Searcharxiv⌕ Search

arXiv subjects

T. Hyodo

Publications and source records attributed to T. Hyodo.

33 records · Page 2Linked to original sources
arXiv2005

Two-meson cloud contribution to the baryon antidecuplet self-energy

We study the self-energy of the SU(3) antidecuplet coming from two-meson virtual clouds. Assuming that the exotic Theta+ belongs to an antidecuplet representation with N(1710) as nucleon partner, we derive effective Lagrangians that describe the decay of N(1710) into N pi pi with two pions in s- or p-wave. It is found that the self-energies for all members of the antidecuplet are attractive, and the larger strangeness particle is more bound. From two-meson cloud, we obtain about 20 % of the empirical mass splitting between states with different strangeness.

hep-ph↗
arXiv2005

Determining the $Θ^+$ quantum numbers through a Kaon induced reaction

We study the $K^+p\to π^+KN$ reaction with kinematical condition suited to the production of the $Θ^+$ resonance. It is shown that in this reaction with the polarization experiment, a combined consideration of the strength at the peak and the angular dependence of cross section can help determine the $Θ^+$ quantum numbers.

nucl-th↗
arXiv2004

Nonpolar optical scattering of positronium in magnesium fluoride

We report the results of the analysis of the temperature broadening of the momentum distribution of delocalized Positronium (Ps) in Magnesium Fluoride in terms of optical deformation-potential scattering model (long-wavelength optical phonons). The Ps optical deformation-potential coupling constant $D_{o}$ in MgF$_{2}$ has been determined to be $(1.8\pm0.3)\times10^{9}$ eV/cm. We also show that the Ps momentum distribution is sensitive to second-order phase transitions in those crystals where optical deformation-potential scattering is allowed in one and forbidden in another crystalline phase.

cond-mat.mtrl-sci↗
arXiv2004

Hadronic aspects of exotic baryons

In this talk I look into three different topics, addressing first the possibility that the $Θ^+$ is a bound state of $K πN$, exploiting the results of this study to find out the contribution of two meson and one baryon components in the baryon antidecuplet and in the third place I present results on a new resonant exotic baryonic state which appears as dynamically generated by the Weinberg Tomozawa $ΔK$ interaction.

nucl-th↗
arXiv2004

Detailed Analysis of the Chiral Unitary Model for Meson-Baryon Scattering with Flavor SU(3) Breaking Effects

We study s-wave meson-baryon scattering using the chiral unitary model. We consider $1/2^{-}$ baryon resonances as quasibound states of the low lying mesons ($π,K,η$) and baryons ($N,Λ,Σ,Ξ$). In previous works, the subtraction constants which appear in loop integrals were found to largely depend on the channels, and it was necessary to fit these constants to reproduce the data. In order to extend this model to all channels with fewer parameters, we introduce flavor SU(3) breaking interactions in the framework of chiral perturbation theory. It is found, however, that the observed SU(3) breaking in meson-baryon scattering cannot be explained by the present SU(3) breaking interactions. The role and importance of the subtraction constants in the present framework are discussed.

nucl-th↗
arXiv2004

On the determination of $Θ^+$ quantum numbers and other topics of exotic baryons

In this talk I look into three different topics, addressing first a method to determine the quantum numbers of the $Θ^+$, then exploiting the possibility that the $Θ^+$ is a bound state of $K πN$ and in the third place I present results on a new resonant exotic baryonic state which appears as dynamically generated by the Weinberg Tomozawa $ΔK$ interaction.

hep-ph↗
arXiv2004

Photoproduction of $K^*$ for the study of $Λ(1405)$

The photo-induced $K^*$ vector meson production is investigated for the study of the $Λ(1405)$ resonance. This reaction is particularly suited to the isolation of the second pole in the $Λ(1405)$ region which couples dominantly to the $\bar K N$ channel. We obtain the mass distribution of the $Λ(1405)$ which peaks at 1420 MeV, and differs from the nominal one. Combined with several other reactions, like the $π^- p \to K^0 πΣ$ which favours the first pole, this detailed study will reveal a novel structure of the $Λ(1405)$ state.

nucl-th↗
arXiv2004

Study of $Λ(1405)$ in photoproduction of $K^*$

We investigate the photoproduction of $K^*$ vector meson for the study of the $Λ(1405)$ resonance. The invariant mass distribution of $πΣ$ shows a different shape from the nominal one, peaking at 1420 MeV. This is considered as a consequence of the double pole structure of $Λ(1405)$, predicted in the chiral unitary model. Combined with other reactions, such as $π^- p \to K^0 πΣ$, experimental confirmation of this fact will reveal a novel structure of the $Λ(1405)$ state.

nucl-th↗
arXiv2003

Determining the $Θ^+$ quantum numbers through the $K^+p\to π^+K^+n$ reaction

We study the $K^+p\to π^+K^+n$ reaction with some kinematics suited to the production of the $Θ^+$ resonance recently observed. We show that, independently of the quantum numbers of the $Θ^+$, a resonance signal is always observed in the $K^+$ forward direction. In addition, we also show how a combined consideration of the strength at the peak, and the angular dependence of polarization observables can help determine the $Θ^+$ quantum numbers using the present reaction.

nucl-th↗
arXiv2003

$Λ(1405)$ production in the $π^-p\to K^0πΣ$ reaction

We discuss the mechanisms that lead to $Λ(1405)$ production in the $π^-p\to K^0πΣ$ reaction. The problem has gained renewed interest after different works converge to the conclusion that there are two resonances around the region of 1400 MeV, rather than one, and that they couple differently to the $πΣ$ and $\bar{K}N$ channels. We look at the dynamics of that reaction and find two mechanisms which eventually filter each one of the resonances, leading to very different shapes of the $πΣ$ invariant mass distributions. The combination of the two mechanisms leads to a shape of this distribution compatible with the experimental measurements.

nucl-th↗
arXiv2003

Regulariztion dependence of S=0 and S=-1 meson-baryon system in the chiral unitary model

We investigate the dependence of s-wave meson-baryon scattering amplitudes on different regularizations within the framework of the chiral unitary model. We employ two different regularization schemes, i.e. dimensional and form-factor regulariaztions to tame the divergences in the model. We also study the analytic structures of T-matrices, using those regularization schemes. We find that while the form-factor regularizaion produces almost the same results as the dimensional regularization did, the on-shell approximation is to some extent limited in the case of the form-factor regularization. Having chosen parameters properly, we show that the regularization dependences can be minimized.

hep-ph↗
arXiv2003

Magnetic moments of the N(1535) resonance in the chiral unitary model

We calculate the magnetic moments of the N(1535) resonance using the chiral unitary model, where the resonance is dynamically generated in the scatterings of the lowest-lying mesons and baryons. We obtain the magnetic moments of the resonance as +1.1 and -0.25 for p(1535) and n(1535), respectively, in units of the nuclear magneton. We discuss the origin of these numbers within the chiral unitary model, then we compare the present results with those of the quark model and the chiral doublet model. The possibility to observe the magnetic moments in experiments is also investigated.

nucl-th↗
arXiv2003

Flavor SU(3) breaking effects in the chiral unitary model for meson-baryon scatterings

We examine flavor SU(3) breaking effects on meson-baryon scattering amplitudes in the chiral unitary model. It turns out that the SU(3) breaking, which appears in the leading quark mass term in the chiral expansion, can not explain the channel dependence of the subtraction parameters of the model, which are crucial to reproduce the observed scattering amplitudes and resonance properties.

nucl-th↗
arXiv2000

Pickoff and spin-conversion quenchings of ortho-positronium in oxygen

The quenching processes of the thermalized ortho-positronium(o-Ps) on an oxygen molecule have been studied by the positron annihilation age-momentum correlation techinique(AMOC). The Doppler broadening spectrum of the 511 keV gamma-rays from the 2gamma annihilation of o-Ps in O_2 has been measured as a function of the o-Ps age. The rate of the quenching, consisting of the pickoff and the spin-conversion, is estimated from the positron lifetime spectrum. The ratio of the pickoff quenching rate to the spin-conversion rate is deduced from the Doppler broadening of the 511 keV gamma-rays from the annihilation of the o-Ps. The pickoff parameter ^1Z_eff, the effective number of the electrons per molecule which contribute to the pickoff quenching, for O_2 is determined to be 0.6 +- 0.4. The cross-section for the elastic spin-conversion quenching is determined to be (1.16 +- 0.01) * 10^{-19} cm^2.

physics.atom-ph↗