Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session DK: Mini-Symposium on the Nuclear Equation of State and its Astrophysical Applications |
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Chair: Betty Tsang, Michigan State University Room: City Center B |
Thursday, October 26, 2017 10:30AM - 11:06AM |
DK.00001: The EOS and superfluid properties of dense matter from neutron star observations Invited Speaker: Andrew Steiner Neutron stars offer a unique window into a region of the QCD phase diagram which is nearly inaccessible from experiment: matter with temperatures less than or equal to 1 MeV and densities near a few times the nuclear saturation density. In particular, observations of neutron star masses, radii, ages, and surface temperatures are providing constraints on the equation of state of dense matter and the magnitude and density dependence of the gaps. In this talk, I will briefly describe the current status on what we know about these properties of dense matter. I will also describe two of the most important frontiers in dense matter research: the EOS between 1 and 2 times the nuclear saturation density and the composition of the neutron star core. [Preview Abstract] |
Thursday, October 26, 2017 11:06AM - 11:18AM |
DK.00002: Mirror Charge Radii and the Neutron Equation of State Alex Brown The differences in the charge radii of mirror nuclei are shown to be proportional to the neutron skins of neutron-rich nuclei and the corresponding slope of the neutron equation of state near a value of 0.10 neutrons/fm$^{3}$. The neutron skin is important for constraining the neutron equation of state for use in astrophysics. The charge radii of several neutron-rich nuclei are already accurately measured to the accuracy of about 0.005 fm. Experiments at radioactive beam facilities are needed to measure the charge radii of the corresponding proton-rich mirror nuclei to a similar accuracy. It is also shown that neutron skins of nuclei with $ N=Z $ depend upon the value of the neutron EOS at a density of 0.10 neutrons/fm$^{3}$. [Preview Abstract] |
Thursday, October 26, 2017 11:18AM - 11:30AM |
DK.00003: Determination of experimental equation of state at low density W.G. Lynch, M.B. Tsang The density dependence of the nuclear symmetry energy governs many aspects of very neutron rich systems such as neutron stars and heavy nuclei. Many observables and experiments have been designed to probe the symmetry energy in regions below the saturation density. However, analyses of most of these measurements focused on model dependent extrapolations to the symmetry energy ($S_{0}$ or $J$) and its first derivative ($L$) at saturation density, $\rho_{0}$. We show that each observable probes densities below $\rho_{0}$ and illustrate an alternative approach focused on obtaining the symmetry energy at the density most accurately probed by the experiment using published constraints of ($S_{0}$) and ($L$). We obtain new constraints on the density dependence of symmetry energy from 0.2$\rho_{0}$ to 0.8$\rho_{0}$. Specifically, the new constraints at $\rho < 0.5\rho_{0}$ provide important benchmarks for calculations of neutron-rich matter in low-density astrophysical environments. [Preview Abstract] |
Thursday, October 26, 2017 11:30AM - 11:42AM |
DK.00004: Probing the Symetry Energy at supra-saturation density with the S$\pi$RIT Time Projection Chamber Jonathan Barney The S$\pi$RIT Time Projection Chamber (TPC) was designed and constructed at the National Superconducting Cyclotron Laboratory, Texas A&M University, RIKEN and Kyoto University. It was used in a campaign of experiments at the Radioactive Isotope Beam Factory at RIKEN, intended to constrain the symmetry term of the Nuclear Equation of State at around twice saturation density. The commissioning of the S$\pi$RIT TPC was completed in spring 2016, with the experimental campaign also performed in 2016. The experiment is designed especially to compare the ratio of negative and positive pions produced in asymmetric collisions. Four separate Sn beams ($^{132}$Sn, $^{124}$Sn, $^{112}$Sn, $^{108}$Sn) are impinged on isotopically enriched fixed Sn ($^{124}$Sn, $^{112}$Sn) targets, with an energy at about 270 AMeV. Most pions are produced in the central region of the collision and provide an effective probe for the high density region of the collision. I will present preliminary results from the experiments and the on-going efforts to analyze the pion spectra. [Preview Abstract] |
Thursday, October 26, 2017 11:42AM - 11:54AM |
DK.00005: Scaling functions for the Inverse Compressibility near the QCD critical point Roy Lacey The QCD phase diagram can be mapped out by studying fluctuations and their response to changes in the temperature and baryon chemical potential. Theoretical studies~\cite{Stokic:2008jh} indicate that the cumulant ratios $C_n/C_m$ used to characterize the fluctuation of conserved charges, provide a valuable probe of deconfinement and chiral dynamics, as well as for identifying the position of the critical endpoint (CEP) in the QCD phase diagram. The ratio $C_1/C_2$, which is linked to the inverse compressibility, vanishes at the CEP due to the divergence of the net quark number fluctuations at the critical point belonging to the Z(2) universality class~\cite{Stokic:2008jh}. Therefore, it's associated scaling function can give insight on the location of the critical end point, as well as the critical exponents required to assign its static universality class. Scaling functions for the ratio $C_1/C_2$, obtained from net-proton multiplicity distributions for a broad range of collision centralities in Au+Au ($\sqrt{s_{NN}}= 7.7 - 200$ GeV) collisions will be presented and discussed. %\cite{Stokic:2008jh} \bibitem{Stokic:2008jh} B.~Stokic, B.~Friman, and K.~Redlich, %``Kurtosis and compressibility near the chiral phase transition,'' Phys.\ Lett.\ B {\bf 673}, 192 (200 [Preview Abstract] |
Thursday, October 26, 2017 11:54AM - 12:06PM |
DK.00006: Constraining the symmetry energy with heavy-ion collisions and Bayesian analysis C.Y. Tsang, G. Jhang, P. Morfouace, W.G. Lynch, M.B. Tsang To extract constraints on symmetry energy terms in nuclear Equation of State (EoS), data from heavy ion reactions, are often compared to calculations from transport models. As multiple model input parameters are needed in the transport model, it is necessary to do multi-parameter analysis to understand the relationship especially if strong correlations exist among the parameters. In this talk, I will discuss how four symmetry energy parameters, So, (Symmetry energy) and L (slope) at saturation density as well as the nucleon scaler effective mass ( ms*) and the nucleon effective mass splitting, (FI) are obtained by comparing transport mode results with experimental data such as isospin diffusions and n/p spectral ratios using MADAI Bayesian analysis software. Probability of each parameter having a certain value given experimental data can be calculated with Bayes theorem by Markov Chain Monte Carlo integration. Results using single and double ratios of neutron and proton spectra from 124Sn$+$124Sn, 112Sn$+$112Sn collisions at 120 MeV/u as well as isospin diffusion from Sn$+$Sn isotopes, at 50 and 35 MeV/u will be presented. [Preview Abstract] |
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