Bulletin of the American Physical Society
2019 Fall Meeting of the APS Division of Nuclear Physics
Volume 64, Number 12
Monday–Thursday, October 14–17, 2019; Crystal City, Virginia
Session GN: Nuclear Structure II |
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Chair: Elizabeth McCutchan, Brookhaven National Laboratory Room: Salon K |
Tuesday, October 15, 2019 2:00PM - 2:12PM |
GN.00001: Study of nuclear structure of 32Mg to probe the island of inversion Yongchi Xiao, Ben Crider, Sean Liddick, Kaite Childers, Partha Chowdhury, Edward Lamere, Rebecca Lewis, Brenden Longfellow, Stephanie Lyons, Shree Neupane, David Perez-Loureiro, Timilehin Ogunbeku, Chris Prokop, Andrea Richard, Umesh Silwal, Durga Siwakot, Dylan Smith, Mallory Smith At the limits of the nuclear landscape, nuclei may exhibit different ground state properties as the result of shell evolution. At the center of the N$=$20 island of inversion in Mg, a recently identified shape coexistent excited 0$+$ state was found with potentially large mixing with the ground state. Exploring the nature of these 0$+$ states, and the states that are built on top of them, is important for understanding shape coexistence and configuration mixing in this region. An experiment was performed at NSCL to study Mg via the decay of Na and Na ($\beta $n) which utilized a CeBrimplantation-decay detector along with ancillary detection arrays for energy and timing characterization. Preliminary results and a tentative level scheme produced from this work will be presented. [Preview Abstract] |
(Author Not Attending)
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GN.00002: Ground-state magnetic-dipole moment of $^{37}$Ca* K. Minamisono, A. J. Miller, B. A. Brown, J. Watkins, A. Klose, D. Garand, C. Sumithrarachchi, J. D. Holt, A. Teigelh$\ddot{\rm o}$fer, J. D. Lantis, S. V. Pineda, Y. Liu, B. Maa$\beta$, W. N$\ddot{\rm o}$rtersh$\ddot{\rm a}$user, D. M. Rossi, F. Sommer, A. Schwenk The ground-state magnetic-dipole moment of $^{37}$Ca, which has one neutron add to $^{36}$Ca with the neutron number $N$ = 16, was determined to probe the closed-shell nature of the $^{36}$Ca nucleus. The hyperfine spectrum of the D2 transition in $^{37}$Ca ion was measured using collinear laser spectroscopy technique at BECOLA at NSCL/MSU. The resulting magnetic moment was compared with the shell model and in-medium similarity renormalization group calculations. The details of experiment and results will be discussed. [Preview Abstract] |
Tuesday, October 15, 2019 2:24PM - 2:36PM |
GN.00003: Cross-shell configurations in $^{38}$Cl structure and the quest for a new shell model interaction. Rebeka Sultana Lubna, Konstantinos Kravvaris, Samuel Tabor, Vandana Tripathi, Alexander Volya, Elizabeth Rubino, James Allmond, Brittany Abromeit, Lagy Baby, Thaxter Hensley $^{38}$Cl with Z = 17 and N = 21 has long been recognized as providing a window into the interactions between $\pi 0d_{3/2}$ and $\nu f_{7/2}$ nucleons. The availability of a $^{14}$C beam to occur a fusion evaporation reaction in conjunction with the $\gamma$-detector array at the John. D. Fox laboratory has allowed further exploration of the higher-spin structure of $^{38}$Cl to elucidate the role of excitations across the N = 20 shell gap. Comparison with microscopic structure models has proved very fruitful in the past in interpreting level schemes, but were limited by the need to adjust the N = 20 shell gap for cross-shell excitations for different nuclei. Therefore, we developed a microscopic effective interaction based on fitting the shell model cross-shell interaction matrix elements over a wide range of particle-hole states in nuclei across the $sd$ shell and beyond. The main focus was to tune the monopole terms across the shell gaps, N = 8 and N =20. The valence space of the new FSU interaction comprises the $spsdpf$ model space, compatible to the normal and intruder states of the $sd$ shell isotopes. The shell model calculations using FSU interaction have been performed in this work to better understand the structure of $^{38}$Cl and some nearby even A Cl isotopes. [Preview Abstract] |
Tuesday, October 15, 2019 2:36PM - 2:48PM |
GN.00004: Probing Spin-Isospin Excitations in Proton-Rich Nuclei via the (p,n) Reaction Jaclyn Schmitt, Remco Zegers, Daniel Bazin, Alex Carls, Alyssa Davis, Miles DeNudt, Bingshui Gao, Charles Hultquist, Shumpei Noji, Jorge Pereira, Rachel Titus, Juan Zamora Tracking the evolution of nuclear properties away from stability serves as a valuable test for nuclear models. The proton-rich nuclei $^{12}$O and $^{11}$N were studied via the (p,n) reaction in inverse kinematics using $^{12}$N and $^{11}$C beams, respectively, at 100~MeV/A at the National Superconducting Cyclotron Laboratory (NSCL). The differential cross sections can be calculated from the energy and angle of the recoil neutrons, measured by the Low Energy Neutron Detector Array (LENDA). Then the Gamow-Teller transition strength can be extracted from the cross section and compared to predictions of theoretical models. In the case of $^{12}$O, the resulting structure information can also be compared to the mirror nucleus $^{12}$Be to explore possible mirror symmetry breaking for extreme proton-to-neutron ratios. This experiment will also establish the (p,n) reaction as a probe to extract Gamow-Teller strengths from proton-rich nuclei, which can be used to study isotopes up to the $^{100}$Sn region during the FRIB era. Progress of the analysis for this experiment will be presented. [Preview Abstract] |
Tuesday, October 15, 2019 2:48PM - 3:00PM |
GN.00005: Inverse-kinematics proton scattering from $^{42,44}$S, $^{41,43}$P L. A. Riley, S. D. Gregory, E. B. Haldeman, B. R. Klybor, M. A. Liggett, L. M. Skiles, P.D. Cottle, K. W. Kemper, A. Volya, D. Bazin, J. Belarge, P. C. Bender, B. A. Brown, B. Elman, A. Gade, S. Lipschutz, B. Longfellow, E. Lunderberg, T. Mijatovic, J. Pereira, R. Titus, D. Weisshaar, J. C. Zamora, R. G. T. Zegers Excited states of $^{42,44}$S and $^{41,43}$P have been studied via inverse-kinematics proton scattering from a liquid hydrogen target, using the GRETINA $\gamma$-ray tracking array. Proton-scattering deformation lengths of the $2^+_1$ excitations in $^{42,44}$S have been combined with electromagnetic deformation lengths to yield the ratio of neutron-to-proton matrix elements $M_n/M_p$. The status of the $N=28$ major shell gap approaching $^{42}$Si is discussed in light of the systematic behavior of $M_n/M_p$ in even-even nuclei, and the $^{41,43}$P$(p,p')$ results are used to compare the SDPF-U and SDPF-MU shell-model interactions. [Preview Abstract] |
Tuesday, October 15, 2019 3:00PM - 3:12PM |
GN.00006: (CEU) Study of excited neutron-rich $^{44,45}$Ca isotopes populated through fusion-evaporation Andrew MacGregor, Peter Bender The search for high-spin states with a clear n-particle-hole configurations are key to unraveling the mysteries of evolving nuclear structure. Such states are often high spin in nature and naturally populated via the fusion-evaporation reaction mechanism. Through careful gamma spectroscopy, these states can be unambiguously identified and used as rigorous tests to state of the art nuclear theory. A recent experiment at the John D. Fox superconducting Laboratory at FSU was preformed to examine such states. Here, a $^{14}$C beam was impinged on a $^{36}$S target at 34-Mev. The experimental setup included an array of HPGe detectors as well as a Si telescope for identification of evaporated charged particles. In this work, the alpha evaporation channel will be presented and the detailed gamma-ray spectroscopy results for $^{44,45}$Ca will be presented. Aspects of the experimental approach and data analysis will be presented. Final results will be discussed and compared to recent shell model calculations. [Preview Abstract] |
Tuesday, October 15, 2019 3:12PM - 3:24PM |
GN.00007: High-spin States and Cross-shell Excitations in \textsuperscript{46}Ca John Ash, Hironori Iwasaki, Tea Mijatovic, Robert Elder, Mara Grinder, Yutaka Utsuno, Ching-Yen Wu, Jack Henderson, Dirk Weisshaar, Alexandra Gade, Mark-Christoph Spieker, Brandon Elman, Brenden Longfellow, Daniel Rhodes Investigation into the evolution of shell structure often necessitates probing far from stability, near the neutron dripline. However, in the case of the calcium isotopes, previously inaccessible high-spin states in stable nuclei offer a new direction to examine structure near doubly-magic \textsuperscript{48}Ca. These state energies can inform shell model interactions and improve our understanding of cross-shell excitations in the region. To achieve this end, previously unknown states in \textsuperscript{46}Ca were populated using the first fusion evaporation reaction at the reaccelerated beam facility (ReA3) of the National Superconducting Cyclotron Laboratory. Using particle and gamma coincidence techniques, several new transitions were observed and compared to large-scale shell model calculations. [Preview Abstract] |
Tuesday, October 15, 2019 3:24PM - 3:36PM |
GN.00008: Electroweak transitions in intermediate mass nuclei Grigor Sargsyan, Kristina Launey, Tomas Dytrych, Jerry Draayer We present beta decay rates and B(E2) strengths calculated using the \emph{ab initio} symmetry-adapted no-core shell model (SA-NCSM). The SA-NCSM utilizes emergent symmetries in nuclei in order to reduce the dimensionality of the model space. This, in turn, allows one to reproduce the low-energy nuclear dynamics with only a small fraction of the model space, and hence making solutions to heavier nuclei feasible. The symmetry-adapted basis of the SA-NCSM is well suited for describing electromagnetic and beta-decay transitions enabling us to use the full capability of the model and perform calculations for \emph{sd}-shell as well as \emph{pf}-shell nuclei. This work discusses the reproduction of B(E2) strengths in intermediate-mass nuclei from first principles and without effective charges. It also focuses on a study of the $g_A$ quenching problem for bare interactions (no renormalization involved) and with collective correlations that are well described within the model, as well as on a study of $^{48}$Ca and $^{48}$Ti of interest to neutrinoless double beta decays. [Preview Abstract] |
Tuesday, October 15, 2019 3:36PM - 3:48PM |
GN.00009: Detailed spectroscopy following the $^{14}$C on $^{36}$S fusion-evaporation reaction Peter Bender, Peter DeRosa, Daniel Foulds-Holt, Andrew MacGregor, Samual Tabor, Vandana Tripathi, Rebeka Lubna, Elizabeth Rubino, James Allmond High-spin state in neutron-rich Sc isotopes were produced using the ${^36}$S($^{14}$C,$pnn\gamma$) reaction at 34-MeV at Florida State University(FSU). The FSU $\gamma$-array, which is a mix of both signal crystal and clover-style HPGe detectors, was used to detect the prompt $\gamma$-radiation. A silicon telescope placed at $0^\circ$ was used to detect and clearly identify charged particles released from the reaction. The level scheme for $^{47}$Sc has been extend, approaching the neutron separation energy. Natural alignment following the reaction has allowed angular distributions to be extracted. States with clear particle-hole configurations have been identified from proton$-\gamma-\gamma$ coincidences. The experimental results will be presented and discussed in light of recent shell-model calculations. [Preview Abstract] |
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