Bulletin of the American Physical Society
15th Annual Meeting of the Northwest Section of the APS
Volume 59, Number 6
Thursday–Saturday, May 1–3, 2014; Seattle, Washington
Session G3: Nuclear Physics |
Hide Abstracts |
Chair: Sonia Bacca, TRIUMF Room: Alder Commons 105 |
Saturday, May 3, 2014 1:30PM - 2:00PM |
G3.00001: Atomic weights are not constants of Nature! Reading the stories told by the isotopes Invited Speaker: Michael Wieser The observation of two stable isotopes of neon by J. J. Thompson in 1912 was the first chapter in what would become arguably one of the most significant breakthroughs in Science. Thompson's ingenious yet simple device employed electric and magnetic fields to reveal the existence of isotopes and this original design is the basis for modern instrumentation used in the measurement of isotope abundances. The mass spectrometer quickly became an important tool in the determination of the atomic weights of the elements, quantities that were thought at the time to be Constants of Nature. However, with increasing instrumental precision came the remarkable discovery that not all occurrences of an element had the same atomic weight values because of differences in isotopic composition. Researchers saw this discovery as a remarkable opportunity to use variations in isotopic composition to learn intimate information about physical, nuclear, and biological processes that may affect a particular element. Over the past 100 years technical and instrumental advances have enabled investigations supported by isotope abundance data to have an impact on our scientific understanding of our world and our health and well being in this world. In this talk, I will review the major discoveries that led to the development of modern isotope amount ratio measurement techniques and illustrate the insights made possible by these methods. I will highlight the knowledge we have gained as a result of reading the stories told by the isotopes. [Preview Abstract] |
Saturday, May 3, 2014 2:00PM - 2:12PM |
G3.00002: Nonperturbative renormalization of the chiral nucleon-nucleon interaction up to next-to-next-to-leading order Ehab Marji, Amrah Canul, Quinn MacPherson, Rebecca Winzer, Christopher Zeoli, David Entem, Ruprecht Machleidt We study the nonperturbative renormalization of the nucleon-nucleon $(NN)$ interaction at next to-leading order (NLO) and next-to-next-to-leading order (NNLO) of chiral effective field theory. A systematic variation of the cutoff parameter is performed for values below the chiral symmetry breaking scale of about 1 GeV. The accuracy of the predictions is determined by calculating the $\chi^2$ for the reproduction of the $NN$ data for energy intervals below pion-production threshold. At $NLO$, $NN$ data are described well up to about 100 MeV laboratory energy and, at NNLO, up to about 200 MeV|with, essentially, cutoff independence for cutoffs between about 450 and 850 MeV. [Preview Abstract] |
Saturday, May 3, 2014 2:12PM - 2:24PM |
G3.00003: Understanding The Proton Radius Puzzle: ``Nuclear Polarizability Corrections in Muonic Deuterium" Oscar Hernandez, Chen Ji, Sonia Bacca, Nir Nevo Dinur, Nir Barnea In 2010 the accuracy of the rms proton radius was improved ten-fold by new spectroscopic measurements of the Lamb shift in muonic hydrogen. However, this new value differed by $7 \sigma$ from what was previously determined in ordinary hydrogen. This large discrepancy was coined the ``proton radius puzzle" and challenges our understanding of physics based on the standard model. New high-precision measurements on various muonic atoms are planned at PSI to study whether this discrepancy persists or varies with mass and charge numbers. The accuracy of the nuclear charge radii determination from their data is limited by the uncertainty in the nuclear polarizability corrections. For $\mu D$, these nuclear corrections have been most recently calculated by Pachucki with the AV18 nuclear potential. In this contribution I would like to show how we complement Pachucki's pioneering work by performing ab-initio calculations in $\mu D$ with state-of-the-art nuclear potentials from chiral effective field theory. We take into account multipole corrections, Coulomb, relativistic and finite-nucleon-size corrections. Furthermore, performing a systematic study in chiral effective field theory will allow us to better assess the theoretical error associated to the polarizability. [Preview Abstract] |
Saturday, May 3, 2014 2:24PM - 2:36PM |
G3.00004: Alternative Similarity Renormalization Group Generators in Nuclear Structure Calculations Nuiok Dicaire, Conor Omand, Petr Navr\'atil The Similarity Renormalization Group (SRG) has been successfully applied to soften interactions for \textit{ab initio} nuclear calculations. In almost all practical applications in nuclear physics, an SRG generator with the kinetic energy operator was used. With this choice, a fast convergence of many-body calculations can be achieved, but at the same time substantial three-body interactions are induced even if one starts from purely two-nucleon (NN) Hamiltonian. Three-nucleon (3N) interactions can be handled by modern many-body methods. However, it has been observed that when including initial chiral 3N forces in the Hamiltonian, the SRG transformations induce non-negligible four-nucleon interactions that cannot be currently included in calculations for technical reasons. Consequently, it is essential to investigate alternative SRG generators that might suppress the induction of many-body forces while at the same time might preserve the good convergence. We present different alternative generators with operators of block structure in the harmonic oscillator basis. In the no-core shell model calculations for $^{3}$H, $^{4}$He and $^{6}$Li with chiral NN force, we demonstrate that they appear quite promising. [Preview Abstract] |
Saturday, May 3, 2014 2:36PM - 2:48PM |
G3.00005: Towards Ab-Initio Calculations of Electromagnetic Reactions in Medium-Mass Nuclei Mirko Miorelli, Sonia Bacca, Nir Barnea, Gaute Hagen, Giuseppina Orlandini, Thomas Papenbrock Electromagnetic reactions with nuclei are important in many fields of physics ranging from nuclear physics to astrophysics. The response of a nucleus to the interaction of an external electromagnetic probe is a crucial observable to test our understanding of nuclear dynamics. Until very recently, most of the ab-initio calculations of such reactions where the nucleus is broken in several pieces, were restricted to very light nuclei ($A\le 7$). By merging coupled-cluster theory and the Lorentz integral transform method one can extend the ab-initio study of electromagnetic break-up reactions to the region of medium-mass nuclei . We first benchmark the new method in \textsuperscript{4}He and then address the photo-disintegration of \textsuperscript{16}O. We then move to \textsuperscript{40}Ca and \textsuperscript{48}Ca, and investigate the electric dipole polarizability. Preliminary results indicate a correlation between the polarizability and the neutron-skin radius of \textsuperscript{48}Ca. This latter is attracting a lot of attention in nuclear physics and experiments to measure both the polarizability and the neutron-skin radius are planned/ongoing at RCNP and JLAB respectively. [Preview Abstract] |
Saturday, May 3, 2014 2:48PM - 3:00PM |
G3.00006: Nuclear thermodynamics from chiral low-momentum interactions Jeremy Holt, Corbinian Wellenhofer, Norbert Kaiser, Wolfram Weise The thermodynamical equation of state of asymmetric nuclear matter is an important input for simulations of core-collapse supernovae. In the present work we take advantage of recent improvements in nuclear force models based on chiral effective field theory to construct an equation of state of nuclear matter at finite temperature. Nuclear two-body forces fit to elastic nucleon-nucleon scattering phase shifts and three-body forces fit to the binding energy and lifetime of the triton form the microscopic basis for our perturbative calculations. Bulk properties of symmetric nuclear matter at zero temperature are used to benchmark our many-body methods and nuclear force models, and uncertainty estimates on the equation of state are obtained by varying the resolution scale at which nuclear dynamics are resolved. [Preview Abstract] |
Saturday, May 3, 2014 3:00PM - 3:12PM |
G3.00007: A Microscopic Approach to Neutron-Rich Matter Larz White, Francesca Sammarruca Our group is concerned with the properties of the nuclear force in the medium, particularly in the presence of unequal densities of protons and neutrons. The approach we take is ``ab initio,'' in the sense that realistic nucleon-nucleon forces are used as the input of many-body calculations, without phenomenological contributions. Intense computation is an essential element in microscopic nuclear physics. Our most recent effort consists of the solution of a large number of coupled integral equations describing scattering of nucleons in nuclear matter. Our solution method does not rely on partial-wave decomposition of the scattering amplitude and removes the need for standard approximations typically applied when including the Pauli blocking mechanism. [Preview Abstract] |
Saturday, May 3, 2014 3:12PM - 3:24PM |
G3.00008: The Cooling of the Cassiopeia A Neutron Star as a Probe of the Nuclear Symmetry Energy and Nuclear Pasta Kyleah Murphy, William Newton, Josh Hooker, Bao-An Li X-ray observations of the neutron star in the Cas A supernova remnant over the past decade suggest the star is undergoing a rapid drop in surface temperature of $\approx $ 2$-$5.5{\%}. One explanation suggests the rapid cooling is triggered by the onset of neutron superfluidity in the core of the star, causing enhanced neutrino emission from neutron Cooper pair breaking and formation (PBF). Using consistent neutron star crust and core equations of state (EOSs) and compositions, we explore the sensitivity of this interpretation to the density dependence of the symmetry energy $L$ of the EOS used, and to the presence of enhanced neutrino cooling in the bubble phases of crustal ``nuclear pasta.'' Modeling cooling over a conservative range of neutron star masses and envelope compositions, we find $L\le $70 MeV, competitive with terrestrial experimental constraints and other astrophysical observations. For masses near the most likely mass of $M\ge $1.65$M\odot $, the constraint becomes more restrictive 35$\le \quad L \le $55 MeV. The inclusion of the bubble cooling processes decreases the cooling rate of the star during the PBF phase, matching the observed rate only when $L\le $45 MeV. [Preview Abstract] |
Saturday, May 3, 2014 3:24PM - 4:00PM |
G3.00009: Break
|
Saturday, May 3, 2014 4:00PM - 4:30PM |
G3.00010: Testing the Majorana Nature of the Neutrino with Germanium Detectors Invited Speaker: Jason Detwiler Among the known fundamental particles, only the neutrino could be a Majorana particle, a fermion for which the particle and antiparticle states are identical. The discovery of neutrino mass and its tininess relative to the other leptons and quarks has greatly strengthened the theoretical motivation for Majorana neutrinos. Far from being just a matter of trivia, the nature of the neutrino has deep implications for issues as far reaching as Grand Unification, the symmetries of the Standard Model, and the prevalence of matter over antimatter in the universe. I will discuss the neutrino's role in these important issues, and introduce the only known viable experimental probe of this physics: searches for neutrinoless double-beta decay. I will make the case for performing such searches using germanium semiconductor detectors, and I will discuss the status of current experiments as well as future capabilities of large-scale germanium detector arrays. [Preview Abstract] |
Saturday, May 3, 2014 4:30PM - 4:42PM |
G3.00011: Development of Low Background Components for the MAJORANA DEMONSTRATOR Ian Guinn The MAJORANA collaboration will search for neutrinoless double beta decay ($0\nu\beta\beta$) of $^{76}$Ge using high purity germanium detectors. In order to achieve a sensitivity of up to $10^{28}$ years in the $0\nu\beta\beta$ half-life, background contributions in the 4 keV region of interest around the 2039 keV Q-value of the decay will need to be below $\sim$1 count per tonne-year. Radio-purity constraints require novel designs for many components of the detector and the development of improved assay capabilities. I will present some of the design challenges and solutions of the MAJORANA experiment, with a focus on the signal cables developed at the University of Washington. [Preview Abstract] |
Saturday, May 3, 2014 4:42PM - 4:54PM |
G3.00012: Low-noise preamplifier with forward biased reset for CoGeNT and M{\sc ajorana} Jonathan Leon, Jason Detwiler, David Peterson, Hamish Robertson, Tim Van Wechel The CoGeNT and M{\sc ajorana} projects both make use of hyperpure Ge detectors that are in principle sensitive to very low-energy nuclear recoil signals, such as those produced by coherent scattering of dark matter particles or neutrinos from Ge nuclei. However, this sensitivity can only be realized if sub-keV thresholds can be achieved. We are developing a low-noise charge preamplifier which is continuously reset by the forward-biased gate-to-source junction of the input tetrode JFET. Similar to pulsed-reset preamplifiers, this design avoids the noise contributions of a feedback resistor, while providing the added benefit of continuous operation. To achieve the lowest possible threshold, it is imperative to reduce all extraneous sources of noise. We will discuss methods to measure and reduce noise contributions, focusing in particular on capacitor dissipation noise. We will also report on characterization and performance of our latest prototypes. [Preview Abstract] |
Saturday, May 3, 2014 4:54PM - 5:06PM |
G3.00013: KATRIN Progress Toward a Neutrino Mass Measurement Diana Parno The Karlsruhe Tritium Neutrino experiment (KATRIN), now under construction in Germany, will use the kinematics of tritium beta decay to probe the neutrino mass with a designed sensitivity of 0.2 eV. The KATRIN collaboration recently completed a first commissioning phase of the main spectrometer, investigating electron transmission and background processes. We will show preliminary commissioning results and summarize the current status of the experiment. [Preview Abstract] |
Saturday, May 3, 2014 5:06PM - 5:18PM |
G3.00014: The Tritium-Recoil Ion Mass Spectrometer: examining molecular effects in neutrino mass experiments Laura Bodine, Diana Parno, R.G. Hamish Robertson Detailed molecular final state calculations are required for the next generation of tritium-based neutrino mass experiments. The calculations also predict the branching ratio to the bound molecular ion $^3$HeT$^+$, which is directly measurable. The Tritium Recoil-Ion Mass Spectrometer is a time-of-flight spectrometer designed to measure molecular dissociation in tritium beta decay as a test of the calculations used in neutrino-mass analyses. We report on the status and outlook of the experiment. [Preview Abstract] |
Saturday, May 3, 2014 5:18PM - 5:30PM |
G3.00015: Weak interaction studies with laser-trapped ${^6}$He David Zumwalt, Yelena Bagdasarova, Alejandro Garcia, Ran Hong, Matt Sternberg, Derek Storm, Erik Swanson, Frederik Wauters, Kevin Bailey, Arnaud Leredde, Peter Mueller, Tom O'Connor, Xavier Flechard, Etienne Li\'enard, Oscar Naviliat-Cuncic $^6$He beta decay is an excellent case to test the nature of the weak interaction through a precise measurement of the $\beta-\overline{\nu}$ angular correlation parameter $a$. The pure Gamow-Teller decay of $^6$He should be ruled by an axial-vector interaction only, which leads to $a=-1/3$. Any deviation due to tensor coupling contributions would indicate new physics beyond the Standard Model. The high precision goal of this experiment, $\Delta{}a/a=0.1\%$, requires a large statistical sample along with small and well known systematic uncertainties. To satisfy these constraints, neutral $^6$He atoms are captured with laser light in a magneto-optical trap (MOT). $^6$He ($t_{1/2}=807$~ms) is produced on-line through the $^7$Li(d,$^3$He)$^6$He nuclear reaction by impinging a molten lithium target with an intense 18~MeV deuteron beam. Up to 10$^{10}$ $^6$He atoms per second are extracted from the target and trapped in a two stage MOT. The angular correlation parameter is obtained by detecting the $^6$Li+ recoil ions in coincidence with the beta particle. Details of the setup and first results will be presented. [Preview Abstract] |
Saturday, May 3, 2014 5:30PM - 5:42PM |
G3.00016: Corrections to Eikonal Approximation for Nuclear Scattering at Medium Energies Micah Buuck, Gerald A. Miller Interpretation of the results of future experiments at the upcoming Facility for Rare Isotope Beams (FRIB) will require accurate modeling of low energy nucleus-nucleus interactions. The Glauber theory is a very successful high-energy approach, but its accuracy suffers at some of the lower beam energies of experimental interest to FRIB. A prescription developed by Wallace that treats the Glauber approximation as the zeroth order term in an expansion around an eikonal propagator has the potential to extend the range of validity of the approximation to lower energies. Here we examine the properties of this expansion, and calculate the corrections for both simple potential scattering and for nuclear reactions involving halo nuclei. We find that the corrections improve the accuracy of Glauber theory, so that it can be used at energies as low as about 40 MeV per nucleon. [Preview Abstract] |
Saturday, May 3, 2014 5:42PM - 5:54PM |
G3.00017: Gluon Saturation Effects on Three-particle Angular Correlations in p-p and p-Pb collisions at LHC Sener Ozonder The di-hadron correlations from the CMS experiment for the high multiplicity p-p and p-Pb collisions at LHC revealed a ridge structure that looked like the ridge induced by collective flow in A+A collisions. This discovery attracted great interest since the formation of quark gluon plasma (QGP) and collective flow were not anticipated in p-p and p-Pb collisions. It has been recently shown that the p-p and p-Pb ridge can be explained by the multiladder QCD diagrams (``glasma diagrams'') that were enhanced at the saturation scale at small x. In this framework, the ridge is purely due to the interference of the wave functions of the colliding hadrons/nuclei and the saturation effects encoded in the wave functions. We calculate tri-hadron correlations from the glasma diagrams for p-p ($\sqrt{s}=$7 TeV) and p-Pb ($\sqrt{s}=$5.02 TeV) collisions at LHC. We make quantitative predictions on the associated hadron yield for the high multiplicity events, which have yet to be measured by the experimental collaborations. Our results show that the glasma diagrams give rise to the structures in the three-hadron correlation which are clearly distinguishable from the possible QGP medium effects such as collective flow, energy loss and deflection of hadrons. [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