arXiv subjects

Tetsuo Hyodo

Publications and source records attributed to Tetsuo Hyodo.

140 records · Page 8Linked to original sources

arXiv2008

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.

nucl-th↗

arXiv2008

Structure of the Lambda(1405) baryon resonance from its large Nc behavior

We study the behavior with the number of colors (Nc) of the two poles associated to the Lambda(1405) resonance obtained dynamically within the chiral unitary approach. The leading order chiral meson-baryon interaction manifests a nontrivial Nc dependence for SU(3) baryons, which gives a finite attractive interaction in some channels in the large Nc limit. As a consequence, the SU(3) singlet (Kbar N) component of the Lambda(1405) survives in the large Nc limit as a bound state, while the other components dissolve into the continuum. The Nc dependence of the decay widths shows different behavior from the general counting rule for a qqq state, indicating the dynamical origin of the two poles for the Lambda(1405) resonance.

hep-ph↗

arXiv2008

The structure of N(1535) in the aspect of chiral symmetry

The structure of N(1535) is discussed in dynamical and symmetry aspects based on chiral symmetry. We find that the N(1535) in chiral unitary model has implicitly some components other than meson-baryon one. We also discuss the N(1535) in the chiral doublet picture.

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arXiv2008

Effective Kbar N interaction based on chiral SU(3) dynamics

The effective Kbar N interaction based on chiral SU(3) coupled-channel dynamics is derived and its extrapolation below the Kbar N threshold is studied in detail. Starting from the coupled-channel scattering equations, we eliminate the channels other than Kbar N and obtain an effective interaction in the single Kbar N channel. An equivalent local potential in coordinate space is constructed such as to reproduce the full scattering amplitude of the chiral SU(3) coupled-channel framework. We discuss several realistic chiral SU(3)-based models in comparison to reach conclusions about the uncertainties involved. It turns out that, in the region relevant to the discussion of deeply bound Kbar-nuclear few-body systems, the resulting energy-dependent, equivalent local potential is substantially less attractive than the one suggested in previous purely phenomenological treatments.

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arXiv2008

Exotic hadrons and SU(3) chiral dynamics

We explore a possibility to generate exotic hadrons dynamically in the scattering of hadrons. The s-wave scattering amplitude of an arbitrary hadron with the Nambu-Goldstone boson is constructed so as to satisfy the unitarity condition and the chiral low energy theorem. We find that the chiral interaction for the exotic channels is in most cases repulsive, and that the strength of the possible attractive interaction is uniquely determined. We show that the attractive interaction in exotic channels is not strong enough to generate a bound state, while the interaction in nonexotic channel generate bound states which are considered to be the origin of some resonances observed in nature.

hep-ph↗

arXiv2008

Lambda(1405) in chiral SU(3) dynamics

We discuss several aspects of the Lambda(1405) resonance in relation to the recent theoretical developments in chiral dynamics. We derive an effective single-channel KbarK N interaction based on chiral SU(3) coupled-channel approach, emphasizing the important role of the pi Sigma channel and the structure of the Lambda(1405) in Kbar N phenomenology. In order to clarify the structure of the resonance, we study the behavior with the number of colors (Nc) of the poles associated with the Lambda(1405), and argue the physical meaning of the renormalization procedure.

hep-ph↗

arXiv2008

$K^-pp$ system with chiral SU(3) effective interaction

The $K^-pp$ system is investigated using a variational approach with realistic two-body interactions: the Argonne v18 $NN$ potential and an energy dependent $\bar{K}N$ effective interaction derived from chiral SU(3) coupled-channel dynamics. Uncertainties in subthreshold extrapolations of the $\bar{K}N$ interaction are considered. A weakly bound $K^-pp$ state is found, with a binding energy $B = (19\pm 3)$ MeV substantially smaller than suggested in previous calculations. The decay width $Γ(K^-pp\to πΣN)$ is estimated to range between about 40 and 70 MeV.

nucl-th↗

arXiv2007

Study of exotic hadrons in s-wave chiral dynamics

We study the exotic hadrons in s-wave scattering of the Nambu-Goldstone boson with a target hadron based on chiral dynamics. Utilizing the low energy theorem of chiral symmetry, we show that the s-wave interaction is not strong enough to generate bound states in exotic channels in flavor SU(3) symmetric limit, although the interaction is responsible for generating some nonexotic hadron resonances dynamically. We discuss the renormalization condition adopted in this analysis.

hep-ph↗

arXiv2007

Study of exotic hadrons in S-wave scatterings induced by chiral interaction in the flavor symmetric limit

We study s-wave bound states of a hadron and a light pseudoscalar meson induced by the Weinberg-Tomozawa (WT) interaction in the flavor SU(3) symmetric limit. The WT interaction is a driving force to generate quasibound states dynamically in the chiral unitary approaches. The strength and sign of the WT interaction are determined only by the group theoretical structure of the target hadrons, and we present a general expression of the strengths for the flavor SU(3) case. We show that, for the channels which are more exotic than the target, the interaction is repulsive in most cases, and the strength of the attractive interaction is universal for any possible target states. We demonstrate that the attractive coupling is not strong enough to generate an exotic state from the physically known masses of target hadrons. In addition, we also find a nontrivial Nc dependence of the coupling strengths. We show that the channels which are attractive at Nc=3 changes into repulsive ones for large Nc, and, therefore, no attractive interaction exists in exotic channels in the large-Nc limit.

hep-ph↗

arXiv2006

Chiral dynamics and s-wave exotic hadrons

Based on chiral dynamics, existence of exotic hadrons is discussed in the SU(3) symmetric limit. The low energy s-wave interaction of the Nambu-Goldstone boson with a hadron is known to be determined model-independently, which has been used to generate some hadron resonances in nonexotic channels. We show that this interaction in any exotic channels is not strong enough to generate a bound state.

hep-ph↗

arXiv2006

Exotic hadrons in s-wave chiral dynamics

We study s-wave scattering of a hadron and a Nambu-Goldstone boson induced by the model-independent low energy interaction in the flavor SU(3) symmetric limit. Establishing the general structure of the low energy interaction based on group theoretical arguments, we find that the interaction in the exotic channels are in most cases repulsive, and that for possible attractive channels the interaction strengths are weak and uniquely given independent of channel. Solving the scattering problem with this interaction, we show that the attraction in the exotic channels is not strong enough to generate a bound state from the physically known target hadrons. We also find that there are no attractive interaction in the exotic channels in large Nc limit.

hep-ph↗

arXiv2006

Phenomenological study for the Theta+ and two-meson coupling

We examine several assignments of spin and parity for the pentaquark Theta+ state (J^P=1/2^{+,-}, 3/2^{+,-}) in connection with phenomenology of known baryon resonances, using a general framework based on the flavor symmetry. Assuming that the Theta+ belongs to an antidecuplet representation which mixes with an octet, we calculate the mass spectra of the flavor partners of the Theta+ based on the SU(3) symmetry. The decay widths of the Theta+ and nucleon partners are analyzed for the consistency check of the mixing angle obtained from the masses. It is found that a suitable choice of the mixing angle successfully reproduces the observed masses of exotics, when their spin and parity are assigned to be J^P=3/2^-, together with other nonexotic resonances of J^P=3/2^-. The decay widths of Theta -> KN, N(1520) -> pi N, and N(1700) -> pi N are also reproduced simultaneously. We then evaluate two-meson couplings of Theta+, using experimental information of nucleon partners decaying into pi pi N channels, in which the two pions are in scalar- and vector-type correlations. We examine two assignments of spin and parity J^P=1/2^+ and 3/2^-, for which the experimental spectra of known resonances with exotic baryons are properly reproduced by an octet-antidecuplet representation mixing scheme. Using the obtained coupling constants, total cross sections of the reactions pi- p -> K- Theta+ and K+ p -> pi+ Theta+ are calculated. Substantial interference of two terms may occur in the reaction processes for the J^P=1/2^+ case, whereas the interference effect is rather small for the 3/2^- case.

hep-ph↗

arXiv2005

Phenomenological study of two-meson couplings of Theta+

We evaluate two-meson couplings of Theta+, using experimental information of nucleon resonances decaying into pi pi N channels, in which the two pions are in scalar- and vector-type correlations. We examine two assignments of spin and parity of J^P=1/2^+ and 3/2^-, for which the experimental spectra of known resonances with exotic baryons are properly reproduced by an octet-antidecuplet representation mixing scheme. With the obtained coupling constants, total cross sections of the reactions pi- p -> K- Theta+ and K+ p -> pi+ Theta+ are calculated. Substantial interference of two terms may occur in the reaction processes for the J^P=1/2^+ case, whereas the interference effect is rather small for the 3/2^- case.

hep-ph↗

arXiv2005

Phenomenology of spin 3/2 baryons with pentaquarks

We examine several assignments of spin and parity for the pentaquark Theta+ state (J^P=1/2^{+,-}, 3/2^{+,-}) in connection with known baryon resonances. Assuming that the Theta+ belongs to an antidecuplet representation which mixes with an octet, we calculate the mass spectra of the flavor partners of the Theta+ based on the SU(3) symmetry. The decay widths of the Theta+ and nucleon partners are analyzed for the consistency check of the mixing angle obtained from the masses. It is found that a suitable choice of the mixing angle successfully reproduces the observed masses of Theta(1540) and Xi_{3/2}(1860), when their spin and parity are assigned to be J^P=3/2^-, together with other J^P=3/2^- resonances. The decay widths of Theta -> KN, N(1520) -> pi N, and N(1700) -> pi N are also reproduced simultaneously.

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