, Hyogo 658-8501, Japan

d Japan Atomic Energy Research Institute, Mikazuki, Hyogo 679-5148, Japane Institute of Physics, Academia Sinica, Taipei 11529, Taiwan

f Japan Synchrotron Radiation Research Institute, Mikazuki, Hyogo 679-5198, Japanh School of physics, Seoul National University, Seoul, 151-747 Koreai Department of Physics, Ohio University, Athens, Ohio 45701, USA

j Department of Physics, Kyoto University, Kyoto, Kyoto 606-8502, Japank Laboratory of Nuclear Science, Tohoku University, Sendai 982-0826, Japan

l Department of Physics, Yamagata University, Yamagata, Yamagata 990-8560, Japanm Department of Physics, Chiba University, Chiba, Chiba 263-8522, Japan

n Wakayama Medical College, Wakayama, Wakayama 641-0012, Japano Department of Physics, Nagoya University, Nagoya, Aichi 464-8602, Japan

p Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japanq Department of Physics, University of Saskatchewan, Saskatoon, S7N 5E2, Canada

r Department of Applied Physics, Miyazaki University, Miyazaki 889-2192, Japan