Probing the Symmetry Energy with the Spectral Pion Ratio

Estee, J.; Lynch, W. G.; Tsang, C. Y.; Barney, J.; Jhang, G.; Tsang, M.B.; Wang, R; Kaneko, M.; Lee, J W; Isobe, T.; Kurata-Nishimura, M.; Murakami, T.; Ahn, D. S.; Atar, L.; Aumann, T.; Baba, H.; Boretzky, K.; Brzychczyk, J.; Cerizza, G.; Chiga, N.; Fukuda, N.; Gašparić, I.; Hong, B.; Horvat, A.; Ieki, K.; Inabe, N.; Kim, Y J; Kobayashi, Toshio; Kondo, Y.; Lasko, P.; Lee, H S; Leifels, Y.; Łukasik, J.; Manfredi, J.; McIntosh, A. B.; Morfouace, P.; Nakamura, Takashi; Nakatsuka, N.; Nishimura, S.; Otsu, H.; Pawłowski, P.; Pelczar, K.; Rossi, D.; Sakuraï, H.; Santamaria, C.; Sato, Hiromi; Scheit, H.; Shane, R.; Shimizu, Y.; Simon, H.; Snoch, A.; Sochocka, A.; Sumikama, T.; Suzuki, Hiroshi; Suzuki, D.; Takeda, Hiroyuki; Tangwancharoen, S.; Toernqvist, H.; Togano, Y.; Zhang, Xiao; Yennello, S. J.; Zhang, Y; π<, mi>; Rit<, mi>; mrow,; Cozma, M.D.

doi:10.1103/physrevlett.126.162701

Cited by 127 publications

(68 citation statements)

References 53 publications

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“…Indeed, there are many interesting results in the literature. In particular, we noticed that the fiducial value of L ≈ 57.7 ± 19 MeV at a 68% confidence level from the 24 new analyses of NS observables since GW170817, as well as the L = 58.9 ± 16 MeV from the 2013 survey of 29 analyses and the L = 58.7 ± 28.1 MeV from the 2016 survey of 53 analyses were all consistent with the latest report of L between 42 and 117 MeV from studying the pion spectrum ratio in heavy-ion collision in an experiment performed at RIKEN [83], but in serious tension with the implications of both the PREX-I and PREX-II experiments measuring the size of neutron skin in 208 Pb using parity violating electron scatterings. The PREX-II experiment found very recently a neutron skin in 208 Pb of size R n − R p = 0.283 ± 0.071 fm.…”

Section: Updated Systematics Of Symmetry Energy Parameters At ρ 0 After Incorporating the Results Of Recent Analyses Of Neutron Star Obsesupporting

confidence: 85%

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Cai²,

Wang

et al. 2021

Universe

146

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The density dependence of nuclear symmetry energy is among the most uncertain parts of the Equation of State (EOS) of dense neutron-rich nuclear matter. It is currently poorly known especially at suprasaturation densities partially because of our poor knowledge about isovector nuclear interactions at short distances. Because of its broad impacts on many interesting issues, pinning down the density dependence of nuclear symmetry energy has been a longstanding and shared goal of both astrophysics and nuclear physics. New observational data of neutron stars including their masses, radii, and tidal deformations since GW170817 have helped improve our knowledge about nuclear symmetry energy, especially at high densities. Based on various model analyses of these new data by many people in the nuclear astrophysics community, while our brief review might be incomplete and biased unintentionally, we learned in particular the following: (1) The slope parameter L of nuclear symmetry energy at saturation density ρ0 of nuclear matter from 24 new analyses of neutron star observables was about L≈57.7±19 MeV at a 68% confidence level, consistent with its fiducial value from surveys of over 50 earlier analyses of both terrestrial and astrophysical data within error bars. (2) The curvature Ksym of nuclear symmetry energy at ρ0 from 16 new analyses of neutron star observables was about Ksym≈−107±88 MeV at a 68% confidence level, in very good agreement with the systematics of earlier analyses. (3) The magnitude of nuclear symmetry energy at 2ρ0, i.e., Esym(2ρ0)≈51±13 MeV at a 68% confidence level, was extracted from nine new analyses of neutron star observables, consistent with the results from earlier analyses of heavy-ion reactions and the latest predictions of the state-of-the-art nuclear many-body theories. (4) While the available data from canonical neutron stars did not provide tight constraints on nuclear symmetry energy at densities above about 2ρ0, the lower radius boundary R2.01=12.2 km from NICER’s very recent observation of PSR J0740+6620 of mass 2.08±0.07M⊙ and radius R=12.2–16.3 km at a 68% confidence level set a tight lower limit for nuclear symmetry energy at densities above 2ρ0. (5) Bayesian inferences of nuclear symmetry energy using models encapsulating a first-order hadron–quark phase transition from observables of canonical neutron stars indicated that the phase transition shifted appreciably both L and Ksym to higher values, but with larger uncertainties compared to analyses assuming no such phase transition. (6) The high-density behavior of nuclear symmetry energy significantly affected the minimum frequency necessary to rotationally support GW190814’s secondary component of mass (2.50–2.67) M⊙ as the fastest and most massive pulsar discovered so far. Overall, thanks to the hard work of many people in the astrophysics and nuclear physics community, new data of neutron star observations since the discovery of GW170817 have significantly enriched our knowledge about the symmetry energy of dense neutron-rich nuclear matter.

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Section: Updated Systematics Of Symmetry Energy Parameters At ρ 0 After Incorporating the Results Of Recent Analyses Of Neutron Star Obsesupporting

confidence: 85%

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Cai²,

Wang

et al. 2021

Universe

146

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“…Claims to the contrary [16,19], therefore, are driven by specific modeling assumptions, which may not be justified. Nevertheless, the large R 208 Pb skin reported in [17] suggests a relatively stiff EoS at low densities, although there are other low-energy experiments (e.g., [20,129,130]) and alternative interpretations of the data [131] that favor softer EoSs. 7 A stiff EoS at low densities may increase the evidence in favor of multiple stable branches, but we expect the effect to be small with current experimental uncertainties.…”

Section: Discussionmentioning

confidence: 97%

Impact of the PSR J0740+6620 radius constraint on the properties of high-density matter

et al. 2021

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X-ray pulse profile modeling of PSR J0740 þ 6620, the most massive known pulsar, with data from the NICER and XMM-Newton observatories recently led to a measurement of its radius. We investigate this measurement's implications for the neutron star equation of state (EoS), employing a nonparametric EoS model based on Gaussian processes and combining information from other x-ray, radio and gravitationalwave observations of neutron stars. Our analysis mildly disfavors EoSs that support a disconnected hybrid star branch in the mass-radius relation, a proxy for strong phase transitions, with a Bayes factor of 6.9. For such EoSs, the transition mass from the hadronic to the hybrid branch is constrained to lie outside ð1; 2Þ M ⊙ . We also find that the conformal sound-speed bound is violated inside neutron star cores, which implies that the core matter is strongly interacting. The squared sound speed reaches a maximum of 0.75 þ0.25 −0.24 c 2 at 3.60 þ2.25 −1.89 times nuclear saturation density at 90% credibility. Since all but the gravitational-wave observations prefer a relatively stiff EoS, PSR J0740 þ 6620's central density is only 3.57 þ1.3 −1.3 times nuclear saturation, limiting the density range probed by observations of cold, nonrotating neutron stars in β-equilibrium.

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“…Efforts to test and constrain χEFT predictions at densities n B n sat using neutronrich nuclei as probes, including improved measurements of neutron-skin thicknesses and dipole polarizabilities, would be valuable and are anticipated in the near-term future [71,72]. Heavy-ion experiments that study collisions of neutron-rich nuclei at intermediate energy can provide guidance for the behavior of the EOS in the density regime of (1 − 2) n sat [62,[73][74][75]. When combined with improved astrophysical constraints on the radius of massive neutron stars, these developments can significantly tighten the lower bound on the maximum speed of sound.…”

Section: Discussionmentioning

confidence: 99%

Large and massive neutron stars: Implications for the sound speed in dense QCD

Drischler,

Han,

Reddy

2021

Preprint

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Probing the Symmetry Energy with the Spectral Pion Ratio

Cited by 127 publications

References 53 publications

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Impact of the PSR J0740+6620 radius constraint on the properties of high-density matter

Large and massive neutron stars: Implications for the sound speed in dense QCD

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