Generalized form factors and spin structures of the kaon

We investigate the spin structure of the kaon, based on the nonlocal chiral quark model from the instanton vacuum. We first revisit the electromagnetic form factors of the pion and kaon, improving the results for the kaon. We evaluate the generalized tensor form factors of the kaon in order to determine the probability density of transversely polarized quarks inside the kaon. We consider the effects of flavor SU(3) symmetry breaking, so that the probability density of the up and strange quarks are examined in detail. It is found that the strange quark behaves differently inside the kaon in comparison with the up quark.Comment: 9 pages, 7 figures, accepted for publication in Phys. Lett.

Twist-3 pion and kaon distribution amplitudes from the instanton vacuum with flavor SU(3) symmetry breaking

We investigate the twist-3 pion and kaon distribution amplitudes of the pseudoscalar (phi^p_{pi,K}) and pseudotensor (phi^{sigma}_{pi,K}) types, based on the effective chiral action from the instanton vacuum. Effects of flavor SU(3) symmetry breaking are explicitly taken into account. The Gegenbauer moments and the moments of the distribution amplitudes () are also computed. Our results are summarized as follows: a^p_{2,pi} ~ 0.4, a^p_{1,K} ~ 0.02 and a^p_{2,K} ~ 0.14, and a^{sigma}_{2,pi} ~ 0.02 and a^{sigma}_{1,K} ~ a^{sigma}_{2,K} ~ 0; ^p_{\pi} ~ ^p_K ~ 0.37 and ^p_K ~ 0, and ^{sigma}_{pi} ~ ^{sigma}_K ~ 0.20 and ^{sigma}_K ~ 0. We compare our results with those from the QCD sum rules. We also discuss the relevant Wilson coefficients which were analyzed recently in chiral perturbation theory.Comment: 12 pages, 4 figures, accepted for publication in PR

Photon and nucleon induced production of Theta^+

We investigate Theta^+ production via photon and nucleon induced reactions. We observe that the positive parity Theta^+ production provides about ten times larger total cross sections than those of the negative parity one in both photon and nucleon induced reactions due to P-wave enhancement of the K-N-Theta vertex. We also consider the model independent method in the nucleon induced reaction to determine the parity of Theta^+ and show clearly distinguishable signals for the two parities.Comment: 4 pages, 8 figures, Talk given at International Workshop on PENTAQUARK04, Spring-8, Hyogo, Japan, 20-23 Jul 200