arXiv subjects

M. Kohno

Publications and source records attributed to M. Kohno.

At least 37 records · Page 2Linked to original sources

arXiv2016

Spatial variations of PAH properties in M17SW revealed by Spitzer/IRS spectral mapping

We present $Spitzer$/IRS mid-infrared spectral maps of the Galactic star-forming region M17 as well as IRSF/SIRIUS Br$γ$ and Nobeyama 45-m/FOREST $^{13}$CO ($J$=1--0) maps. The spectra show prominent features due to polycyclic aromatic hydrocarbons (PAHs) at wavelengths of 6.2, 7.7, 8.6, 11.3, 12.0, 12.7, 13.5, and 14.2 $μ$m. We find that the PAH emission features are bright in the region between the HII region traced by Br$γ$ and the molecular cloud traced by $^{13}$CO, supporting that the PAH emission originates mostly from photo-dissociation regions. Based on the spatially-resolved $Spitzer$/IRS maps, we examine spatial variations of the PAH properties in detail. As a result, we find that the interband ratio of PAH 7.7 $μ$m/PAH 11.3 $μ$m varies locally near M17SW, but rather independently of the distance from the OB stars in M17, suggesting that the degree of PAH ionization is mainly controlled by local conditions rather than the global UV environments determined by the OB stars in M17. We also find that the interband ratios of the PAH 12.0 $μ$m, 12.7 $μ$m, 13.5 $μ$m, and 14.2 $μ$m features to the PAH 11.3 $μ$m feature are high near the M17 center, which suggests structural changes of PAHs through processing due to intense UV radiation, producing abundant edgy irregular PAHs near the M17 center.

astro-ph.GA↗

arXiv2015

Nuclear saturation in lowest-order Brueckner theory with two- and three-nucleon forces in view of chiral effective field theory

The nuclear saturation mechanism is discussed in terms of two-nucleon and three-nucleon interactions in chiral effective field theory (Ch-EFT), using the framework of lowest-order Brueckner theory. After the Coester band, which is observed in calculating saturation points with various nucleon-nucleon (NN) forces, is revisited using modern NN potentials and their low-momentum equivalent interactions, detailed account of the saturation curve of the Ch-EFT interaction is presented. The three-nucleon force (3NF) is treated by reducing it to an effective two-body interaction by folding the third nucleon degrees of freedom. Uncertainties due to the choice of the 3NF low-energy constants $c_D$ and $c_E$ are discussed. The reduction of the cutoff-energy dependence of the NN potential is explained by demonstrating the effect of the 3NF in the $^1$S$_0$ and $^3$S$_1$ states.

nucl-th↗

arXiv2014

Experimental confirmation of spin gap in antiferromagnetic alternating spin-3/2 chain substances RCrGeO5 (R = Y or 154Sm) by inelastic neutron scattering experiments

A spin-singlet ground state with a spin gap has been discovered in antiferromagnetic spin chain substances when the spin value is 1/2, 1 or 2. To find spin gap (singlet-triplet) excitations in spin-3/2 chain substances, we performed inelastic neutron scattering and magnetization measurements on {\it R}CrGeO$_5$ ({\it R} = Y or Sm) powders. As expected, we observed spin gap excitations and the dispersion relation of the lowest magnetic excitations. We proved that the spin system of Cr$^{3+}$ was an antiferromagnetic alternating spin-3/2 chain.

cond-mat.str-el↗

arXiv2013

Nuclear and neutron matter $G$-matrix calculations with Ch-EFT potential including effects of three-nucleon interaction

Energies of symmetric nuclear matter and neutron matter are evaluated in the lowest order Bruekner theory using the Ch-EFT potential including effects of the three-nucleon force (3NF). The 3NF is first reduced to density-dependent nucleon-nucleon (NN) force by folding single-nucleon degrees of freedom in infinite matter. Adding the reduced NN force to the initial NN force and applying a partial-wave expansion, we perform $G$-matrix calculations in pure neutron matter as well as in symmetric nuclear. We obtain the saturation curve which is close to the empirical one. It is explicitly shown that the cutoff-energy dependence of the calculated energies is substantially reduced by including the 3NF. Characters of the 3NF contributions in separate spin and isospin channels are discussed. Calculated energies of the neutron matter are very similar to those used in the literature for considering neutron star properties.

nucl-th↗

arXiv2012

Strength of reduced two-body spin-orbit interaction from chiral three-nucleon force

The contribution of a chiral three-nucleon force to the strength of an effective spin-orbit coupling is estimated. We first construct a reduced two-body interaction by folding one-nucleon degrees of freedom of the three-nucleon force in nuclear matter. The spin-orbit strength is evaluated by a Scheerbaum factor obtained by the $G$-matrix calculation in nuclear matter with the two-nucleon interaction plus the reduced two-nucleon interaction. The problem of the insufficiency of modern realistic two-nucleon interactions to account for the empirical spin-orbit strength is resolved. It is also indicated that the spin-orbit coupling is weaker in the neutron-rich environment. Because the spin-orbit component from the three-nucleon force is determined by the low-energy constants fixed in the two-nucleon sector, there is little uncertainty in the present estimation.

nucl-th↗

arXiv2012

$^4$He energies and radii by the coupled-cluster method with many-body average potential

The reformulated coupled-cluster method (CCM), in which average many-body potentials are introduced, provides a useful framework to organize numerous terms appearing in CCM equations, which enables us to clarify the structure of the CCM theory and physical importance of various terms more easily. We explicitly apply this framework to $^4$He, retaining one-body and two-body correlations as the first illustrating attempt. Numerical results with using two modern nucleon-nucleon interactions (AV18 and CD-Bonn) and their low-momentum interactions are presented. The characters of short-range and many-body correlations are discussed. Although not considered explicitly, the expression of the ground-state energy in the presence of a three-nucleon force is given.

nucl-th↗

arXiv2009

Comparative study of hyperon-nucleon interactions of quark model and chiral effective field theory by low-momentum equivalent interactions and $G$ matrices

Hyperon-nucleons interactions constructed by two frameworks, the Kyoto-Niigata SU$_6$ quark model and the chiral effective field theory, are compared by investigating equivalent interactions in a low-momentum space and in addition by calculating hyperon single-particle potentials in the lowest-order Brueckner theory in symmetric nuclear matter. Two descriptions are shown to give similar matrix elements in most channels after renormalizing high momentum components. Although the range of the $ΛN$ interaction is different in two potentials, the $Λ$ single-particle potential in nuclear matter is very similar. The $Σ$-nucleus and $Ξ$-nucleus potentials are also found to be similar. These predictions are to be confronted with forthcoming experimental data.

nucl-th↗

arXiv2009

The Brieva-Rook Localization of the Microscopic Nucleon-Nucleus Potential

The nonlocality of the microscopic nucleon-nucleus optical potential is commonly localized by the Brieva-Rook approximation. The validity of the localization is tested for the proton+$^{90}$Zr scattering at the incident energies from 65 MeV to 800 MeV. The localization is valid in the wide incident-energy range.

nucl-th↗

arXiv2009

Localized $N, Λ, Σ$, and $Ξ$ Single-Particle Potentials in Finite Nuclei Calculated with $SU_6$ Quark-Model Baryon-Baryon Interactions

Localized single-particle potentials for all octet baryons, $N$, $Λ$, $Σ$, and $Ξ$, in finite nuclei, $^{12}$C, $^{16}$O, $^{28}$Si, $^{40}$Ca, $^{56}$Fe, and $^{90}$Zr, are calculated using the quark-model baryon-baryon interactions. $G$-matrices evaluated in symmetric nuclear matter in the lowest order Brueckner theory are applied to finite nuclei in local density approximation. Non-local potentials are localized by a zero-momentum Wigner transformation. Empirical single-particle properties of the nucleon and the $Λ$ hyperon in nuclear medium have been known to be explained semi-quantitatively in the LOBT framework. Attention is focused in the present consideration on predictions for the $Σ$ and $Ξ$ hyperons. The unified description for the octet baryon-baryon interactions by the SU$_6$ quark-model enables us to obtain less ambiguous extrapolation to the $S=-1$ and $S=-2$ sectors based on the knowledge in the $NN$ sector than other potential models. The $Σ$ mean field is shown to be weakly attractive at the surface, but turns to be repulsive inside, which is consistent with the experimental evidence. The $Ξ$ hyperon s.p. potential is also attractive at the nuclear surface region, and inside fluctuates around zero. Hence $Ξ$ hypernuclear bound states are unlikely. We also evaluate energy shifts of the $Σ^-$ and $Ξ^-$ atomic levels in $^{28}$Si and $^{56}$Fe, using the calculated s.p. potentials.

nucl-th↗

arXiv2008

P-wave Lambda N - Sigma N coupling and the spin-orbit splitting of 9 Lambda Be

We reexamine the spin-orbit splitting of 9 Lambda Be excited states in terms of the SU_6 quark-model baryon-baryon interaction. The previous folding procedure to generate the Lambda alpha spin-orbit potential from the quark-model Lambda N LS interaction kernel predicted three to five times larger values for Delta E_{ell s}=E_x(3/2^+)-E_x(5/2^+) in the model FSS and fss2. This time, we calculate Lambda alpha LS Born kernel, starting from the LS components of the nuclear-matter G-matrix for the Lambda hyperon. This framework makes it possible to take full account of an important P-wave Lambda N - Sigma N coupling through the antisymmetric LS^{(-)} force involved in the Fermi-Breit interaction. We find that the experimental value, Delta E^{exp}_{ell s}=43 pm 5 keV, is reproduced by the quark-model G-matrix LS interaction with a Fermi-momentum around k_F=1.0 fm^{-1}, when the model FSS is used in the energy-independent renormalized RGM formalism.

nucl-th↗

arXiv2008

n alpha Resonating-Group Calculation with a Quark-Model G-Matrix NN Interaction

We calculate n alpha phase-shifts and scattering observables in the resonating-group method, using the nuclear-matter G-matrix of an SU_6 quark-model NN interaction. The G-matrix is generated in the recent energy-independent procedure of the quark-model NN interaction with the continuous prescription for intermediate spectra, by assuming an appropriate Fermi momentum k_F=1.2 fm^-1. The n alpha RGM interaction kernels are evaluated with explicit treatments of the nonlocality and momentum dependence of partial-wave G-matrix components. The momentum dependence of the G-matrix components is different for each of the nucleon-exchange and interaction types. Without introducing any artificial parameters except for k_F, the central and spin-orbit components of the n alpha Born kernel are found to have reasonable strengths under the assumption of a rigid translationally invariant shell-model wave function of the alpha-cluster. The characteristic behaviors of three different exchange terms, corresponding to knockout, heavy-particle pickup and nucleon-rearrangement processes, are essentially the same between the case of previous local effective NN forces and the case of nonlocal G-matrix NN interactions.

nucl-th↗

arXiv2007

Equivalent hyperon-nucleon interactions in low-momentum space

Equivalent interactions in a low-momentum space for the $ΛN$, $ΣN$ and $ΞN$ interactions are calculated, using the SU$_6$ quark model potential as well as the Nijmegen OBEP model as the input bare interaction. Because the two-body scattering data has not been accumulated sufficiently to determine the hyperon-nucleon interactions unambiguously, the construction of the potential even in low-energy regions has to rely on a theoretical model. The equivalent interaction after removing high-momentum components is still model dependent. Because this model dependence reflects the character of the underlying potential model, it is instructive for better understanding of baryon-baryon interactions in the strangeness sector to study the low-momentum space $YN$ interactions.

nucl-th↗

arXiv2007

Addendum: Triton and hypertriton binding energies calculated from SU_6 quark-model baryon-baryon interactions

Previously we calculated the binding energies of the triton and hypertriton, using an SU_6 quark-model interaction derived from a resonating-group method of two baryon clusters. In contrast to the previous calculations employing the energy-dependent interaction kernel, we present new results using a renormalized interaction, which is now energy independent and reserves all the two-baryon data. The new binding energies are slightly smaller than the previous values. In particular the triton binding energy turns out to be 8.14 MeV with a charge-dependence correction of the two-nucleon force, 190 keV, being included. This indicates that about 350 keV is left for the energy which is to be accounted for by three-body forces.

nucl-th↗

arXiv2006

Lambda alpha, Sigma alpha and Xi alpha potentials derived from the SU6 quark-model baryon-baryon interaction

We calculate Lambda alpha, Sigma alpha and Xi alpha potentials from the nuclear-matter G-matrices of the SU6 quark-model baryon-baryon interaction. The alpha-cluster wave function is assumed to be a simple harmonic-oscillator shell-model wave function. A new method is proposed to derive the direct and knock-on terms of the interaction Born kernel from the hyperon-nucleon G-matrices, with explicit treatments of the nonlocality and the center-of-mass motion between the hyperon and alpha. We find that the SU6 quark-model baryon-baryon interactions, FSS and fss2, yield a reasonable bound-state energy for 5 He Lambda, -3.18 -- -3.62 MeV, in spite of the fact that they give relatively large depths for the Lambda single-particle potentials, 46 -- 48 MeV, in symmetric nuclear matter. An equivalent local potential derived from the Wigner transform of the nonlocal Lambda alpha kernel shows a strong energy dependence for the incident Lambda-particle, indicating the importance of the strangeness-exchange process in the original hyperon-nucleon interaction. The Sigma alpha and Xi alpha potentials are repulsive with the attractive isospin I=1/2 (Sigma alpha) and I=0 (Xi alpha) components and the repulsive I=3/2 (Sigma alpha) and I=1 (Xi alpha) components.

nucl-th↗

arXiv2006

Semiclassical Distorted Wave Model Analysis of the $(π^-,K^+)$ $Σ$ Formation Inclusive Spectrum

$(π^-,K^+)$ hyperon production inclusive spectra with $p_π=1.2$ GeV/c measured at KEK on $^{12}$C and $^{28}$Si are analyzed by the semiclassical distorted wave model. Single-particle wave functions of the target nucleus are treated using Wigner transformation. This method is able to account for the energy and angular dependences of the elementary process in nuclear medium without introducing the factorization approximation frequently employed. Calculations of the $(π^+,K^+)$ $Λ$ formation process, for which there is no free parameter since the $Λ$ s.p. potential is known, demonstrate that the present model is useful to describe inclusive spectra. It is shown that in order to account for the experimental data of the $Σ^-$ formation spectra a repulsive $Σ$-nucleus potential is necessary whose magnitude is not so strong as around 100 MeV previously suggested.

nucl-th↗

arXiv2006

Analysis of (K^-,K^+) inclusive spectrum with semiclassical distorted wave model

The inclusive K^+ momentum spectrum in the 12C(K^-,K^+) reaction is calculated by the semiclassical distorted wave (SCDW) model, including the transition to the Ξ^- bound state. The calculated spectra with the strength of the Ξ^--nucleus potential -50, -20, and +10 MeV are compared with the experimental data measured at KEK with p_{K^-}=1.65 GeV/c. The shape of the spectrum is reproduced by the calculation. Though the inclusive spectrum changes systematically depending on the potential strength, it is not possible to obtain a constraint on the potential from the present data. The calculated spectrum is found to have strong emission-angle dependence. We also investigate the incident K^- momentum dependence of the spectrum to see the effect of the Fermi motion of the target nucleons which is explicitly treated in the SCDW method.

nucl-th↗

arXiv2004

Strength of the $Σ$ Single-Particle Potential in Nuclei From Semiclassical Distorted Wave Model Analysis of $(π^-,K^+)$ Inclusive Spectrum

Semiclassical distorted wave model is developed to describe $(π^-,K^+)$ inclusive spectra related to $Σ^-$-formation measured at KEK with $p_π=1.2$ GeV/c. The shape and magnitude of the spectrum on $^{28}$Si target are satisfactorily reproduced by a repulsive $Σ$-nucleus potential, the strength of which is of the order of 30$\sim$50 MeV. This strength is not so strong as more than 100 MeV suggested by the estimation presented in the report of the experiment.

nucl-th↗

arXiv2004

Faddeev Calculation of the Hypertriton using the SU_6 Quark-Model Nucleon-Nucleon and Hyperon-Nucleon Interactions

Quark-model nucleon-nucleon and hyperon-nucleon interactions by the Kyoto- Niigata group are applied to the hypertriton calculation in a new three-cluster Faddeev formalism using the two-cluster resonating-group method kernels. The most recent model, fss2, gives a reasonable result similar to the Nijmegen soft-core model NSC89, except for an appreciable contributions of higher partial waves.

nucl-th↗