11

K+ Photoproduction and p0

photoproduction by Linearly Polarized Photons at SPring-8/LE

PS

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

for the LEPS collaborationfor the LEPS collaboration MENU2007 Sep. 2007

8 GeV ring

22

Diagram of KDiagram of K++ / / pp00 photoproduction photoproduction

K+ (p

pp

N, N*, *

K+ (p0)

pp

K, K*, K1)

K+ (p0)

(pp

, Y*(N,N*)

ss-channel tt-channel uu-channel

Intermediate angle forward angle 　 backward angle

Spectrometer acceptance : 0.7<coscm <1

LEPS spectrometer covers the region where other facilities cannot access.

Forward data Forward data Detect K Detect K++, ID , ID 00 in missing mass in missing massBackward data Backward data Detect Detect (p(ppp, ID K, ID K++ in missing mass. in missing mass.

33

It is essential to fully characterize N* and * to understand baryon structure.

Many nucleon resonances predicted by quark model are still not observed.

Some resonances could couple to K or K channel.

Many one or two star resonances, above 1700 MeV (W > 1.7 GeV). Structures in SAPHIR / CLAS

data were found, possibly connected with missing resonances like D13(1900).

Need more complete K+ data to reach the conclusion.

K+ (p0)

(pp

N, N*, *

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

Polarization observables (Photon-beam asymmetry etc..) are sensitive to resonance states and model differences because of interference between states.

44

Meson / hyperon exchange in Meson / hyperon exchange in t- /t- / uu-channel-channel

K+

p

K*, K, K1

LEPS energy E = 1.5 - 2.4 GeV is in the transition region,

s-channel t-channel (forward), u-channel (backward) Photon-beam asymmetry at t = 0

and large E: natural parity exchange (K*) = + 1

unnatural parity exchange (K, K1) = － 1

gpKY coupling constant in the u-channel.

Studies of coupled-channel analysis

show non-negligible effect.

K+

p

, Y*

55

Laser-electron photon beamLaser-electron photon beam Linearly polarized photon beam.Linearly polarized photon beam. photon beam asymmetry.photon beam asymmetry. Polarization degree is 95% (55%) at the maximum (minimum) Polarization degree is 95% (55%) at the maximum (minimum)

energy. energy. Use horizontally ( ) and vertically ( ) polarized beam. Use horizontally ( ) and vertically ( ) polarized beam. Energy 1.5 – 2.4 GeV, RMS=15 MeV.Energy 1.5 – 2.4 GeV, RMS=15 MeV. Intensity 1x10Intensity 1x1066 cps. cps.

Forward data Forward data Detect K Detect K+ + ((pp), ID ), ID 00 ( (pp) in missing mass) in missing massBackward data Backward data Detect Detect (p(ppp, ID K, ID K++ in missing mass. in missing mass.

Forward spectrometerForward spectrometer

66

LEPS spectrometer – forward acceptanceLEPS spectrometer – 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

77

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

Detect K+ at forward angles, ID 0 in missing massDetect ppat forward angles, ID K+ in missing mass.

88

Forward KForward K++ photoproduction photoproduction

K+

K+ missing mass spectrum

99

Energy distribution Energy distribution of differential cross sectionsof differential cross sections

W (GeV)

Resonance-like structure

W (GeV)

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

LEPS 　　　　 SAPHIR CLAS

0(1193)(1116)

1010

Angular distribution Angular distribution of differential cross sectionsof differential cross sections

No forward peaking.

0(1193)(1116)

Forward peaking Need Regge poles.

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

LEPS CLAS

1111

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

Some resonances are hidden by other resonances due to their wide widths in cross sections. Polarization observables are a good mean to extract such hidden states.

0(1193)(1116)

1212

Still large variation of models Still large variation of models at backward anglesat backward angles

T. Mart and A. SulaksonoPRC74 (2006) 055203

SAPHIR/LEPS

CLAS/LEPS

SAPHIR/CLAS/LEPS

Used data for fitting in models.

Photon asymmetry

1313

Backward KBackward K++ photoproduction photoproduction

M(pp-)

(1116)

p XK+

p p pp K+, K*, KY*

Detect (pp-) at forward spectrometerIdentify K+ by missing mass technique

1414

Backward KBackward K++ photoproduction photoproductionnucl-ex/ arXiv:0707.4412, K.Hicks, T.Mibe, M.Sumihama, et al.

Curves are theoretical calculation using and * u-channel poles.

1515

Complementary with CLAS dataComplementary with CLAS data

LEPS

CLAS

1616

Photon asymmetry at backward anglesPhoton asymmetry at backward angles

1.5 GeV < E < 2.0 GeV

2.0 GeV < E < 2.4 GeV

p K+

•Experiment with time- projection chamber will start soon. Photon asymmetry at medium region will be measured.

New data at backward angles give constraints to theoretical models.

1717

Backward Backward pp00 photoproduction photoproduction

17

1/10 total statistics

proton missing mass spectrum

M. Sumihama et. al, nucl-ex/0708.1600

1818

Differential cross sectionDifferential cross section coscoscmcm

•Change angular distribution at E~1.8 GeV1.8 GeV, •Backward peakingBackward peaking

Existing data. LEPS data

uu-channel contribution

SAID MAID2005

191919

Energy dependence of slope Energy dependence of slope in differential cross sectionsin differential cross sections

s-7 : quark counting rule

sqrt(s) (GeV)

202020

Photon beam asymmetryPhoton beam asymmetry

SAID LEPS data Existing data. PLB544(2002)113 NPB104(1976)253…

MAID2005

•Strong angular dependence above 1.9 GeV1.9 GeV.•Higher mass resonances need to be included.

Positive sign: Negative sign:

2121

SummarySummary Photon-beam asymmetry and differential cross sections were Photon-beam asymmetry and differential cross sections were

obtained at very forward angles, and backward angles.obtained at very forward angles, and backward angles. Bump structure was seen around W=1960 MeV in the Bump structure was seen around W=1960 MeV in the

KK++mode as well as the CLAS/SAPHIR data. mode as well as the CLAS/SAPHIR data. At forward angles, we observed a forward peaking in KAt forward angles, we observed a forward peaking in K++ but but

no peaking in Kno peaking in K++00. . Photon asymmetry data provide further constraints for models. Photon asymmetry data provide further constraints for models.

Backward peaking is due to u-channel dominance.Backward peaking is due to u-channel dominance. Strong angular dependence of asymmetry reflects the Strong angular dependence of asymmetry reflects the

contribution of higher-mass resonances at Econtribution of higher-mass resonances at E > 1.9 GeV. > 1.9 GeV.

p0 photoproduction

+ photoproduction

2222

LEPS 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