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論文

Nuclear structure in parity doublet model

Mun, M.-H.*; Shin, I. J.*; Paeng, W.-G.*; 原田正康*; Kim, Y.*

European Physical Journal A, 59(7), p.149_1 - 149_6, 2023/07

https://doi.org/10.1140/epja/s10050-023-01064-x

被引用回数：0 パーセンタイル：0.02(Physics, Nuclear)

Using an extended parity doublet model with the hidden local symmetry, we study some properties of nuclei in the mean field approximation to see if the parity doublet model could reproduce nuclear properties and also to estimate the value of the chiral invariant nucleon mass $_{0}$ preferred by nuclear structure. We first determine our model parameters using the inputs from free space and from nuclear matter properties. Then, we study some basic nuclear properties such as the nuclear binding energy with several different choices of the chiral invariant mass. We observe that our results approach the experimental values as $_{0}$ is increased until $_{0}$ = 700 MeV and start to deviate more from the experiments afterwards with m0 larger than $_{0}$ = 700 MeV. From this observation, we conclude that $_{0}$ = 700 MeV is preferred by nuclear properties. We then calculate some properties of several selected nuclei with $_{0}$ = 700 MeV and compare them with experiments. Finally, we study the neutron-proton mass difference in some nuclei.

論文

Inverse mass ordering of light scalar mesons in the Nambu-Jona-Lasinio model

西園寺貴公*; 慈道大介*; 原田正康*

Progress of Theoretical and Experimental Physics (Internet), 2023(3), p.033D01_1 - 033D01_18, 2023/03

https://doi.org/10.1093/ptep/ptad028

被引用回数：1 パーセンタイル：0.01(Physics, Multidisciplinary)

The masses of the low-lying scalar mesons are investigated in the three-flavor Nambu-Jona-Lasinio (NJL) model by treating the scalar mesons as composite objects of a quark and an antiquark. It is known that a simple picture fails to reproduce the so-called inverse mass ordering for the scalar mesons. Recently a new mechanism to reproduce the observed mass spectrum of the scalar mesons was proposed in a linear sigma model by introducing flavor symmetry breaking induced by the U(1) axial anomaly. Motivated by this proposal, we examine whether this new mechanism also works in the NJL model. By calculating the scalar meson masses, we find that the NJL model reproduces the observed mass ordering with sufficient strength of the new term. With this mechanism, it turns out that the constituent strange quark mass becomes degenerate to that of the up and down quarks if the inverse mass ordering is reproduced. We also discuss the scalar diquark masses to check the consistency of the degeneracy of the constituent quark masses with the light baryon masses.

論文

Chiral restoration of nucleons in neutron star matter; Studies based on a parity doublet model

南川拓哉*; Gao, B.*; 古城徹*; 原田正康*

Symmetry (Internet), 15(3), p.745_1 - 745_30, 2023/03

https://doi.org/10.3390/sym15030745

被引用回数：4 パーセンタイル：67.47(Multidisciplinary Sciences)

We review the chiral variant and invariant components of nucleon masses and the con- sequence of their existence on the chiral restoration in extreme conditions, particularly in neutron star matter.

論文

Impacts of the anomaly on nuclear and neutron star equation of state based on a parity doublet model

Gao, B.*; 南川拓哉*; 古城徹*; 原田正康*

Physical Review C, 106(6), p.065205_1 - 065205_14, 2022/12

https://doi.org/10.1103/PhysRevC.106.065205

被引用回数：3 パーセンタイル：49.92(Physics, Nuclear)

We examine the role of the U(1) $_{A}$ anomaly in a parity doublet model of nucleons which include the chiral variant and invariant masses. Our model expresses the U(1) $_{A}$ anomaly by the Kobayashi-Maskawa-'t Hooft (KMT) interaction in the mesonic sector. After examining the roles of the KMT term in vacuum, we discuss its impacts on nuclear equations of state (EOS). The U(1) $_{A}$ anomaly increases the masses of the ' and mesons and enhances the chiral symmetry breaking. Also, the U(1) $_{A}$ anomaly enlarges the energy difference between chiral symmetric and symmetry broken vacuum; in turn, the chiral restoration at high density adds a larger energy density (often referred as a bag constant) to EOSs than in the case without the anomaly, leading to softer EOSs. Including these U(1) $_{A}$ effects, we update the previously constructed unified equations of state that interpolate the nucleonic EOS at $_{B}$ 2 $_{0}$ ( $_{0}$ = 0.16 fm $^{-3}$ ; nuclear saturation density) and quark EOS at $_{B}$ 5 $_{0}$ . The unified EOS is confronted with the observational constraints on the masses and radii of neutron stars. The softening of EOSs associated with the (1) anomaly reduces the overall radii, relaxing the previous constraint on the chiral invariant mass $_{0}$ . Including the attractive nonlinear - coupling for the reduced slope parameter in the symmetry energy, our new estimate is 400 MeV $_{0}$ 700 MeV, with $_{0}$ smaller than our previous estimate by 200 MeV.