Wed·Nov 29, 2017Wednesday·November 29, 2017

1. 01*

   Structures in the nuclear electric-dipole spectrum

   P. Papakonstantinou🇰🇷

   I undertake an anatomy of the nuclear electric-dipole spectrum and discuss selected observations. First, using data and calculations on 208Pb as a representative case, I identify five conspicuous structures in the spectra of heavy nuclei: (1) the giant dipole resonance (GDR), (2) the dipole compression mode, (3) the isoscalar low-energy dipole mode (IS-LED),(4) the isoscalar mode in the region of the GDR, and (5) a concentration of "pygmy" dipole strength (PDS) between the latter two. Next, compiling the data from Texas A&M I show that the energy of (4) follows roughly a A^{-1/6} dependence on the mass number. Finally, I summarize recent theoretical studies on the PDS in exotic nuclei, which suggest a strong influence of shell effects and loose binding.

   ↳ nucl-thnucl-exIn Proceedings of the International Sympo…·0 citations
2. 02*

   Spin-isospin excitation of ${}^3$He with three-proton final state

   Souichi Ishikawa

   Spin-isospin excitation of ${}^3$He nucleus by proton-induced charge-exchange reaction, ${}^3\mathrm{He}(p,n)ppp$, at forward neutron scattering angle is studied in a plane wave impulse approximation (PWIA). In PWIA, cross sections of the reaction is written in terms of proton-neutron scattering amplitudes and response functions of the transition from ${}^3$He to three-proton state by spin-isospin transition operators. The response functions are calculated with realistic nucleon-nucleon potential models using a Faddeev three-body method. Calculated cross sections agree with available experimental data in substance. Possible effects arising from the uncertainty of proton-neutron amplitudes and three-nucleon interactions in three-proton system are examined.

   ↳ nucl-thnucl-exPTEP(2018)·3 citations
3. 03*

   Dilepton production and resonance properties within a new hadronic transport approach in the context of the GSI-HADES experimental data

   Jan Staudenmaier🇩🇪 · Janus Weil🇩🇪 · Vinzent Steinberg🇩🇪 · Stephan Endres🇩🇪 · Hannah Petersen🇩🇪

   The dilepton emission in heavy-ion reactions at low beam energies is examined within a hadronic transport approach. In this article the production of electron-positron pairs from a new approach named SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced. The dilepton emission is consistently taken into account below the hadronic threshold. The calculations are systematically confronted with HADES data in the kinetic energy range of $1-3.5A$ GeV for elementary, proton-nucleus and nucleus-nucleus reactions. The present approach employing a resonance treatment based on vacuum properties is validated by an excellent agreement with experimental data up to system sizes of carbon-carbon collisions. After establishing this well-understood baseline in elementary and small systems, the significance of medium effects is investigated with a coarse-graining approach based on the same hadronic evolution. The effect of explicit in-medium modifications to the vector meson spectral functions is important for dilepton invariant mass spectra in ArKCl and larger systems, even though the transport approach with vacuum properties reveals similar features due the coupling to baryonic resonance and the intrinsically included collisional broadening. This article provides a comprehensive comparison of our calculations with published dielectron results from the HADES collaboration. In addition, the emission of dileptons is predicted in gold-gold and pion-beam experiments for which results are expected soon.

   ↳ nucl-thhep-phnucl-exPRC(2018)·62 citations
4. 04*

   Contamination Control and Assay Results for the Majorana Demonstrator Ultra Clean Components

   C.D. Christofferson🇺🇸 · N. Abgrall🇺🇸 · S.I. Alvis🇺🇸 · I.J. Arnquist🇺🇸 · F.T. Avignone III🇺🇸 · A.S. Barabash🇷🇺 · C.J. Barton🇺🇸 · F.E. Bertrand🇺🇸 · T. Bode🇩🇪 · A.W. Bradley🇺🇸 · V. Brudanin🇷🇺 · M. Busch🇺🇸 and 58 other authors

   The MAJORANA DEMONSTRATOR is a neutrinoless double beta decay experiment utilizing enriched Ge-76 detectors in 2 separate modules inside of a common solid shield at the Sanford Underground Research Facility. The DEMONSTRATOR has utilized world leading assay sensitivities to develop clean materials and processes for producing ultra-pure copper and plastic components. This experiment is now operating, and initial data provide new insights into the success of cleaning and processing. Post production copper assays after the completion of Module 1 showed an increase in U and Th contamination in finished parts compared to starting bulk material. A revised cleaning method and additional round of surface contamination studies prior to Module 2 construction have provided evidence that more rigorous process control can reduce surface contamination. This article describes the assay results and discuss further studies to take advantage of assay capabilities for the purpose of maintaining ultra clean fabrication and process design.

   ↳ physics.ins-detnucl-exAIP Conf.Proc.(2018)·6 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.