TY - JOUR

T1 - Impacts of the U(1)A anomaly on nuclear and neutron star equation of state based on a parity doublet model

AU - Gao, Bikai

AU - Minamikawa, Takuya

AU - Kojo, Toru

AU - Harada, Masayasu

N1 - Funding Information:
The work of B.G., T.M., and M.H. was supported in part by JSPS KAKENHI Grant No. 20K03927. T.M. was also supported by JST SPRING, Grant No. JPMJSP2125 and T.K. by NSFC Grant No. 11875144 and by the Graduate Program on Physics for the Universe at Tohoku University.
Publisher Copyright:
© 2022 American Physical Society.

PY - 2022/12

Y1 - 2022/12

N2 - 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 η′ and σ 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 nB≤2n0 (n0=0.16fm-3; nuclear saturation density) and quark EOS at nB≥5n0. The unified EOS is confronted with the observational constraints on the masses and radii of neutron stars. The softening of EOSs associated with the U(1) anomaly reduces the overall radii, relaxing the previous constraint on the chiral invariant mass m0. Including the attractive nonlinear ρ-ω coupling for the reduced slope parameter in the symmetry energy, our new estimate is 400MeV≤m0≤700MeV, with m0 smaller than our previous estimate by ≈200 MeV.

AB - 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 η′ and σ 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 nB≤2n0 (n0=0.16fm-3; nuclear saturation density) and quark EOS at nB≥5n0. The unified EOS is confronted with the observational constraints on the masses and radii of neutron stars. The softening of EOSs associated with the U(1) anomaly reduces the overall radii, relaxing the previous constraint on the chiral invariant mass m0. Including the attractive nonlinear ρ-ω coupling for the reduced slope parameter in the symmetry energy, our new estimate is 400MeV≤m0≤700MeV, with m0 smaller than our previous estimate by ≈200 MeV.

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U2 - 10.1103/PhysRevC.106.065205

DO - 10.1103/PhysRevC.106.065205

M3 - Article

AN - SCOPUS:85146135207

SN - 2469-9985

VL - 106

JO - Physical Review C

JF - Physical Review C

IS - 6

M1 - 065205

ER -