Bulletin of the American Physical Society
Joint Fall 2017 Meeting of the Texas Section of the APS, Texas Section of the AAPT, and Zone 13 of the Society of Physics Students
Volume 62, Number 16
Friday–Saturday, October 20–21, 2017; The University of Texas at Dallas, Richardson, Texas
Session K6: Nuclear Physics I |
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Chair: Sally Hicks, University of Dallas Room: DGAC 1.135 |
Saturday, October 21, 2017 10:30AM - 10:42AM |
K6.00001: Characterization of ParTI Phoswiches Using Charged Pion Beams Emily Churchman, Andrew Zarrella, Michael Youngs, Sherry Yennello The Partial Truncated Icosahedron (ParTI) detector array consists of 15 phoswiches. Each phoswich is made of two scintillating components -- a thallium-doped cesium iodide (CsI(Tl)) crystal and an EJ-212 scintillating plastic -- coupled to a photomultiplier tube. Both materials have different scintillation times and are sensitive to both charged and neutral particles. The type of particle and amount of energy deposited determine the shape of the scintillation pulse as a function of time. By integrating the fast and slow signals of the scintillation pulses, a ``Fast vs. Slow Integration'' plot can be created that produces particle identification lines based on the energy deposited in the scintillating materials. Four of these phoswiches were taken to the Paul Scherrer Institute (PSI) in Switzerland where $\pi +$, $\pi $-, and proton beams were scattered onto the phoswiches to demonstrate their particle identification (PID) capabilities. Using digitizers to record the detector response waveforms, pions can also be identified by the characteristic decay pulse of the muon daughters. [Preview Abstract] |
Saturday, October 21, 2017 10:42AM - 10:54AM |
K6.00002: Transition Metal Doping Reveals Link between Electron $T_{\mathrm{1}}$ Reduction and $^{\mathrm{13}}$C Dynamic Nuclear Polarization Efficiency Peter Niedbalski, Christopher Parish, Qing Wang, Zahra Hayati, Likai Song, Andre Martins, A. Dean Sherry, Lloyd Lumata Since its invention in 2003, dissolution dynamic nuclear polarization (DNP) has been widely used to increase the weak signal strength of nuclear magnetic resonance (NMR). In this method, polarization is transferred from free electrons to nuclei using microwave irradiation at intermediate magnetic field and cryogenic temperatures and then rapidly dissolved using a superheated solvent. This process requires a source of free radicals, one of the most common being trityl OX063. At low field (3.35 T), polarization using trityl as the polarizing agent can be significantly enhanced by the addition of paramagnetic agents. In order to come to a greater understanding of this process, paramagnetic transition metal ion complexes were used as dopants for $^{\mathrm{13}}$C DNP using trityl. Mn$^{\mathrm{2+}}$-NOTA proved to be beneficial to polarization, while Co$^{\mathrm{2+}}$-NOTA and Cu$^{\mathrm{2+}}$-NOTA had no impact. Electron paramagnetic resonance studies showed that the $T_{\mathrm{1}}$ of trityl was shortened drastically by the manganese additive but remained unchanged with the addition of copper or cobalt. These results confirm the commonly assumed link between electronic $T_{\mathrm{1}}$ and DNP efficiency. [Preview Abstract] |
Saturday, October 21, 2017 10:54AM - 11:06AM |
K6.00003: Magnetic Field Dependent Lifetimes of Hyperpolarized Carboxyl $^{\mathrm{13}}$C at Cryogenic Temperatures Peter Niedbalski, Qing Wang, Christopher Parish, Fatemeh Khashami, Andhika Kiswandhi, Lloyd Lumata Measurement of nuclear spin lattice relaxation times can be challenging, particularly for $^{\mathrm{13}}$C nuclei at cryogenic temperatures. At such conditions, $^{\mathrm{13}}$C has a relatively weak signal strength and very long relaxation time, making conventional methods of measuring $T_{\mathrm{1}}$ extremely time consuming and impractical. However, using a custom-built dynamic nuclear polarization (DNP) polarizer with a sweepable superconducting magnet, the $^{\mathrm{13}}$C $T_{\mathrm{1}}$ at many different magnetic field strengths may be measured relatively rapidly. First, the signal strength of $^{\mathrm{13}}$C NMR is highly enhanced at the polarization field. Then, the magnetic field is ramped to an alternative strength where the relaxation of the hyperpolarized signal is monitored from which $T_{\mathrm{1}}$ may be determined. Four different molecules with carboxyl $^{\mathrm{13}}$C labeling were chosen for study using this process, namely sodium pyruvate, pyruvic acid, sodium acetate, and glycine. Samples were studied between 0.8 and 9 T and the $T_{\mathrm{1}}$ of each of the samples was found to have power law dependence on the magnetic field between $B^{\mathrm{2.35}}$ and $B^{\mathrm{3.1}}$. This strong magnetic field dependence is a result of paramagnetic impurities required for polarization. These measurements are the first of their type and help to further understand dynamic nuclear polarization in the regime of high magnetic field and low temperature. [Preview Abstract] |
Saturday, October 21, 2017 11:06AM - 11:18AM |
K6.00004: $D^{0}$-Hadron Correlations in Azimuth and Pseudorapidity in Au+Au Collisions at $\sqrt{s_{NN}} = 200$ GeV Alexander Jentsch Collisions of ultra-relativistic gold nuclei in the Relativistic Heavy-Ion Collider at BNL produce a hot and dense medium called the Quark-Gluon Plasma (QGP). Two-particle correlations on azimuth ($\phi$) and pseudorapidity ($\eta$) provide a sensitive probe of the dynamics of the QGP. In particular, $\phi$-dependent contributions (e.g. the second-order azimuthal anisotropy) and $\eta$-dependent contributions can be extracted simultaneously. Such correlations have been measured for light-flavor hadrons. Heavy flavor quarks (i.e. charm and bottom) provide unique information about QGP dynamics because they are predominantly formed in the early stage of the collisions. Furthermore, because of their high masses, flavor-dependent parton interactions with the medium (i.e. energy loss, thermalization) can be studied. We will present a measurement of $D^{0}$-hadron correlations in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV from the Solenoidal Tracker at RHIC (STAR) experiment. The $D^{0}$ meson is reconstructed via its hadronic decay channel using the Heavy Flavor Tracker. Through this measurement, we will extract the evolution of the correlation structures as a function of $D^{0}$ transverse momentum and collision centrality. [Preview Abstract] |
Saturday, October 21, 2017 11:18AM - 11:30AM |
K6.00005: Beautiful Measurements: Heavy-Flavor Electrons in ALICE at the LHC Erin Gauger The quark gluon plasma (QGP) is a state of matter formed in high-energy, heavy-ion collisions in which quarks and gluons are momentarily deconfined in a strongly interacting medium. To study this state of matter, which is too short-lived to be measured directly, one can study the behavior of different flavors of quarks in Pb-Pb collisions. Heavy-flavor quarks (charm and beauty) are particularly useful as a probe, as they are created at the beginning of heavy-ion collisions and must travel through the QGP medium before their decay particles reach detectors. In this talk, I will discuss recent heavy-flavor measurements in A Large Ion Collider Experiment (ALICE) at the Large Hadron Collider (LHC). In particular, I will focus on nuclear modification factor measurements of heavy-flavor and beauty-decay electrons in Pb-Pb collisions. Though semi-leptonic decay channels of heavy-flavor hadrons have a high branching ratio, these measurements can be challenging due to background sources of electrons. I will end my talk with discussion of new analysis techniques being used to remedy this problem and improve beauty-decay electron signals. [Preview Abstract] |
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