Hyun-Chul KimDepartment of Physics

Inha University

In collaboration with H.Y. Ryu, A. Hosaka, A. Titov

EFB 22, Sept. 10, 2013@Kraków

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

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, 035205 (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, 182001 (2005): phi diffractive photoproduction near the threshold

• Ozaki et al. PRC 80, 035201 (2009): K-matrix method (Coupled-channel)

• Chang et al. PRC 82, 015205 (2010): Measurement of the spin-density matrices

• Kiswandhi et al. PLB 691, 214 (2010): Possible N*(2080) resonance with large strangeness

Effective Lagrangian methodsDescribe 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, 114012 (2005) S.i. Nam, K.S. Choi, A. Hosaka, HChK, D 75, 014027 (2005)

Effective Lagrangian methodsInvariant amplitude

Production MechanismA. Titov et al. PRC 60, 035205 (1999)

Conventional approach

Pomeron

t-channel hadron exchange

Present approachRescattering amplitudes

Rescattering equationHadronic part

Blankenbecler-Sugar type scattering equation

Rescattering equationRescattering part in a coupled-channel formalism

Rescattering equationRescattering 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

HadronsHadrons + 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, 182001 (2005)

Spin-density matrices

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

Decay angular distributionsT. Mibe et al. [LEPS

Collaboration], PRL 95, 182001 (2005)

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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