arXiv subjects

A. Hosaka

Publications and source records attributed to A. Hosaka.

102 records · Page 6Linked to original sources

arXiv2000

Chiral Unitary Approach To The NNpi, NNeta Couplings For The N*(1535) Resonance

Using a chiral unitary model in which the negative parity nucleon resonance $N^\ast \equiv N^\ast(1535)$ is generated dynamically by means of the Bethe Salpeter equation with coupled meson baryon channels in the $S = 0$ sector, we have obtained the $π^0 N^\ast N^\ast$ and $ηN^\ast N^\ast$ couplings. The $π^0 N^\ast N^\ast$ coupling has smaller strength and the same sign as the $π^0 N N$ coupling. This rules out the mirror assignment of chiral symmetry where the ground state nucleon $N$ and the negative parity resonance $N^\ast$ are envisaged as chiral partners in the baryon sector.

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arXiv1999

SU(3) Chiral approach to meson and baryon dynamics

We report on recent progress on the chiral unitary approach, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV and meson baryon interaction up to the first baryonic resonances. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, concretely the K^- p\toΛ(1405)γreaction and the N^\ast (1535)N^\ast(1535)πand ηcouplings.

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arXiv1998

Phenomenological Study of Excited Baryons

We study baryon excited states for quark confinement and chiral symmetry breaking. In the first part we discuss spatially deformed baryon excitations. As signals of deformation, we study masses and electromagnetic transitions. Such a study of spatial structure is expected to provide information on quark binding mechanism and hence quark confinement. In the second part, we consider the chiral symmetry for baryons and study positive and negative parity baryons. We show that there are two distinctive representations of chiral symmetry for baryons. We investigate their phenomenological consequences in terms of linear sigma models.

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arXiv1998

Chiral Symmetry for Positive and Negative Parity Nucleons

Chiral properties of positive and negative parity nucleons, N and N*$, are studied from the viewpoint of chiral symmetry. Two possible ways to assign chiral transformations to the negative parity nucleon are considered. Using linear sigma models based on the two chiral realizations, theoretical as well as phenomenological consequences of the two different assignments are investigated. We find that the nucleon mass in the chiral restored phase is the key quantity to determine the meson-nucleon couplings and the axial charges of nucleons. We also discuss the role of chiral symmetry breaking in the mass splitting of N and N* in the two sigma models.

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arXiv1998

Suppression of Pi NN* Coupling and Chiral Symmetry

Meson-baryon couplings between positive and negative parity nucleons are investigated using two point correlation functions in the soft meson and the chiral limit. We find that the pi NN* coupling vanishes due to chiral symmetry, while the eta NN* coupling remains finite. We perform an analysis based on the algebraic method for SU(2) chiral symmetry, and find that nucleon axial charges play an essential role for vanishing coupling constants. For an illustration, we construct sigma models with N and N*, where we discuss their properties from the view point of the chiral symmetry. We also discuss N and N* in the viewpoint of chiral partner.

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arXiv1997

Baryon Spectra in Deformed Oscillator Quark Model

We study theoretically the baryon spectra in terms of a deformed oscillator quark (DOQ) model. This model is motivated by confinement of quarks and chiral symmetry breaking, which are the most important non-perturbative phenomena of QCD. The minimization of the DOQ hamiltonian with respect to the deformation for each principal quantum number results in deformations for the intrinsic states of excited baryonic states. We find that the resulting baryon spectra agree very well with the existing experimental data. The spatial deformation of the baryonic excited states carry useful information on the quark confinement and provide a clue to understand the confining mechanism.

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arXiv1997

Decays of 1/2^- Baryons in Chiral Effective Theory

We construct an $SU(3)_L \times SU(3)_R$ symmetric chiral effective model which includes parity pair baryon fields. It is assumed that the positive and negative parity baryons in the parity pair have opposite chiral transformation properties each other. Using this model, strong decays of the negative parity baryons are studied up to the order of one-loop corrections. The results agree qualitatively with experiment in the $π$ and $K$ channels. We examine how the model parameters are determined from the decay widths and study their physical meanings. Possibilities to build other models and relations to the correlation function analysis are discussed.

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arXiv1997

Suppression of PiNN* Coupling and Chiral Symmetry

Meson-baryon couplings between positive and negative parity baryons are investigated using two point correlation functions in the soft meson limit. We find that the pi NN^* coupling vanishes due to chiral symmetry, while the eta NN^* coupling remains finite. We perform an analysis based on the algebraic method for SU(2) and SU(3) chiral symmetry, and find that baryon axial charges play an essential role for vanishing coupling constants.

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arXiv1997

Suppression of PiNN(1535) Coupling in the QCD Sum Rule

The πNN^* and ηNN^* coupling constants are studied based on the two point functions between the vacuum and a one meson state in the soft meson limit. In terms of a suitably constructed interpolating field for the nucleon and resonances, we have found that the πNN^* couplings vanish, while ηNN^* couplings remain finite. This result explains a relatively suppressed coupling of πNN(1535) as compared with others. We compare the present result with predictions of low energy effective models.

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arXiv1997

Negative Parity Baryons in the QCD Sum Rule

Masses and couplings of the negative parity excited baryons are studied in the QCD sum rule. Separation of the negative-parity spectrum is proposed and is applied to the flavor octet and singlet baryons. We find that the quark condensate is responsible for the mass splitting of the ground and the negative-parity excited states. This is expected from the chiral symmetry and supports the idea that the negative-parity baryon forms a parity doublet with the ground state. The meson-baryon coupling constants are also computed for the excited states in the QCD sum rule. It is found that the πNN^* coupling vanishes in the chiral limit.

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arXiv1997

Suppression of PiNN(1535) Coupling in the QCD Sum Rule

The πNN^* and ηNN^* coupling constants are studied in the QCD sum rule ($N^* \equiv N(1535)). We investigate the two point functions between the vacuum and a one meson state in the soft meson limit. The operator product expansion is explicitly performed up to terms of dimension eight. We find that \gpNR vanishes to this order, while \geNR has a finite contribution. The vanishing of \gpNR is a rigorous consequence in the chiral limit. The results of the QCD sum rule are compared with those of low energy effective models.

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arXiv1996

Nuclear G-Matrix Elements from Nonlocal Potentials

We study effects of nonlocality in the nuclear force on the G-matrix elements for finite nuclei. Nuclear G-matrix elements for $\O16$ are calculated in the harmonic oscillator basis from a nonlocal potential which models quark exchange effects between two nucleons. We employ a simple form of potential that gives the same phase shifts as a realistic local nucleon potential. The G-matrix elements calculated from the nonlocal potential show moderate increase in repulsion from those derived from the local potential.

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