Ξ(1690)\Xi (1690) as a KˉΣ\bar{K} \Sigma molecular state

We show that a $\Xi ^{\ast}$ pole can be dynamically generated near the $\bar{K} \Sigma$ threshold as an $s$-wave $\bar{K} \Sigma$ molecular state in a coupled-channels unitary approach with the leading-order chiral interaction. This $\Xi ^{\ast}$ state can be identified with the $\Xi (1690)$ resonance with $J^{P} = 1/2^{-}$. We find that the experimental $\bar{K}^{0} \Lambda$ and $K^{-} \Sigma ^{+}$ mass spectra are qualitatively reproduced with the $\Xi ^{\ast}$ state. Moreover we theoretically investigate properties of the dynamically generated $\Xi ^{\ast}$ state.Comment: 10 pages, 3 eps files, version accepted for publication in PTE

Constraint on K Kbar compositeness of the a0(980) and f0(980) resonances from their mixing intensity

Structure of the $a_{0}(980)$ and $f_{0}(980)$ resonances is investigated with the $a_{0}(980)$-$f_{0}(980)$ mixing intensity from the viewpoint of compositeness, which corresponds to the amount of two-body states composing resonances as well as bound states. For this purpose we first formulate the $a_{0}(980)$-$f_{0}(980)$ mixing intensity as the ratio of two partial decay widths of a parent particle, in the same manner as the recent analysis in BES experiments. Calculating the $a_{0}(980)$-$f_{0}(980)$ mixing intensity with the existing Flatte parameters from experiments, we find that many combinations of the $a_{0}(980)$ and $f_{0}(980)$ Flatte parameters can reproduce the experimental value of the $a_{0}(980)$-$f_{0}(980)$ mixing intensity by BES. Next, from the same Flatte parameters we also calculate the $K \bar{K}$ compositeness for $a_{0}(980)$ and $f_{0}(980)$. Although the compositeness with the correct normalization becomes complex in general for resonance states, we find that the Flatte parameters for $f_{0}(980)$ imply large absolute value of the $K \bar{K}$ compositeness and the parameters for $a_{0}(980)$ lead to small but nonnegligible absolute value of the $K \bar{K}$ compositeness. Then, connecting the mixing intensity and the $K \bar{K}$ compositeness via the $a_{0}(980)$- and $f_{0}(980)$-$K \bar{K}$ coupling constants, we establish a relation between them. As a result, a small mixing intensity indicates a small value of the product of the $K \bar{K}$ compositeness for the $a_{0}(980)$ and $f_{0}(980)$ resonances. Moreover, the experimental value of the $a_{0}(980)$-$f_{0}(980)$ mixing intensity implies that the $a_{0}(980)$ and $f_{0}(980)$ resonances cannot be simultaneously $K \bar{K}$ molecular states.Comment: 15 pages, 6 figures, version accepted for publication in PR

Electric Mean Squared Radii of Lambda(1405) in Chiral Dynamics

The electric mean squared radii _E of Lambda(1405) are calculated in the chiral unitary model. We describe the Lambda(1405) as a dynamically generated resonance fully in the octet meson and octet baryon scattering. We also consider ``Lambda(1405)'' as a bound state of KbarN. For the later ``Lambda(1405),'' we obtain negative and larger absolute value of electric mean squared radius than that of ordinary baryons, which implies that Lambda(1405) have structure of widely spread K^- around p.Comment: 4 pages, 1 figure, use ws-mpla.cls. Talk given at Workshop on Chiral Symmetry in Hadron and Nuclear Physics: Chiral07, Osaka, Japan, 13-16 Nov 200