Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session 2WAA: Nuclear Equation of State in Context of Neutron Star Merger Event I |
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Chair: Akira Ohnishi, Yukawa Institute for Theoretical Physics, Kyoto Univesity Room: Hilton Kona 4 |
Tuesday, October 23, 2018 2:00PM - 2:30PM |
2WAA.00001: Gravitational waves and the equation of state of binary compact stars Invited Speaker: Luca Baiotti I will present a review of methods for inferring knowledge of the equation of state of compact stars through the analysis of gravitational waves emitted by mergers of compact-star binaries. I will also talk about current results obtained through the analysis of GW170817. |
Tuesday, October 23, 2018 2:30PM - 3:00PM |
2WAA.00002: Characteristics of the nuclear equation of state inferred from the binary neutron star merger Invited Speaker: Farrukh Fattoyev The historical first detection of a binary neutron star (BNS) merger by the LIGO-Virgo Collaboration has provided fundamental new insights into the nature of dense neutron-rich nuclear matter. By using a set of realistic models of the equation of state (EOS) that yield an accurate description of the properties of finite nuclei, support neutron stars of two solar masses, and provide a Lorentz covariant extrapolation to dense matter, we confront their predictions against the measured tidal deformability from the BNS merger. Since the gravitational-wave signal is sensitive to the underlying EOS, limits on the tidal deformability inferred from the observation translate into constraints on the bulk properties of the EOS of neutron-rich matter, such as the density dependence of the nuclear symmetry energy. In particular, we infer the density slope of the symmetry energy to be $L \lesssim 80$ MeV, which is closely related to the pressure of pure neutron matter at saturation density. Given the sensitivity of the laboratory observable, the neutron-skin thickness of $^{208}$Pb, to the pressure of neutron-rich matter we infer a corresponding upper limit to be about $R_{\rm skin}^{208} \lesssim 0.25$ fm. Similarly, this measurement translates into an upper constraint on the astrophysical observable of a neutron-star radius of a 1.4 solar mass neutron star, $R_{1.4} \lesssim 13.76$ km. We will further discuss observational implications of future nuclear experiments on the dynamics of BNS merger and properties of the neutron star core. |
Tuesday, October 23, 2018 3:00PM - 3:30PM |
2WAA.00003: Symmetry energy from electric dipole response of nuclei Invited Speaker: Atsushi Tamii The response of nuclei against external electromagnetic field is of fundamental importance. Among the various external fields, the electric dipole (E1) field induces isovector response that is sensitive to the symmetry energy of the nuclear equation of state. The knowledge of the symmetry energy is indispensable for the study of the neutron-star properties including the process of their merger. The density dependence of the symmetry energy has also a strong correlation with the neutron-skin thickness of heavy neutron-rich nuclei. The full E1 response was, however, not determined well. We have developed an experimental method, employing high-resolution proton inelastic scattering at very forward angles, that is suitable for extracting the full E1 response across the neutron separation energy, covering the PDR and the giant dipole resonance (GDR). The missing mass spectroscopy method enabled us to probe the total strength independently of the decay channels. Multipole decomposition and spin-transfer analyses allowed the extraction of the strength including contributions from unresolved small strengths. The method has been applied to 208Pb, 120Sn, 48Ca and other representative stable nuclei. The full E1 strength distributions were extracted for the excitation energies from 5 to ~20 MeV. The static electric-dipole-polarizabilities were precisely determined by applying the inversely-energy-weighted sum-rule of the E1 strength. Constraint bands on the symmetry energy parameters were determined with a help of mean-field model calculations. The method has been expanded for the studies of PDRs, gamma-strength functions, and nuclear level-densities. Coincidence measurements of the gamma decay are progressing. I will report on the recent progress on the study of the E1 response of nuclei especially for the works relevant to the symmetry energy. |
Tuesday, October 23, 2018 3:30PM - 4:00PM |
2WAA.00004: COFFEE BREAK
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