Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan  + photoproduction with vector K* (including other recent results) Seung-il Nam *1,2 Atsushi Hosaka 1 Hyun-Chul Kim 2 1.Research Center for Nuclear Physics (RCNP), Osaka Univ., Japan 2.Nuclear physics & Radiation technology Institute (NuRI), Pusan Univ., Korea RCNP & NuRI

Recent status of Theta Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI Recent experiments for pentaquark baryons  New evidence for  + by LEPS at Spring-8   (1520) (=  *) photoproduction revisited experimentally by LEPS ð  ++ announced by STAR  No clear evidence for  + CLAS at JLAB  Negative results from BABAR etc Controversial experimental situations  Considering photoproduction of  +, (LEPS and CLAS) Positive results out of neutron target vs. Negative results out of proton target Positive results out of neutron target vs. Negative results out of proton target  Suppression of total cross section for proton?  What is the suppression mechanism? Huang, talk given at Beijing (2005) R.De Vita, talk given at APS (2005) talk given at Nara (2005) T.Nakano, talk given at Beijing (2005) S.Ricciardi [BABAR], hep-ex/

Recent status of Theta Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI Theoretical interests in this talk   * photoproduction concerning  + : new analysis  Possible interpretation for CLAS result: Isospin asymmetry   + photoproduction with K* : reaction process analysis Theoretical framework  Effective Lagrangian approach  The Born approximation at tree level  Phenomenological form factor maintaining the Ward-Takahashi identity  Parameters estimated by phenomenological consideration and model calculation  Experimental data used for fixing cutoff  S.I.N et al.,Phys.Rev.D71, S.I.N et al.,hep-ph/ , submitted to Phys.Lett.B S.I.N et al.,in preparation

Photoproduction of Lambda* Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI Strong correlation between  and  (1520)  New evidence of  + by LEPS at Spring-8 using deuteron target  Simultaneous productions of  + and  * K-K-K-K- D ++++ p **** D ++++  << 1

 (1520) invariant mass K - p missing mass for  Photoproduction of Lambda*  + photoproduction from deuteron target by LEPS  Only for  * resonant region, peak for  appears  Motivation: Is it possible for extracting information for  via  *? **** K-K-K-K- D ++++ p Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

Photoproduction of Lambda(1520) Photoproduction of  (1520)  Interactions  Parameters g KN  * = 11 (Experiment) g K*N  * =0,  11 (Quark model)  Rarita-Schwinger vector-spinor field W.Rarita et al.,Phys.Rev.60,61  No PS coupling scheme due to     = 0 and     = 0     = 0 and     = 0 Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

Photoproduction of Lambda*  p   +  * : Proton target  Qulitaively well reproduced experimental data; Cutoff  =750 MeV  Dominant contact term (Kroll-Ruderman) D.P.Barber [Daresbury],Z.Phys.C7,17 Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

Photoproduction of Lambda*  n   0  * : Neutron target (No data for cross section)  ~30 times smaller  n  than  p  due to absence of the contact term  Large asymmetry actually shown in the recent LEPS experiment No K* T.Nakano, talk given at Beijing (2005) talk given at Nara (2005) No K* Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

3/2 3/2 3/2 1/2 1/2 1/2 Contact K(spin-0)-exchange K*(spin-1)-exchange Photoproduction of Lambda(1520) RCNP & NuRI K* -dominance scenario proposed by experiments  In the experimental analysis, almost  (1520) decayed from its |S z |=3/2 state  From this fact, K* -exchange was believed as dominant contribution ( t -channel)  Theoretical proof: Is this conclusion is correct?  Natural consequences for K and K*  Large |S z |=3/2 contribution from the contact term not from K* D.P.Barber [Daresbury],Z.Phys.C7,17 Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

CLAS high statistics experiment nK + invariant M pK 0 invariant M ProtonProton  (1520) g11 experiment  Proton target  No obvious peak for   Estimation:  p  /  p  < 0.2%  Corresponding to  p  < 2 nb The cross section from the proton suppressed?  Positive evidence from the neutron target (LEPS)  Asymmetry between neutron and proton targets?  Hinted by  (1520) photoproduction  If  (1520) and  + behave similarly in reaction processes: Spin-3/2  + R.De Vita, talk given at APS (2005) Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

CLAS high statistics experiment Possible explanation for the null results of the CLAS  Taking a look at Feynman diagrams… 0000n  (1520) e=0  bar 0  p  + (1540) e=0 ++++ p  (1520) e=1 ----n  + (1540) e=1 ðn-p asymmetry for spin-3/2  photoproduction  Suppression to the proton target! Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

Photoproduction of Theta(3/2) Photoproduction of  + (3/2):  Kbar  + (3/2)  Analogous calculations to  * photoproduction: Cutoff  =750 MeV  Clear n-p asymmetries for two parities    = 1 MeV, g  =+1 K*N  =  3g KN  and g  =-1 K*N  =1/  3g KN  (Quark model)  p -wave (  =+1) and d -wave (  =-1) couplings  =+1  =-1 NeutronProtonNeutronProton Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

Photoproduction of Theta(3/2) Photoproduction of  + (3/2):  Kbar  + (3/2)  Clear n-p asymmetry  Our estimation with   =1 MeV  p  < 2 nb and  n  < 30 nb when 3/2 +  p  < 2 nb and  n  < 30 nb when 3/2 +  p  < 10 nb and  n  < 240 nb when 3/2 -  p  < 10 nb and  n  < 240 nb when 3/2 -  p  < 5 nb and  n  < 5 nb when 1/2 +  p  < 5 nb and  n  < 5 nb when 1/2 +  Possible explanation for the recent CLAS experiment  Experimental data for neutron target is necessary  Very 2 preliminary CLAS internal report:  n  < 20 nb Strong suppression for the proton target } N.Baltzell, talk given at CLAS user meeting RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

Photoproduction of Theta(3/2) RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Photoproduction of  + (3/2):  K*bar  + (3/2)  Reaction  N     + including  N   * bar  + subprocess (planned at CLAS)  Three vector meson coupling  *  * necessary for gauge invariance  Including  (800,0 + ) with g  N  = g KN  and g  K* = g  KK*    = 1 MeV, g  =+1 K*N  =  3g KN  and g  =-1 K*N  =1/  3g KN  (QM)

Photoproduction of Theta(3/2) RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Photoproduction of  K*bar  + (3/2): Positive parity  No obvious n-p asymmetry  K -exchange ~ contact term  Strong forward scattering Photon beam asymmetry d  /dt [nb/GeV 2 ]

Photoproduction of Theta(3/2) RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Photoproduction of  K*bar  + (3/2): Negative parity  No obvious n-p asymmetry  Strong forward scattering  Rather different PBA from  =+1 Determination of the parity? Determination of the parity? d  /dt [nb/GeV 2 ] Photon beam asymmetry

Photoproduction of Theta(1/2) RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Photoproduction of  K*bar  + (1/2): Positive parity  No obvious n-p asymmetry  Strong forward scattering  Rather different PBA’s Photon beam asymmetry 3/2 + Photon beam asymmetry 3/2 -

Photoproduction of Theta(3/2) RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Polarizatios in  K*bar  +  Two polarizations: photon and K*  Looking at amplitudes….  When photon perpendicular to scattering plane: K* -contribution disappears x z y  K*(k 2 )  KKKK y-z plane //  K  N   ·p K*

Photoproduction of Theta(3/2) RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Polarizatios in  K*bar  +  :  -exchange survives    //  K* :  -exchange survives  : K -exchange survives     K* : K -exchange survives Parallel:   //  K* Perpendicular:    K* Due to the amplitude structures }

Summary and conclusion RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan  (1520) photoproduction  Strong correlation between  + and  * shown by recent LEPS exp.  Qualitatively well reproduced data for proton target  Predictions for neutron target: much smaller cross sections  Dominant contact term contribution: n-p asymmetry or Isospin asymmetry  Experiments showed the asymmetry actually Recent CLAS exp.  No obvious peak for  + : basically proton-photon scattering  New LEPS evidence from neutron target: What happened?  Strong suppression expected for proton target  What is the suppression mechanism?  Suggestion: if  + spin-3/2, the suppression occurs?

Summary and conclusion RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan  + (3/2) photoproduction  Analougous calculations to those of  (1520)  Obvious n-p asymmetry shown: Suppression to the proton target   p  < 2 nb and  n  < 30 nb when 3/2 + ;  p  < 10 nb and  n  < 240 nb when 3/2 -  Less dependent on K* -contribution than spin-1/2  +  + (3/2) photoproduction with vector K*bar  scalar kaon  (800)-exchange possible  Two polarizations possible: incident photon and outgoing K*  Selection rule for interchanging kaon after fixing photon polarization  :  -exchange survives ; : K -exchange survives    //  K* :  -exchange survives ;    K* : K -exchange survives  Also valid for spin-1/2 baryon photoproduction

RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Thank you very much