arXiv subjects

M. Kohno

Publications and source records attributed to M. Kohno.

At least 19 recordsLinked to original sources

arXiv2026

$\Xi$-deuteron low-energy $s$-wave phase shifts and momentum correlation functions in Faddeev formulation

The low-energy $\Xi$-deuteron scattering is investigated through the solution of Faddeev equations, employing three sets of the currently available representation of the $\Xi$-nucleon interactions. One of these is the chiral NLO interaction specified by the J\"{u}lich group, and the other two are based on the calculations by the HAL-QCD method. The $s$-wave phase shifts in the $J=3/2$ and $J=1/2$ states are presented. Three-body wave functions in coordinate space are constructed from the Faddeev amplitudes in momentum space. These functions are used in the calculation of $\Xi d$ momentum correlation functions. The effects of the deuteron breakup are significant in the $J=3/2$ channel. The differences in the magnitude of the calculated correlation function show the quantitative difference of the $\Xi N$ interactions in the spin-isospin channels. The prospective experimental data on the $\Xi d$ momentum correlation function could contribute to a better description of the $\Xi N$ interactions.

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arXiv2025

The inner rotation curve of the Milky Way

We derived the inner rotation curve (RC) of the Milky Way by applying the terminal velocity method (TVM) to the longitude-velocity diagrams (LVD) made from the large-scale survey data of the Galactic plane in the HI (HI4PI whole sky survey) and CO lines (CfA-Chile 1.2-m Galactic plane survey, Nobeyama 45-m Galactic plane and Galactic Center surveys, and Mopra 22-m southern Galactic plane survey). The derived RC agrees well with the RCs derived from the astrometric measurements of the maser sources by very long baseline interferometer (VLBI) observations and the GAIA result. We combined them to construct a unified RC from $R=0$ to $\sim 25$ kpc and decomposed the curve into bulge, disc and dark halo components with high precision. The dark matter density near the Sun is estimated to be $0.107 \pm 0.003$ GeV cm$^{-3}$. We present the RC as ascii tables for the solar constants of $(R_0,V_0)=(8.178 {\rm kpc}, 235.1 {\rm km/s})$, We also obtained a detailed comparison of the eastern ($l\ge 0^\circ$) and western ($< 0^\circ$) RCs in the HI and CO lines, which allowed the creation of an E/W asymmetry curve of the velocity difference. The E/W asymmetry is fitted by a sinusoidal function of the radius with the amplitude increasing toward the Galactic Center. We consider the possibility of the origin due to a weak bar inside $\sim 4$ kpc.

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arXiv2025

$\Lambda$-deuteron momentum correlation functions incorporating deuteron breakup contributions in Faddeev formulation

The effects of the deuteron breakup are estimated for the $\Lambda$-deuteron momentum correlation function. Faddeev amplitudes in calculating low-energy $\Lambda$-deuteron scattering can provide not only the elastic scattering part but also breakup wave functions in the incident and the rearrangement channels. Calculations are carried out using nucleon-nucleon (NN) and hyperon-nucleon (YN) interactions parametrized in chiral effective field theory. The effects of the breakup in the incident channel are found to be marginally insignificant. Those of the rearrangement channel are not negligible, but not large when the source radius is larger than 2.5 fm. Nevertheless, it is worthwhile to have the information on the magnitude of these effects in analyzing the experimental data.

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arXiv2024

Faddeev calculations of low-energy $\Lambda$-deuteron scattering and momentum correlation function

Faddeev calculations of low-energy $\Lambda$-deuteron elastic scattering are performed up to $E_{cm}=20$ MeV across the deuteron threshold. Phase shifts of the $s$-wave with $J=1/2$ and $J=3/2$ are calculated using strangeness $S=-1$ hyperon-nucleon interactions in chiral effective field theory NLO13 and NLO19 parametrized by the J{\"u}lich-Bonn group. Effective range parameters, such as a scattering length and an effective range, are determined through the calculated phase shifts. $\Lambda$-deuteron momentum correlation functions are evaluated using the $\Lambda$-deuteron relative wave function constructed from half-off-shell $t$-matrices. They are compared with those evaluated using an approximate formula.

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arXiv2023

Contributions of $2\pi$-exchange, $1\pi$-exchange, and contact three-body forces in NNLO ChEFT to $_\Lambda^3$H

Faddeev calculations of hypertriton ($_\Lambda^3$H) separation energy are performed, incorporating all next-to-next-to-leading-order $\Lambda$NN three-body forces (3BFs) in chiral effective field theory: $2\pi$-exchange, $1\pi$-exchange, and contact interactions. The $1\pi$-exchange and contact interactions are rewritten in a form suitable for evaluating partial-wave matrix elements. The $\Lambda$-deuteron folding potentials constructed from these 3BFs are evaluated to demonstrate their contributions to \h3t. The $1\pi$-exchange interaction provides an attractive effect in which the d-state component of the deuteron wave function plays an important role. The attractive contribution tends to cancel the repulsive ones from the $2\pi$-exchange and contact 3BFs. Faddeev calculations show that the net effect of the 3BFs to the \h3t separation energy is small in a range between $-5$ to $+20$ keV, depending on the NN interaction used. Although these results are based on speculative low-energy constants, they can serve as a reference for further investigations.

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arXiv2023

Faddeev Calculation of $_\Lambda^3$H incorporating 2{\pi}-exchange $\Lambda$NN Interaction

Faddeev calculations of hypertriton ($_\Lambda^3$H) separation energy are performed, incorporating $2\pi$-exchange $\Lambda $NN three-baryon force. Repulsive contributions of the three-baryon force in the order of 20 keV are found, depending on the NN interactions employed. The effect is not negligible compared with the small separation-energy of $_\Lambda^3$H.

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arXiv2022

Partial-wave expansion of $\Lambda NN$ three-baryon interactions in chiral effective field theory

An expression of partial wave expansion of three-baryon interactions in chiral effective field theory is presented. The derivation follows the method by Hebeler et al. [Phys. Rev. C{\bf 91}, 044001 (2015)], but the final expression is more general. That is, a systematic treatment of the higher-rank spin-momentum structure of the interaction becomes possible. Using the derived formula, a $\Lambda$-deuteron folding potential is evaluated. This information is valuable for inferring the possible contribution of the $\Lambda NN$ three-baryon forces to the hypertriton as the basis of further studies by sophisticated Faddeev calculations. A microscopic understanding of $\Lambda NN$ three-baryon forces together with two-body $\Lambda N$ interactions is essential for the description of hypernuclei and neutron-star matter.

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arXiv2021

$\Xi$ hyper-nuclear states predicted by NLO chiral baryon-baryon interactions

The $\Xi$ single-particle potential obtained in nuclear matter with the next-to-leading order baryon-baryon interactions in chiral effective field theory is applied to finite nuclei by an improved local-density approximation method. As a premise, phase shifts of $\Xi N$ elastic scattering and the results of Faddeev calculations for the $\Xi NN$ bound state problem are presented to show the properties of the $\Xi N$ interactions in the present parametrization. First, the $\Xi$ states in $^{14}$N are revisited because of the recent experimental progress, including the discussion on the $\Xi N$ spin-orbit interaction that is relevant to the location of the $p$-state. Then the $\Xi$ levels in $^{56}$Fe are calculated. In particular, the level shift which is expected to be measured experimentally in the near future is predicted. The smallness of the imaginary part of the $\Xi$ single-particle potential is explicitly demonstrated.

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arXiv2021

A Kinematic Analysis of the Giant Molecular Complex W3; Possible Evidence for Cloud-Cloud Collisions that Triggered OB Star Clusters in W3 Main and W3(OH)

W3 is one of the most outstanding regions of high-mass star formation in the outer solar circle, including two active star-forming clouds, W3 Main and W3(OH). Based on a new analysis of the $^{12}$CO data obtained at 38$^{\prime\prime}$ resolution, we have found three clouds having molecular mass from 2000 to 8000~$M_\odot$ at velocities, $-50$~km s$^{-1}$, $-43$~km s$^{-1}$, and $-39$~km s$^{-1}$. The $-43$~km s$^{-1}$ cloud is the most massive one, overlapping with the $-39$~km s$^{-1}$ cloud and the $-50$~km s$^{-1}$ cloud toward W3 Main and W3(OH), respectively. In W3 Main and W3(OH), we have found typical signatures of a cloud-cloud collision, i.e., the complementary distribution with/without a displacement between the two clouds and/or a V-shape in the position-velocity diagram. We frame a hypothesis that a cloud-cloud collision triggered the high-mass star formation in each region. The collision in W3 Main involves the $-39$~km s$^{-1}$ cloud and the $-43$~km s$^{-1}$ cloud. The collision likely produced a cavity in the $-43$~km s$^{-1}$ cloud having a size similar to the $-39$~km s$^{-1}$ cloud and triggered the formation of young high-mass stars in IC~1795 2 Myr ago. We suggest that the $-39$~km s$^{-1}$ cloud is still triggering the high-mass objects younger than 1 Myr embedded in W3 Main currently. On the other hand, another collision between the $-50$~km s$^{-1}$ cloud and the $-43$~km s$^{-1}$ cloud likely formed the heavily embedded objects in W3(OH) within $\sim$0.5 Myr ago. The present results favour an idea that cloud-cloud collisions are common phenomena not only in the inner solar circle but also in the outer solar circle, where the number of reported cloud-cloud collisions is yet limited (Fukui et al. 2021, PASJ, 73, S1).

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arXiv2021

Evidence for a Cloud-Cloud Collision in Sh2-233 Triggering the Formation of the High-mass Protostar Object IRAS 05358+3543

We have carried out a new kinematical analysis of the molecular gas in the Sh2-233 region by using the CO $J$ = 2-1 data taken at $\sim$0.5 pc resolution. The molecular gas consists of a filamentary cloud of 5-pc length with 1.5-pc width where two dense cloud cores are embedded. The filament lies between two clouds, which have a velocity difference of 2.6 km s$^{-1}$ and are extended over $\sim$5 pc. We frame a scenario that the two clouds are colliding with each other and compressed the gas between them to form the filament in $\sim$0.5 Myr which is perpendicular to the collision. It is likely that the collision formed not only the filamentary cloud but also the two dense cores. One of the dense cores is associated with the high-mass protostellar candidate IRAS 05358+3543, a representative high-mass protostar. In the monolithic collapse scheme of high mass star formation, a compact dense core of 100 $M_\odot$ within a volume of 0.1 pc radius is assumed as the initial condition, whereas the formation of such a core remained unexplained in the previous works. We argue that the proposed collision is a step which efficiently collects the gas of 100 $M_\odot$ into 0.1 pc radius. This lends support for that the cloud-cloud collision is an essential process in forming the compact high-mass dense core, IRAS 05358+3543.

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arXiv2021

A Realistic Approach to the $\Xi NN$ Bound-State Problem based on Faddeev Equation

The Faddeev equations for the $\Xi NN$ bound-state problem are solved where the three $S$=$-2$ baryon-baryon interactions of J\"ulich-Bonn-M\"unchen chiral EFT, HAL QCD and Nijmegen ESC08c are used. The $T$-matrix $T_{\Xi N, \Xi N}$ obtained within the original $\Lambda\Lambda$-$\Xi N$-$\Sigma\Sigma$ $/$ $\Xi N$-$\Lambda \Sigma$-$\Sigma\Sigma$ coupled-channel framework is employed as an input to the equations. We found no bound state for J\"ulich-Bonn-M\"unchen chiral EFT and HAL QCD but ESC08c generates a bound state with the total isospin and spin-parity $(T,J^{\pi})=(1/2, 3/2^+)$ where the decays into $\Lambda\Lambda N$ are suppressed.

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arXiv2020

A kinematic analysis of the CO clouds toward a reflection nebula NGC 2023 observed with the Nobeyama 45 m telescope; Further evidence for a cloud-cloud collision in the Orion region

We have analyzed new CO($J$ = 1-0) data in the region of a reflection nebula NGC 2023 with a particular focus on the detailed kinematical properties of the molecular gas. The results show that there are two velocity components which indicate signatures of dynamical interaction revealed at a high resolution of 19$''$ (= 0.04 pc). Based on the results we propose a hypothesis that two clouds collided with each other and triggered the formation of the B1.5 star HD 37903 in addition to 20 lower mass stars in two small clusters with a size of 2 pc. Although the previous study favored a scheme of triggering by the HII region (e.g., Mookerjea et al. 2009), the present results show that the effect of the HII region is limited only to the surface of the molecular cloud, and does not contribute to the gas compression and star formation. The present results lend support for the dominant role of cloud-cloud collision in forming high mass stars in addition to $\sim$20 lower mass stars, which are also likely formed by the collision. The present case suggests all the high mass stars in the Orion region are formed by cloud-cloud collision.

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arXiv2019

$\Xi$ hyperons in the nuclear medium described by chiral NLO interactions

Properties of the baryon-baryon interactions in the strangeness $S=-2$ sector of chiral effective field theory at the next-to-leading order (NLO) level are explored by calculating $\Xi$ single-particle potentials in symmetric nuclear matter. The results are transformed to the $\Xi$ potential in finite nuclei by a local-density approximation with convolution by a Gaussian form factor to simulate finite-range effects. The $\Xi$ potential is repulsive in a central region, and attractive in a surface area when the $\Xi$ energy is low. The attractive pocket can lower the $\Xi^-$ $s$ and $p$ atomic states. The obtained binding energies in $^{12}$C and $^{14}$N are found to be conformable with those found in emulsion experiments at Japan's National Laboratory for High Energy Physics (KEK). $K^+$ spectra of $(K^-, K^+)$ $\Xi$ production inclusive processes on $^9$Be and $^{12}$C are also evaluated, using a semi-classical distorted wave method. The absolute values of the cross section are properly reproduced for $^9$Be, but the peak locates at a lower energy position than that of the experimental data. The calculated spectrum of $^{12}$C should be compared with the forthcoming result from the new experiments recently carried out at KEK with better resolution than before. The comparison would be valuable to improve the understanding of the $\Xi N$ interaction, the parametrization of which has still large uncertainties.

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arXiv2019

Ground-state properties of doubly magic nuclei from the unitary-model-operator approach with the chiral two- and three-nucleon forces

The ground-state energies and radii for $^{4}$He, $^{16}$O, and $^{40}$Ca are calculated with the unitary-model-operator approach (UMOA). In the present study, we employ the similarity renormalization group (SRG) evolved nucleon-nucleon ($NN$) and three-nucleon ($3N$) interactions based on the chiral effective field theory. This is the first UMOA calculation with both $NN$ and $3N$ interactions. The calculated ground-state energies and radii are consistent with the recent {\it ab initio} results with the same interaction. We evaluate the expectation values with two- and three-body SRG evolved radius operators, in addition to those with the bare radius operator. With the aid of the higher-body evolution of radius operator, it is seen that the calculated radii tend to be SRG resolution-scale independent. We find that the SRG evolution gives minor modifications for the radius operator.

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arXiv2018

Pauli rearrangement potential for a scattering state with the interaction in chiral effective field theory

The Pauli rearrangement potential given by the second-order diagram is evaluated for a nucleon optical model potential (OMP) with $G$ matrices of the nucleon-nucleon interaction in chiral effective field theory. The results obtained in nuclear matter are applied for $^{40}$Ca in a local-density approximation. The repulsive effect is of the order of 5MeV at the normal density. The density dependence indicates that the real part of the microscopic OMP becomes shallower in a central region, but is barely affected in a surface area. This improves the overall resemblance of the microscopic OMP to the empirical one.

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arXiv2018

FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45-m Telescope (FUGIN) IV: Galactic Shock Wave and Molecular Bow Shock in the 4-kpc Arm of the Galaxy

The FUGIN CO survey with the Nobeyama 45-m Telescope revealed the 3D structure of a galactic shock wave in the tangential direction of the 4-kpc molecular arm. The shock front is located at G30.5+00.0+95 km/s on the up-stream (lower longitude) side of the star-forming complex W43 (G30.8-0.03), and composes a molecular bow shock (MBS) concave to W43, exhibiting an arc-shaped molecular ridge perpendicular to the galactic plane with width $\sim 0^\circ.1$ (10 pc) and vertical length $\sim 1^\circ \ (100\ {\rm pc})$. The MBS is coincident with the radio continuum bow of thermal origin, indicating association of ionized gas and similarity to a cometary bright-rimmed cloud. The up-stream edge of the bow is sharp with a growth width of $\sim 0.5$ pc indicative of shock front property. The velocity width is $\sim 10$ km/s, and the center velocity decreases by $\sim 15$ \kms from bottom to top of the bow. The total mass of molecular gas in MBS is estimated to be $\sim 1.2\times 10^6 <_\odot$ and ionized gas $\sim 2\times 10^4 M_\odot$. The vertical disk thickness increases step like at the MBS by $\sim 2$ times from lower to upper longitude, which indicates hydraulic-jump in the gaseous disk. We argue that the MBS was formed by the galactic shock compression of an accelerated flow in the spiral-arm potential encountering the W43 molecular complex. A bow-shock theory can well reproduce the bow morphology. We argue that molecular bows are common in galactic shock waves not only in the Galaxy but also in galaxies, where MBS are associated with giant cometary HII regions. We also analyzed the HI data in the same region to obtain a map of HI optical depth and molecular fraction. We found a firm evidence of HI-to-H$_{2}$ transition in the galactic shock as revealed by a sharp molecular front at the MBS front.

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arXiv2018

Single-particle potential of the $\Lambda$ hyperon in nuclear matter with chiral effective field theory NLO interactions including effects of YNN three-baryon interactions

Adopting hyperon-nucleon and hyperon-nucleon-nucleon interactions parametrized in chiral effective field theory, single-particle potentials of the $\Lambda$ and $\Sigma$ hyperons are evaluated in symmetric nuclear matter and in pure neutron matter within the framework of lowest order Bruckner theory. The chiral NLO interaction bears strong $\Lambda$N-$\Sigma$N coupling. Although the $\Lambda$ potential is repulsive if the coupling is switched off, the $\Lambda$N-$\Sigma$N correlation brings about the attraction consistent with empirical data. The $\Sigma$ potential is repulsive, which is also consistent with empirical information. The interesting result is that the $\Lambda$ potential becomes shallower beyond normal density. This provides the possibility to solve the hyperon puzzle without introducing ad hoc assumptions. The effects of the $\Lambda$NN-$\Lambda$NN and $\Lambda$NN-$\Sigma$NN three-baryon forces are considered. These three-baryon forces are first reduced to normal-ordered effective two-baryon interactions in nuclear matter and then incorporated in the $G$-matrix equation. The repulsion from the $\Lambda$NN-$\Lambda$NN interaction is of the order of 5 MeV at the normal density, and becomes larger with increasing the density. The effects of the $\Lambda$NN-$\Sigma$NN coupling compensate the repulsion at normal density. The net effect of the three-baryon interactions to the $\Lambda$ single-particle potential is repulsive at higher densities.

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arXiv2017

Discovery of molecular and atomic clouds associated with the gamma-ray supernova remnant Kesteven 79

We carried out $^{12}$CO($J$ = 1-0) observations of the Galactic gamma-ray supernova remnant (SNR) Kesteven 79 using the Nobeyama Radio Observatory 45 m radio telescope, which has an angular resolution of $\sim20$ arcsec. We identified molecular and atomic gas interacting with Kesteven 79 whose radial velocity is $\sim80$ km s$^{-1}$. The interacting molecular and atomic gases show good spatial correspondence with the X-ray and radio shells, which have an expanding motion with an expanding velocity of $\sim4$ km s$^{-1}$. The molecular gas associated with the radio and X-ray peaks also exhibits a high-intensity ratio of CO 3-2/1-0 $>$ 0.8, suggesting a kinematic temperature of $\sim24$ K, owing to heating by the supernova shock. We determined the kinematic distance to the SNR to be $\sim5.5$ kpc and the radius of the SNR to be $\sim8$ pc. The average interstellar proton density inside of the SNR is $\sim360$ cm$^{-3}$, of which atomic protons comprise only $\sim10$ $\%$. Assuming a hadronic origin for the gamma-ray emission, the total cosmic-ray proton energy above 1 GeV is estimated to be $\sim5 \times 10^{48}$ erg.

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