Thu·Aug 3, 2017Thursday·August 3, 2017

1. 01*

   High-precision $Q_{EC}$-value measurement of the superallowed ${\beta }^{+}$ emitter ${}^{22}$Mg and an evaluation of the $A=22$ isobaric triplet

   M.P. Reiter🇨🇦 · K.G. Leach🇺🇸 · O. M. Drozdowski🇨🇦 · S.R. Stroberg🇨🇦 · J.D. Holt🇨🇦 · C. Andreoiu🇨🇦 · C. Babcock🇨🇦 · B. Barquest🇨🇦 · M. Brodeur🇺🇸 · A. Finlay🇨🇦 · M. Foster🇬🇧 · A.T. Gallant🇨🇦 and 13 other authors

   A direct $Q_{EC}$-value measurement of the superallowed ${\beta }^{+}$ emitter ${}^{22}$Mg was performed using TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The direct ground-state to ground-state atomic mass difference between ${}^{22}$Mg and ${}^{22}$Na was determined to be $Q_{EC}=4781.40(22)$~keV, representing the most precise single measurement of this quantity to date. In a continued push towards calculating superallowed isospin-symmetry-breaking (ISB) corrections from first principles, ab-initio shell-model calculations of the $A=22$ IMME are also presented for the first time using the valence-space in-medium similarity renormalization group formalism. With particular starting two- and three-nucleon forces, this approach demonstrates a level of agreement with the experimental data that suggests reliable ab-initio calculations of superallowed ISB corrections are now possible.

   nucl-exnucl-thPRC(2017)·13 citations
2. 02*

   Spectator-Tagged Deeply Virtual Compton Scattering on Light Nuclei

   Whitney Armstrong (1)🇺🇸 · John Arrington (1)🇺🇸 · Ian Cloët (1)🇺🇸 · Adam Freese (1)🇺🇸 · Kawtar Hafidi (1)🇺🇸 · Mohammad Hattawy (1)🇺🇸 · Seamus Riordan (1)🇺🇸 · Sereres Johnston (1)🇺🇸 · David Potteveld (1)🇺🇸 · Paul Reimer (1)🇺🇸 · Zhihong Ye (1)🇺🇸 · Jacques Ball (2)🇫🇷 and 44 other authors

   The three-dimensional picture of quarks and gluons in the proton is set to be revealed through Deeply virtual Compton scattering while a critically important puzzle in the one-dimensional picture remains, namely, the origins of the EMC effect. Incoherent nuclear DVCS, i.e. DVCS on a nucleon inside a nucleus, can reveal the 3D partonic structure of the bound nucleon and shed a new light on the EMC effect. However, the Fermi motion of the struck nucleon, off-shell effects and final-state interactions (FSIs) complicate this parton level interpretation. We propose here a measurement of incoherent DVCS with a tagging of the recoiling spectator system (nucleus A-1) to systematically control nuclear effects. Through spectator-tagged DVCS, a fully detected final state presents a unique opportunity to systematically study these nuclear effects and cleanly observe possible modification of the nucleon's quark distributions. We propose to measure the DVCS beam-spin asymmetries (BSAs) on ${}^4$He and deuterium targets. The reaction ${}^4$He$(e,e^{\prime }\gamma p{}^3$H$)$ with a fully detected final state has the rare ability to simultaneously quantify FSIs, measure initial nucleon momentum, and provide a sensitive probe to other nuclear effects at the parton level. The DVCS BSA on a (quasi-free) neutron will be measured by tagging a spectator proton with a deuteron target. Similarly, a bound neutron measurement detects a spectator ${}^3$He off a ${}^4$He target. These two observables will allow for a self-contained measurement of the neutron off-forward EMC Effect.

   nucl-ex11 citations
3. 03*

   The Casimir-Polder interaction between two neutrons and possible relevance to tetraneutron states

   M. S. Hussein🇧🇷 · J. Babb🇺🇸 · R. Higa🇧🇷

   We present a summary of our recent publication concerning the derivation of the extended Casimir-Polder dispersive interaction between two neutrons. Dynamical polarizations of the neutrons, recently derived within Chiral Effective Theory are used for the purpose. An account of the higher frequency/energy behavior of these entities related to the opening of one-pion production channel and the excitation of the $\Delta$ resonance are taken into consideration in our derivation of the CP interaction. The neutron-neutron system in free space is treated in details so are the neutron-wall and the wall-neutron-wall systems. The case of tetraneutron (a 4 neutron system) in a resonant state is then briefly considered. The 4n CP interaction is evaluated to assess its potential relevance to the ongoing debate concerning the nature of the tetraneutron.

   ↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2017)·2 citations
4. 04*

   Intrinsic properties of high-spin band structures in triaxial nuclei

   S. Jehangir · G.H. Bhat🇮🇳 · J.A. Sheikh · R. Palit🇮🇳 · P.A. Ganai

   The band structures of ${}^{68,70}$Ge, ${}^{128,130,132,134}$Ce and ${}^{132,134,136,138}$Nd are investigated using the triaxial projected shell model (TPSM) approach. These nuclei depict forking of the ground-state band into several s-bands and in some cases, both the lowest two observed s-bands depict neutron or proton character. It was discussed in our earlier work that this anamoluos behaviour can be explained by considering $\gamma$-bands based on two-quasiparticle configurations. As the parent band and the $\gamma$-band built on it have the same intrinsic structure, g-factors of the two bands are expected to be similar. In the present work, we have undertaken a detailed investigation of g-factors for the excited band structures of the studied nuclei and the available data for a few high-spin states are shown to be in fair agreement with the predicted values.

   ↳ nucl-thnucl-exNPA(2017)·18 citations
5. 05*

   The s-process nucleosynthesis: impact of the uncertainties in the nuclear physics determined by Monte Carlo variations

   G. Cescutti · N. Nishimura🇬🇧 · R. Hirschi🇬🇧 · T. Rauscher🇬🇧 · J. W. den Hartogh · A. St. J. Murphy🇬🇧

   We investigated the impact of uncertainties in neutron-capture and weak reactions (on heavy elements) on the s-process nucleosynthesis in low-mass stars and massive stars using a Monte-Carlo based approach. We performed extensive nuclear reaction network calculations that include newly evaluated temperature-dependent upper and lower limits for the individual reaction rates. We found beta-decay rate uncertainties affect only a few nuclei near s-process branchings, whereas most of the uncertainty in the final abundances is caused by uncertainties in the neutron capture rates. We suggest a list of uncertain rates as candidates for improved measurement by future experiments.

   ↳ astro-ph.SRnucl-exnucl-thMem.Soc.Ast.It.(2017)·1 citation

* 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.