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

KˉDˉN\bar{K}\bar{D} N molecular state as a "uudscˉu u d s \bar{c} pentaquark" in a three-body calculation

We predict a new three-body hadronic molecule composed of antikaon $\bar{K}$, anticharm meson $\bar{D}$, and nucleon $N$ with spin/parity $J^{P} = 1/2^{+}$ and isospin $I = 1/2$. This state behaves like an explicit pentaquark state because its minimal quark configuration is $u u d s \bar{c}$ or $u d d s \bar{c}$. Owing to the attraction between every pair of two hadrons, in particular the $\bar{K}\bar{D}$ attraction which dynamically generates $D_{s 0} (2317)^{-}$ and $\bar{K} N$ attraction which dynamically generates $\Lambda (1405)$, the $\bar{K}\bar{D} N$ system is bound, and its eigenenergy is calculated as $3244 - 17 i$ MeV in a nonrelativistic three-body potential model. We discuss properties of this $\bar{K} \bar{D} N$ quasibound state which emerge uniquely in three-body dynamics.Comment: 12 pages, 5 figure

Size measurement of dynamically generated hadronic resonances with finite volume effect

The structures of the hyperon resonance $\Lambda (1405)$ and the scalar mesons $\sigma$, $f_{0}(980)$, and $a_{0}(980)$ are investigated based on the coupled-channels chiral dynamics with finite volume effect. The finite volume effect is utilized to extract the coupling constant, compositeness, and mean squared distance between two constituents of a Feshbach resonance state as well as a stable bound state. In this framework, the real-valued size of the resonance can be defined from the downward shift of the resonance pole according to the decreasing finite box size $L$ on a given closed channel. As a result, we observe that, when putting the $\bar{K}N$ and $K\bar{K}$ channels into a finite box while other channels being unchanged, the poles of the higher $\Lambda (1405)$ and $f_{0}(980)$ move to lower energies while other poles do not show downward mass shift, which implies large $\bar{K}N$ and $K\bar{K}$ components inside higher $\Lambda (1405)$ and $f_{0}(980)$, respectively. Extracting structures of $\Lambda (1405)$ and $f_{0}(980)$ in our method, we find that the compositeness of $\bar{K}N$ ($K\bar{K}$) inside $\Lambda (1405)$ [$f_{0}(980)$] is 0.82-1.03 (0.73-0.97) and the mean distance between two constituents is evaluated as 1.7-1.9 fm (2.6-3.0 fm).Comment: 5 pages, 1 figure, talk given at XV International Conference on Hadron Spectroscopy (Hadron 2013), Nara, Japan, 4-8 November 201

Compositeness of baryonic resonances: Applications to the Delta(1232), N(1535), and N(1650) resonances

We present a formulation of the compositeness for baryonic resonances in order to discuss the meson-baryon molecular structure inside the resonances. For this purpose, we derive a relation between the residue of the scattering amplitude at the resonance pole position and the two-body wave function of the resonance in a sophisticated way, and we define the compositeness as the norm of the two-body wave functions. As applications, we investigate the compositeness of the $\Delta (1232)$, $N (1535)$, and $N (1650)$ resonances from precise $\pi N$ scattering amplitudes in a unitarized chiral framework with the interaction up to the next-to-leading order in chiral perturbation theory. The $\pi N$ compositeness for the $\Delta (1232)$ resonance is evaluated in the $\pi N$ single-channel scattering, and we find that the $\pi N$ component inside $\Delta (1232)$ in the present framework is nonnegligible, which supports the previous work. On the other hand, the compositeness for the $N (1535)$ and $N (1650)$ resonances is evaluated in a coupled-channels approach, resulting that the $\pi N$, $\eta N$, $K \Lambda$ and $K \Sigma$ components are negligible for these resonances.Comment: 23 pages, 7 eps figures, version accepted for publication in PRC, discussions improve

Two-body wave functions and compositeness from scattering amplitudes: II. Application to the physical N∗N ^{\ast} and Δ∗\Delta ^{\ast} resonances

The meson-baryon molecular components for the $N^{\ast}$ and $\Delta ^{\ast}$ resonances are investigated in terms of the compositeness, which is defined as the norm of the two-body wave function from the meson-baryon scattering amplitudes. The scattering amplitudes are constructed in a $\pi N$-$\eta N$-$\sigma N$-$\rho N$-$\pi \Delta$ coupled-channels problem in a meson exchange model together with several bare $N^{\ast}$ and $\Delta ^{\ast}$ states, and parameters are fitted so as to reproduce the on-shell $\pi N$ partial wave amplitudes up to the center-of-mass energy 1.9 GeV with the orbital angular momentum $L \le 2$. As a result, the Roper resonance $N (1440)$ is found to be dominated by the $\pi N$ and $\sigma N$ molecular components while the bare-state contribution is small. The squared wave functions in coordinate space imply that both in the $\pi N$ and $\sigma N$ channels the separation between the meson and baryon is about more than 1 fm for the $N (1440)$ resonance. On the other hand, dominant meson-baryon molecular components are not observed in any other $N^{\ast}$ and $\Delta ^{\ast}$ resonances in the present model, although they have some fractions of the meson-baryon clouds.Comment: 20 pages, 5 figure

Theoretical analysis on the K−3He→ΛpnK^{-} {}^{3} \text{He} \to \Lambda p n reaction for the KˉNN\bar{K} N N bound-state search in the J-PARC E15 experiment

We theoretically analyze the $K^{-} {}^{3} \text{He} \to \Lambda p n$ reaction for the $\bar{K} N N$ bound-state search in the J-PARC E15 experiment. We find that, by detecting a fast and forward neutron in the final state, an almost on-shell $\bar{K}$ is guaranteed, which is essential to make a bound state with two nucleons from ${}^{3} \text{He}$. Then, this almost on-shell $\bar{K}$ can bring a signal of the $\bar{K} N N$ bound state in the $\Lambda p$ invariant-mass spectrum, although it inevitably brings a kinematic peak above the $\bar{K} N N$ threshold as well. As a consequence, we predict two peaks across the $\bar{K} N N$ threshold in the spectrum: the lower peak coming from the $\bar{K} N N$ bound state, and the higher one originating from the kinematics.Comment: 4 pages, 4 EPS figures, talk given at XVII International Conference on Hadron Spectroscopy and Structure (Hadron2017), Salamanca, Spain, 25-29 September, 201

Mesonic and non-mesonic branching ratios of K^- absorption in the nuclear medium

The branching ratios of K^- absorption at rest in nuclear matter are evaluated from the K^- self-energy by using the chiral unitary approach for the s-wave \bar{K} N amplitude. We find that both the mesonic and non-mesonic absorption potentials are dominated by the \Lambda(1405) contributions. We also observe that the mesonic absorption ratio [\pi ^{-} \Sigma ^{+}] / [\pi ^{+} \Sigma ^{-}] increases as a function of nuclear density due to the interference between \Lambda(1405) and the I=1 non-resonant background, which is consistent with experimental results. The fraction of the non-mesonic absorption is evaluated to be about 30 % at the saturation density. The branching ratios of the K^- absorption at rest into deuteron and 4He are also calculated.Comment: 4 pages, 3 figures, talk given at XI International Conference on Hypernuclear and Strange Particle Physics (HYP2012), Barcelona, Spain, 1-5 October 201

Electromagnetic Mean Squared Radii of Lambda(1405) in Meson-baryon Dynamics with Chiral Symmetry

Electromagnetic mean squared radii of Lambda(1405) are evaluated in chiral unitary approach. In this approach we regard Lambda(1405) as dynamically generated resonances in the octet meson and octet baryon scattering, and also as KbarN bound state. Especially for the Lambda(1405) as KbarN bound state we obtain negative electric mean squared radius. With the small binding energy of Lambda(1405) in the chiral unitary approach, our results imply that Lambda(1405) has structure that K^- is widely spread around p.Comment: 4 pages, 2 figures, use ptptex.cls. Talk given at YITP International Symposium: Fundamental Problems in Hot and/or Dense QCD, Kyoto, Japan, 3-6 Mar 200

What makes the peak structure of the Λp\Lambda p invariant-mass spectrum in the K−3He→ΛpnK^{-} {}^{3} {\rm He} \to \Lambda p n reaction?

Recently a peak structure was observed near the $K^{-} p p$ threshold in the in-flight ${}^{3} {\rm He} (K^{-} , \, \Lambda p) n$ reaction of the E15 experiment at J-PARC, which could be a signal of a $\bar{K} N N$ bound state. In order to investigate what is the origin of this peak, we calculate the cross section of this reaction, in particular based on the scenario that the $\bar{K} N N$ bound state is indeed generated and decays into $\Lambda p$. We find that the numerical result of the $\Lambda p$ invariant-mass spectrum in the $\bar{K} N N$ bound scenario is consistent with the J-PARC E15 data.Comment: 6 pages, 6 EPS figures, talk given at the 2nd Jagiellonian Symposium on Fundamental and Applied Subatomic Physics, Krakow, Poland, 4-9 June, 201

Possible η′d\eta' d bound state and its ss-channel formation in the γd→ηd\gamma d \to \eta d reaction

We theoretically investigate a possibility of an $\eta ^{\prime} d$ bound state and its formation in the $\gamma d \to \eta d$ reaction. First, in the fixed center approximation to the Faddeev equations we obtain an $\eta ^{\prime} d$ bound state with a binding energy of 25 MeV and width of 19 MeV, where we take the $\eta ^{\prime} N$ interaction with a coupling to the $\eta N$ channel from the linear $\sigma$ model. Then, in order to investigate the feasibility from an experimental point of view, we calculate the cross section of the $\gamma d \to \eta d$ reaction at the photon energy in the laboratory frame around 1.2 GeV. As a result, we find a clear peak structure with the strength $\sim$ 0.2 nb/sr, corresponding to a signal of the $\eta ^{\prime} d$ bound state in case of backward $\eta$ emission. This structure will be prominent because a background contribution coming from single-step $\eta$ emission off a bound nucleon is highly suppressed. In addition, the signal can be seen even in case of forward $\eta$ emission as a bump or dip, depending on the relative phase between the bound-state formation and the single-step background.Comment: 9 pages, 13 eps figures, version accepted for publication in PRC, description of the discussion part is improve