Bulletin of the American Physical Society
2018 Joint Fall Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 63, Number 18
Friday–Saturday, October 19–20, 2018; University of Houston, Houston, Texas
Session E04: Nuclear Physics |
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Chair: Anthony Timmins, University of Houston Room: Science and Engineering Classroom (SEC) 204 |
Friday, October 19, 2018 4:15PM - 4:39PM |
E04.00001: What makes the proton spin? Invited Speaker: Carl A. Gagliardi For the past 30 years, there has been an intense world-wide effort to understand how the quarks and gluons that make up the proton organize themselves to produce its spin of 1/2 hbar. The primary tool in this quest has been deep-inelastic scattering of polarized electrons and muons off polarized protons. A surprising discovery has been that the spins of the quarks and anti-quarks only contribute ~1/3 of the proton spin. During the past ~15 years, the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has enabled a new, complementary probe, high-energy polarized pp collisions. The RHIC spin program has provided essential new insights, including evidence that the gluons in the proton are polarized and may even contribute a larger fraction of the proton spin than the quarks do. In this talk, I'll discuss several things we've learned from the RHIC spin program, and where we are heading over the next several years. |
Friday, October 19, 2018 4:39PM - 4:51PM |
E04.00002: Freeze-out temperature from net-kaon fluctuations at RHIC Jamie M Stafford, Rene Bellwied, Jacquelyn Noronha-Hostler, Paolo Parotto, Israel Portillo Vazquez, Claudia Ratti We compare the mean-over-variance ratio of the net-kaon distribution calculated within a state-of-the-art hadron resonance gas model to the latest experimental data from the Beam Energy Scan at RHIC by the STAR collaboration. Our analysis indicates that it is not possible to reproduce the experimental results using the freeze-out parameters from the existing combined fit of net-proton and net-electric charge mean-over-variance. The strange mesons need about 10-15 MeV higher temperatures than the light hadrons at the highest collision energies. In view of the future lambda fluctuation measurements, we predict the lambda variance-over-mean and skewness-times-variance at the light and strange chemical freeze-out parameters. We observe that the lambda fluctuations are sensitive to the difference in the freeze-out temperatures established in this analysis. Our results have implications for other phenomenological models in the field of relativistic heavy ion collisions. |
Friday, October 19, 2018 4:51PM - 5:03PM |
E04.00003: Equation of state for QCD with a critical point from the 3D Ising model Paolo Parotto One of the major investigations in heavy ion physics concerns the search for the Quantum Chromodynamics (QCD) critical point, which has stimulated tremendous effort from both theory and experiment. A major role in the theoretical analysis of experimental results is played by hydrodynamical simulations of heavy ion collisions, which need as an input an equation of state (EoS) driving the evolution of the system. Current knowledge of the finite-density QCD equation of state from first principles is limited to a Taylor expansion in the chemical potential. By means of a scaling form for the EoS in the vicinity of the critical point, and a non-universal map to QCD coordinates, we construct a family of equations of state matching state of the art first principle Lattice QCD calculations and including the correct critical behavior, which is the same as the 3D Ising model. This EoS can be readily employed in hydrodynamical simulations of heavy ion collisions at finite density, covering most of the Beam Energy Scan (BES) range at the Relativistic Heavy Ion Collider (RHIC). The impact on observable quantities related to critical behavior is studied. This contribution reports on work done within the Fluctuations/Equation of State working group of the BEST Collaboration. |
Friday, October 19, 2018 5:03PM - 5:15PM |
E04.00004: Using HECTOR for Cross Section Measurements of 102Pd(p,γ)103Ag Emily Churchman, Anna Simon, Orlando Gomez, Rebeka Kelmar, Craig Reingold, Sean Kelly The High EffiCiency TOtal absorption spectrometeR (HECTOR) consists of 16 scintillating crystals that are made of thallium-doped sodium iodide (NaI(Tl)). Each of the crystals is coupled to two photomultiplier tubes (PMT) and the detector is oriented to create a cubic array surrounding a target. This cubic array orientation allows for simultaneous measurements of the individual gamma (γ) rays produced during the de-excitation of the reaction products, creating a coverage of nearly 4π steradian. HECTOR was constructed to measure capture reactions relevant for the nucleosynthesis process at low energies. The work presented here focuses on a (p,γ) reaction on 102Pd, one of the p-nuclei produced during the p-process. The experiment was conducted at the University of Notre Dame using the FN tandem accelerator at the Nuclear Science Lab. A highly enriched 102Pd target was bombarded with a proton beam at energies between 3.5-8 MeV in 200 keV steps. The measured cross section is compared with experimental data found in literature and theoretical models. |
Friday, October 19, 2018 5:15PM - 5:27PM |
E04.00005: Decay energy spectra of radioactive nuclei Rafael de la Madrid A Gamow-state formula to calculate the decay energy spectrum of a resonance is presented. The formula is applied to the neutron-unbound Oxygen-25. |
Friday, October 19, 2018 5:27PM - 5:39PM |
E04.00006: The Extent and Observable Properties of Nuclear Pasta in Neutron Star Crusts William G Newton, Jirina Rikovska Stone, Mark Kaltenborn, Sarah Cantu, Shuxi Wang A layer of nuclear soft condensed matter called nuclear pasta is predicted to mediate the crust-core transition in neutron stars. We present detailed 3D quantum calculations of nuclear pasta in neutron star crusts and proto-neutron stars. We find that nuclear pasta occurs at lower densities than predicted in semi-classical or classical models, and we predict that over 50% of the mass of a neutron star crust is taken up by nuclear pasta independent of uncertainties in the nuclear equation of state. We show that nuclear pasta likely co-exists with spherical nuclei at the lowest densities, and that multiple phases of pasta likely coexist at higher densities. |
Friday, October 19, 2018 5:39PM - 5:51PM |
E04.00007: Development and Validation of ACTYS, an Activation Analysis software Ishwita Saikia Nuclear reactors require very precise computer software in order to run effectively. I will introduce one such software suite, called ACTYS, which has been developed as part of a long term plan of developing a 3-D nuclear activation software. At present, it predicts the materials’ decay chains and radiological parameters (activity, contact dose, decay heat, gamma source spectra etc). Additionally ACTYS has a module to classify radiological waste. ACTYS is based on a linear chain solution method for the coupled Bateman system and performs favourably as compared with a well-established multi-purpose code system called FISPACT-2007. |
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