Hyun-Chul Kim Department of Physics Inha University In collaboration with H.Y. Ryu, A. Hosaka, A. Titov EFB 22, Sept. 10, meson photoproduction with hadron rescattering

Motivation OZI rule violation - Gluonic dynamics (Pomeron) - Hidden strangeness Usual vector-meson exchanges are forbidden by the charge conjugation. Hybrid exotic vector mesons (C=+1) are allowed but not much data.

Motivation 텍스트 This bump structure cannot be explained by the pomeron and one meson-exchange picture!

Motivation

How to explain the bump structure around the K Lambda(1520) threshold. How to describe the production mechanism near the threshold in place of the pomeron. In the present talk, we propose possible coupled- channel effects that may explain the phi photoproduction mechanism near the threshold region.

Summary of previous works Titov et al. PRC 60, (1999): Structure of the phi photoproduction Ordinary vector-meson exchange is forbidden. The pomeron governs the energy dependence of the differential cross section, though it is theoretically plausible only at higher energies.

Summary of previous works Mibe et al. PRL, 95, (2005): phi diffractive photoproduction near the threshold Ozaki et al. PRC 80, (2009): K-matrix method (Coupled-channel) Chang et al. PRC 82, (2010): Measurement of the spin-density matrices Kiswandhi et al. PLB 691, 214 (2010): Possible N*(2080) resonance with large strangeness

Effective Lagrangian methods Describe hadron processes in terms of effective degrees of freedom: Quark-gluon dynamics are encoded in the coupling constants and form factors. S.i. Nam, A. Hosaka, HChK, Phys. Rev. D 71, (2005) S.i. Nam, K.S. Choi, A. Hosaka, HChK, D 75, (2005)

Effective Lagrangian methods Invariant amplitude

Production Mechanism A. Titov et al. PRC 60, (1999) Conventional approach Pomeron t-channel hadron exchange Present approach Rescattering amplitudes

Rescattering equation Hadronic part Blankenbecler-Sugar type scattering equation

Rescattering equation Rescattering part in a coupled-channel formalism

Rescattering equation Rescattering part in a coupled-channel formalism In this work, we will consider only the imaginary part for simplicity, to see the reliability of the present method. The full computation is under way.

Rescattering amplitudes Most important term = +

Numerical results Hadrons Hadrons + Pomeron

Differential Cross Sections No Pomeron contribution (E = 2 GeV). Hadronic process can explain the angular distribution.

Differential cross sections Mibe et al. PRL, 95, (2005)

Spin-density matrices

In general, spin-density matrices near the threshold region are well described.

Decay angular distributions C.M. system Gottfried-Jackson system Definition of angles

Decay angular distributions

T. Mibe et al. [LEPS Collaboration], PRL 95, (2005)

23 Summary and Outlook We investigated phi photoproduction, emphasizing the significance of the rescattering contributions, in particular, the K Lambda (1520) channel. The K Lambda (1520) plays a dominant role. However, we have considered here only the imaginary part of the rescattering amplitudes, to see their importance. The real part of the rescattering amplitudes are under investigation, and it seems even more important. The corresponding work will soon appear.

Thank you very much! Though this be madness, yet there is method in it. Hamlet Act 2, Scene 2