Wed·Apr 26, 2017Wednesday·April 26, 2017

1. 01*

   Simultaneous investigation of the $\mathbf{T}=1({\mathbf{J}}^{\pi }=0^{+})$ and $\mathbf{T}=0({\mathbf{J}}^{\pi }=9^{+})$ $\beta$ decays in ${}^{70}$Br

   A.I. Morales · A. Algora · B. Rubio · K. Kaneko · S. Nishimura · P. Aguilera · S.E.A. Orrigo · F. Molina · G. de Angelis · F. Recchia · G. Kiss · V. H. Phong and 46 other authors

   The $\beta$ decay of the odd-odd nucleus ${}^{70}$Br has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The $T=0$ ($J^{\pi }=9^{+}$) and $T=1$ ($J^{\pi }=0^{+}$) isomers have both been produced in in-flight fragmentation of ${}^{78}$Kr with ratios of 41.6(8)\% and 58.4(8)\%, respectively. A half-life of $t_{1/2}=2157_{-49}^{+53}$ ms has been measured for the $J^{\pi }=9^{+}$ isomer from $\gamma$-ray time decay analysis. Based on this result, we provide a new value of the half-life for the $J^{\pi }=0^{+}$ ground state of ${}^{70}$Br, $t_{1/2}=78.42\pm 0.51$ ms, which is slightly more precise, and in excellent agreement, with the best measurement reported hitherto in the literature. For this decay, we provide the first estimate of the total branching fraction decaying through the $2_1^{+}$ state in the daughter nucleus ${}^{70}$Se, $R(2_1^{+})=1.3\pm 1.1\%$. We also report four new low-intensity $\gamma$-ray transitions at 661, 1103, 1561, and 1749 keV following the $\beta$ decay of the $J^{\pi }=9^{+}$ isomer. Based on their coincidence relationships, we tentatively propose two new excited states at 3945 and 4752 keV in ${}^{70}$Se with most probable spins and parities of $J^{\pi }=(6^{+})$ and $(8^{+})$, respectively. The observed structure is interpreted with the help of shell-model calculations, which predict a complex interplay between oblate and prolate configurations at low excitation energies.

   nucl-exPRC(2017)·24 citations
2. 02*

   Re-measurement of the ${}^{33}$S($\alpha$,p)${}^{36}$Cl cross section for Early solar system enrichment

   Tyler Anderson🇺🇸 · Michael Skulski · Adam Clark · Austin Nelson🇺🇸 · Karen Ostdiek · Philippe Collon · Greg Chmiel · Tom Woodruff · Marc Caffee🇺🇸

   Short-lived radionuclides (SLRs) with half-lives less than 100 Myr are known to have existed around the time of the formation of the solar system around 4.5 billion years ago. Understanding the production sources for SLRs is important for improving our understanding of processes taking place just after solar system formation as well as their timescales. Early solar system models rely heavily on calculations from nuclear theory due to a lack of experimental data for the nuclear reactions taking place. In 2013, Bowers et al. measured ${}^{36}$Cl production cross sections via the ${}^{33}$S($\alpha$,p) reaction and reported cross sections that were systematically higher than predicted by Hauser-Feshbach codes. Soon after, a paper by Peter Mohr highlighted the challenges the new data would pose to current nuclear theory if verified. The ${}^{33}$S($\alpha$,p)${}^{36}$Cl reaction was re-measured at 5 energies between 0.78 MeV/A and 1.52 MeV/A, in the same range as measured by Bowers et al., and found systematically lower cross sections than originally reported, with the new results in good agreement with the Hauser-Feshbach code TALYS. Loss of Cl carrier in chemical extraction and errors in determination of reaction energy ranges are both possible explanations for artificially inflated cross sections measured in the previous work.

   nucl-exPRC(2017)·8 citations
3. 03*

   Nucleon momentum distributions in ${}^3$He and three-body interactions

   S.V.Bekh · A.P.Kobushkin · E.A.Strokovsky

   We calculate momentum distributions of neutrons and protons in ${}^3$He in the framework of a model which includes 3N interactions together with 2N interactions. It is shown that contribution of 3N interactions becomes essential in comparison with contribution coming from 2N interaction for internal momentum in ${}^3$He $k>$~250~MeV/c. We also compare calculated momentum distribution of protons with so-called empirical momentum distribution of protons extracted from A${(}^3\mathrm{He},p)$ breakup cross-sections measured for protons emitted at zero degree. It is concluded that 3N interactions cannot completely explain the disagreement between the available data on the empirical momentum distribution of protons in ${}^3\mathrm{He}$ and calculations based on 2N interaction, which is observed at high momentum region of the momentum distribution, $k>$~250~MeV/c.

   ↳ nucl-thnucl-exUkr.J.Phys.(2017)·1 citation
4. 04*

   Determination of Quark-Gluon-Plasma Parameters from a Global Bayesian Analysis

   Steffen A. Bass🇺🇸 · Jonah E. Bernhard🇺🇸 · J. Scott Moreland🇺🇸

   The quality of data taken at RHIC and LHC as well as the success and sophistication of computational models for the description of ultra-relativistic heavy-ion collisions have advanced to a level that allows for the quantitative extraction of the transport properties of the Quark-Gluon-Plasma. However, the complexity of this task as well as the computational effort associated with it can only be overcome by developing novel methodologies: in this paper we outline such an analysis based on Bayesian Statistics and systematically compare an event-by-event heavy-ion collision model to data from the Large Hadron Collider. We simultaneously probe multiple model parameters including fundamental quark-gluon plasma properties such as the temperature-dependence of the specific shear viscosity $\eta /s$, calibrate the model to optimally reproduce experimental data, and extract quantitative constraints for all parameters simultaneously. The method is universal and easily extensible to other data and collision models.

   ↳ nucl-thhep-phnucl-exNPA(2017)·47 citations
5. 05*

   $A$-dependence of quasielastic charged-current neutrino-nucleus cross sections

   Nils Van Dessel🇧🇪 · Natalie Jachowicz🇧🇪 · Raúl González-Jiménez🇧🇪 · Vishvas Pandey🇺🇸 · Tom Van Cuyck🇧🇪

   Background: 12C has been and is still widely used in neutrino-nucleus scattering and oscillation experiments. More recently, 40Ar has emerged as an important nuclear target for current and future experiments. Liquid argon time projection chambers (LArTPCs) possess various advantages in measuring electroweak neutrino-nucleus cross sections. Concurrent theoretical research is an evident necessity. Purpose: 40Ar is larger than 12C, and one expects nuclear effects to play a bigger role in reactions. We present inclusive differential and total cross section results for charged-current neutrino scattering on 40Ar and perform a comparison with 12C, 16O and 56Fe targets, to find out about the A-dependent behavior of model predictions. Method: Our model starts off with a Hartree-Fock description of the nucleus, with the nucleons interacting through a mean field generated by an effective Skyrme force. Long-range correlations are introduced by means of a continuum random phase approximation (CRPA) approach. Further methods to improve the accuracy of model predictions are also incorporated in the calculations. Results: We present calculations for 12C, 16O, 40Ar and 56Fe, showcasing differential cross sections over a broad range of kinematic values in the quasielastic regime. We furthermore show flux-folded results for 40Ar and we discuss the differences between nuclear responses. Conclusions: At low incoming energies and forward scattering we identify an enhancement in the 40Ar cross section compared to 12C, as well as in the high $\omega$ (low $T_{\mu }$ ) region across the entire studied $E_{\nu }$ range. The contribution to the folded cross section of the reaction strength at values of $\omega$ lower than 50 MeV for forward scattering is sizeable.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2018)·26 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.