Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session NG: Nuclear Structure: Light Nuclei II |
Hide Abstracts |
Chair: Christopher Lister, Argonne National Laboratory Room: Peralta |
Saturday, November 6, 2010 10:30AM - 10:42AM |
NG.00001: Collectivity of Neutron-rich Silicon Isotopes A. Ratkiewicz, A. Gade, T. Glasmacher, T. Baugher, D. Bazin, S. Barthelemy, A. Brown, C. Campbell, G. Grinyer, S. McDaniel, R. Meharchand, K. Meierbachtol, A. Signoracci, A. Spyrou, R. Stroberg, P. Voss, K. Walsh, D. Weisshaar, R. Winkler, P. Cottle, K. Kemper, A. Uribarri, D. Miller, E. Rodal, Y. Utsuno The determination of the electric quadrupole transition strength between the ground state and first excited state with spin-party of J$^{\pi}$=2$^{+}$ (the B(E2) value) in an even-even nucleus provides a measurement of the low-lying quadrupole collectivity. The B(E2) values for $^{34,36,38,40,42}$Si were measured via relativistic Coulomb excitation at NSCL. The secondary beams were produced by the fragmentation of $^{48}$Ca primary beam and guided onto a high-Z target. De-excitation gamma rays indicating the inelastic process were detected at the target with the scintillator array CAESAR in coincidence with scattered projectiles tracked on an event-by-event basis in the S800 spectrograph. The results comprise the first measurements of the quadrupole collectivity of $^{40}$Si and $^{42}$Si. The measured B(E2) values are compared to large-scale shell model calculations and provide insight into the evolution of shell structure and deformation in this region. [Preview Abstract] |
Saturday, November 6, 2010 10:42AM - 10:54AM |
NG.00002: Structure of $^{32}$P at high spins R. Chakrabarti, S. Mukhopadhyay, R. Bhattacherjee, S.S. Ghugre, A.K. Sinha, A. Dhal, L. Chaturvedi, M. Kumar Raju, N. Madhavan, R.P. Singh, S. Muralithar, B.K. Yogi, U. Garg High spin states in $^{32}$P were populated for the first time using heavy ion fusion reaction $^{18}$O($^{16}$O, 1p1n)$^{32}$P. De-exciting $\gamma$ rays were detected with the multi-clover (18 clovers) Indian National Gamma Array. The observed excitation energies for the low-lying negative and positive parity states were reproducible within the truncated sd-pf shell model calculations without resorting to the lowering of the sd-pf shell gap as done for nuclei in this mass region [1]. Lifetime and spin-parity measurements have been undertaken and the experimental branching ratios were obtained. Comparison of the above observed values with the theoretical predictions are expected to yield valuable insight into the role of the intruder configurations and an understanding of the transition in shell structure as one approaches the island of inversion.\\[4pt] [1] P. C. Bender et al., Phys. Rev. C 80, 014302 (2009). [Preview Abstract] |
Saturday, November 6, 2010 10:54AM - 11:06AM |
NG.00003: Gamow-Teller transitions from unstable $^{34}$P to $^{34}$Si via the ($^{7}$Li,$^{7}$Be+$\gamma )$ reaction in inverse kinematics R.G.T. Zegers, R. Meharchand, Y. Shimbara, Sam M. Austin, D. Bazin, B.A. Brown, C. Aa. Diget, A. Gade, C.J. Guess, M. Hausmann, G.W. Hitt, D. Weisshaar, M. King, D. Miller, J. Yurkon, A. Signoracci, K. Starosta, C. Tur, C. Vaman, P. Voss, M.E. Howard, S. Noji Although charge-exchange reactions at intermediate energies with a variety of probes on stable nuclei have long been the preferred tool to extract Gamow-Teller strengths beyond the Q-value window available for $\beta$-decay, the implementation of such reactions for rare isotopes has proven to be an experimental challenge. Here, we report on the first successful extraction of a $\beta $+ Gamow-Teller strength distribution from a radioactive isotope in an intermediate-energy charge-exchange experiment in inverse kinematics. The ($^{7}$Li,$^{7}$Be+$\gamma )$ reaction at 100 AMeV was used to measure Gamow-Teller transition strengths from $^{34}$P to states in $^{34}$Si. The results show that little mixing occurs between sd and pf shell configurations for the low-lying 0$^{+}$ and 2$^{+}$ states even though $^{34}$Si neighbors the island of inversion and low-lying intruder states exist. [Preview Abstract] |
Saturday, November 6, 2010 11:06AM - 11:18AM |
NG.00004: ABSTRACT WITHDRAWN |
Saturday, November 6, 2010 11:18AM - 11:30AM |
NG.00005: Transition Quadrupole Collectivity of Ar and Cl Isotopes Near N = 28 R. Winkler, A. Gade, B.A. Brown, T. Glasmacher, T.R. Baugher, D. Bazin, G.F. Grinyer, S. McDaniel, R. Meharchand, A. Ratkiewicz, R. Stroberg, K. Walsh, D. Weisshaar, L.A. Riley Measurements of the reduced quadrupole transition strengths, B(E2; 0$^{+}$ $\to $ 2$^{+})$ of even-even nuclei guide our understanding of the onset collectivity with the addition of valence nucleons beyond the known shell structure of the atomic nucleus. The study of the quadrupole collectivity of neutron-rich $^{47,48}$Ar and $^{45,46}$Cl via relativistic Coulomb excitation was performed using a cocktail of exotic beams produced by the coupled cyclotron facility at NSCL. Particle tracking and identification was achieved on an event-by-event basis using the S800 high-resolution spectrograph. Gamma rays emitted at the reaction target position in coincidence with the detection of scattered particles were observed with the segmented high-purity Germanium array SeGA, a vital tool for the Doppler reconstruction of each observed event. Results from the present work provide insight into the persistence of the $N = 28$ shell closure and will be discussed in the framework of the shell model utilizing modern effective interactions in the \textit{sdpf} valence space. This work is supported by the National Science Foundation under Grants No. PHY-0606007 and PHY-0758099. [Preview Abstract] |
Saturday, November 6, 2010 11:30AM - 11:42AM |
NG.00006: Spectroscopic Factors from the Single Neutron Pickup $^{64}$Zn($\vec{\mathrm{d}}$,t) Kyle Leach, P.E. Garrett, G.A. Demand, P. Finlay, K.L. Green, A.A. Phillips, E.T. Rand, C.S. Sumithrarachchi, C.E. Svensson, S. Triambak, J. Wong, I.S. Towner, G.C. Ball, T. Faestermann, R. Kr\"ucken, R. Hertenberger, H.-F. Wirth A great deal of attention has recently been paid towards high-precision superallowed $\beta$-decay ${\cal F}t$ values. With the availability of extremely high-precision $(<0.1\%)$ experimental data, precision on the individual ${\cal F}t$ values are now dominated by the $\sim1\%$ theoretical corrections. This limitation is most evident in heavier superallowed nuclei (e.g. $^{62}$Ga) where the isospin-symmetry-breaking (ISB) correction calculations become more difficult due to the truncated model space. Experimental spectroscopic factors for these nuclei are important for the identification of the relevant orbitals that should be included in the model space of the calculations. Motivated by this need, the single-nucleon transfer reaction $^{64}$Zn$(\vec{\mathrm{d}}$,t)$^{63}$Zn was conducted at the Maier-Leibnitz-Laboratory (MLL) of TUM/LMU in Munich, Germany, using a 22~MeV polarized deuteron beam from the tandem Van de Graaff accelerator and the TUM/LMU Q3D magnetic spectrograph, with angular distributions from $10^{\circ}$ to $60^{\circ}$. Results from this experiment will be presented and implications for calculations of ISB corrections in the superallowed $\beta^+$ decay of $^{62}$Ga will be discussed. [Preview Abstract] |
Saturday, November 6, 2010 11:42AM - 11:54AM |
NG.00007: New band structures in neutron-rich odd-$A$ Ge isotopes C.J. Chiara, N. Sharp, I. Stefanescu, J.R. Stone, W.B. Walters, M.P. Carpenter, G. G\"{u}rdal, C.R. Hoffman, R.V.F. Janssens, B.P. Kay, F.G. Kondev, T. Lauritsen, C.J. Lister, E.A. McCutchan, D. Seweryniak, S. Zhu, R. Broda, B. Fornal, W. Kr\'{o}las, T. Paw\l at, J. Wrzesi\'{n}ski, N.J. Stone Neutron-rich Ge isotopes were studied in a campaign of experiments with the Gammasphere Ge-detector array at ANL. Beams of $^{76}$Ge were incident upon thick $^{238}$U, $^{208}$Pb, and $^{198}$Pt targets in deep-inelastic reactions, populating excited states up to moderate spins. No previous high-spin work has been done on $^{75,77}$Ge, with most existing data coming from $\beta$ decay, neutron capture, or transfer reactions. The level schemes for both nuclides have been extended, including the observation of strongly-coupled band structures. In some cases, spin and parity assignments are strengthened by angular-correlation measurements. These isotopes straddle the neutrinoless double $\beta$-decay candidate $^{76}$Ge; additional data on the levels in these systems can provide tests of shell-model calculations for nuclei in this region involving the $p_{3/2}p_{1/2}f_{5/2}g_{9/2}$ proton and neutron subspace. [Preview Abstract] |
Saturday, November 6, 2010 11:54AM - 12:06PM |
NG.00008: Evolution of Shape in the Nucleus $^{71}$Se S.M. Fischer, C.J. Lister Nuclei near $N=Z$ with $A$ around 70-80 exhibit a variety of shapes and deformations, as well as shape coexistence within a single nucleus. Shapes are often inferred from the magnitudes and irregularities of moments of inertia of the observed rotational bands [1]. In some cases, the deformation of one or more low- lying states has been measured [2]. The $A\sim70$ selenium nuclei are predicted to be oblate at low excitation, but quickly become prolate as the excitation energy and angular momentum increase. Excited states in $^{71}$Se were produced in the $4pn$ channel of the $^{36}$Ar + $^{40}$Ca reaction at 145 MeV. Both signatures of the $g_{9/2}$ band are observed, and at least three transitions between the two signatures are intense enough such that mixing ratios can be extracted. These mixing ratios allow us to track and quantify the evolution from oblate to prolate shape of this nucleus. \\[4pt] [1] S.M. Fischer et al., Phys. Rev. Lett. 84, 4064 (2000). \newline [2] A. Obertelli et al., Phys. Rev. C 80, 031304(R) (2009). [Preview Abstract] |
Saturday, November 6, 2010 12:06PM - 12:18PM |
NG.00009: Dipole Excitations of 76 Se in the Energy Range 5-9 MeV Philip Goddard, V. Werner, M. Smith, N. Cooper, D. Savran, N. Pietralla, C. Romig, E. Kwan, J.H. Kelley, R. Raut, G. Rusev, A.P. Tonchev, W. Tornow, S.W. Yates, A. Chakraborty, B. Crider, E. Peters The Pygmy Dipole Resonance, which is found on the low-energy tail of the GDR has been studied via scattering of real photons in $^{76}$Se. After an initial scan of the 5-9 MeV exitation energy region with unpolarized photons, within this work parities of dipole excited states were unambiguously determined via polarimetry after excitation with polarized photons from the free electron laser at HIGS/TUNL. First results will be presented, which will serve as future tests for the structure of this $0\nu2\beta$-relevant isotope. [Preview Abstract] |
Saturday, November 6, 2010 12:18PM - 12:30PM |
NG.00010: Infinite-cutoff renormalization of the chiral NN potential up to N3LO Ruprecht Machleidt, Christopher Zeoli Naively, the ``best'' method of renormalization is the one where the momentum cutoff is taken to infinity while maintaining stable results due to a cutoff-dependent adjustment of counter terms. We have applied this renormalization method in the calculation of phase-shifts for nucleon-nucleon (NN) scattering using chiral NN potentials up to next-to-next-to-next-to-leading order (N3LO). For lower partial waves, we find that there is either no convergence with increasing order or, if convergence occurs, the results do not converge to the empirical values. For higher partial waves, we always observe convergence to the empirical phase shifts (except for the 3G5 state). Furthermore, no matter what the order is, one can use only one or no counter term per partial wave, creating a rather erratic scheme of power counting that does not allow for a systematic order-by-order improvement of the predictions. The conclusion is that infinite-cutoff renormalization is inappropriate for chiral NN potentials, which should not come as a surprise, since the chiral effective field theory these potentials are based upon is designed for momenta below the chiral-symmetry breaking scale of about 1 GeV. This value for the hard scale should be perceived as a reasonable upper limit for the cutoff. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700