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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 Hosaka1 Hyun-Chul Kim2 1.Research Center for Nuclear Physics (RCNP), Osaka Univ., Japan 2.Nuclear physics & Radiation technology Institute (NuRI), Pusan Univ., Korea　 RCNP & NuRI

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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 ++ 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 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) S.Ricciardi [BABAR], hep-ex/0507027

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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.D71,114012 S.I.N et al.,hep-ph/0505134, submitted to Phys.Lett.B S.I.N et al.,in preparation

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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 *

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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 *? Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

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Photoproduction of Lambda(1520) Photoproduction of (1520) Interactions Parameters gKN* = 11 (Experiment) gK*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 Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

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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

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

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Photoproduction of Lambda(1520) RCNP & NuRI K*-dominance scenario proposed by experiments In the experimental analysis, almost (1520) decayed from its |Sz|=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 |Sz|=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

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CLAS high statistics experiment nK+ invariant M pK0 invariant M Proton Proton (1520) g11 experiment CLAS @JLAB 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

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CLAS high statistics experiment Possible explanation for the null results of the CLAS Taking a look at Feynman diagrams… n-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

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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=+1K*N=3gKN and g=-1K*N=1/3gKN (Quark model) p-wave (=+1) and d-wave (=-1) couplings Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan RCNP & NuRI

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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 < 10 nb and n < 240 nb when 3/2- p< 5 nb and n < 5 nb when 1/2+ Possible explanation for the recent CLAS experiment Experimental data for neutron target is necessary Very2 preliminary CLAS internal report: n < 20 nb N.Baltzell, talk given at CLAS user meeting RCNP & NuRI Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

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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 = gKN and gK* = gKK*  = 1 MeV, g=+1K*N=3gKN and g=-1K*N=1/3gKN (QM)

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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/GeV2]

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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? d/dt [nb/GeV2] Photon beam asymmetry

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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

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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

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

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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?

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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 //K*: -exchange survives ; K*: K-exchange survives Also valid for spin-1/2 baryon photoproduction

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