Fri·Jun 27, 2014Friday·June 27, 2014

1. 01*

   $\alpha$-cluster structure of ${}^{18}$O

   M. L. Avila · G. V. Rogachev🇺🇸 · V. Z. Goldberg🇺🇸 · E. D. Johnson🇺🇸 · K. W. Kemper🇺🇸 · Yu. M. Tchuvil'sky · A. S. Volya🇺🇸

   Background: Clustering phenomena in $N\ne Z$ nuclei provide an opportunity to understand the interplay between cluster and nucleon degrees of freedom. Purpose:To study resonances in the ${}^{18}$O spectrum, populated in ${}^{14}$C+$\alpha$ elastic scattering. Method: The Thick Target Inverse Kinematics (TTIK) technique was used to measure the excitation function for the ${}^{14}$C+$\alpha$ elastic scattering. A 42 MeV ${}^{14}$C beam was used to populate states of excitation energy up to 14.9 MeV in ${}^{18}$O. The analysis was performed using a multi-level, multi-channel R-Matrix approach. Results: Detailed spectroscopic information, including spin-parities, partial $\alpha$- and neutron- decay widths and dimensionless reduced widths, was obtained for excited states in ${}^{18}$O between 8 and 14.9 MeV in excitation energy. Cluster-Nucleon Configuration Interaction Model calculations of the same quantities are performed and compared to the experimental results. Conclusions: Strong fragmentation of large $\alpha$-cluster strengths is observed in the spectrum of ${}^{18}$O making the $\alpha$-cluster structure of ${}^{18}$O quite different from the pattern of known quasi-rotational bands of alternating parity that are characteristic of $N=Z$, even-even nuclei like ${}^{16}$O and ${}^{20}$Ne.

   nucl-exPRC(2014)·51 citations
2. 02*

   Excitation of Giant Monopole Resonance in ${}^{208}$Pb and ${}^{116}$Sn Using Inelastic Deuteron Scattering

   D. Patel🇺🇸 · U. Garg🇺🇸 · M. Itoh🇯🇵 · H. Akimune🇯🇵 · G.P.A. Berg🇺🇸 · M. Fujiwara🇯🇵 · M.N. Harakeh🇳🇱 · C. Iwamoto🇯🇵 · T. Kawabata🇯🇵 · K. Kawase🇯🇵 · J.T. Matta🇺🇸 · T. Murakami🇯🇵 and 6 other authors

   The excitation of the isoscalar giant monopole resonance (ISGMR) in ${}^{116}$Sn and ${}^{208}$Pb has been investigated using small-angle (including $0^{\circ }$) inelastic scattering of 100 MeV/u deuteron and multipole-decomposition analysis (MDA). The extracted strength distributions agree well with those from inelastic scattering of 100 MeV/u $\alpha$ particles. These measurements establish deuteron inelastic scattering at E${}_d\sim$ 100 MeV/u as a suitable probe for extraction of the ISGMR strength with MDA, making feasible the investigation of this resonance in radioactive isotopes in inverse kinematics.

   nucl-exPLB(2014)·29 citations
3. 03*

   Break-up channels in muon capture on 3He

   J. Golak🇵🇱 · R. Skibinski🇵🇱 · H. Witała🇵🇱 · K. Topolnicki🇵🇱 · A.E. Elmeshneb🇵🇱 · H. Kamada🇯🇵 · A. Nogga🇩🇪 · L.E. Marcucci🇮🇹

   The mu + 2H -> nu + n + n, mu + 3He -> nu + 3H, mu + 3He -> nu + n + d and mu + 3He -> nu + n + n + p capture reactions are studied with various realistic potentials under full inclusion of final state interactions. Our results for the two- and three-body break-up of 3He are calculated with a variety of nucleon-nucleon potentials, among which is the AV18 potential, augmented by the Urbana~IX three-nucleon potential. Most of our results are based on the single nucleon weak current operator. As a first step, we have tested our calculation in the case of the mu + 2H -> nu + n + n and mu + 3He -> nu + 3H reactions, for which theoretical predictions obtained in a comparable framework are available. Additionally, we have been able to obtain for the first time a realistic estimate for the total rates of the muon capture reactions on 3He in the break-up channels: 544 1/s and 154 1/s for the n + d and n + n + p channels, respectively. Our results have also been compared with the most recent experimental data, finding a rough agreement for the total capture rates, but failing to reproduce the differential capture rates.

   ↳ nucl-thnucl-exPRC(2014)·26 citations
4. 04*

   GEANT4 simulation of the neutron background of the C${}_6$D${}_6$ set-up for capture studies at n_TOF

   n_TOF collaboration: P. Žugec🇭🇷 · N. Colonna🇮🇹 · D. Bosnar🇭🇷 · S. Altstadt🇩🇪 · J. Andrzejewski🇵🇱 · L. Audouin🇫🇷 · M. Barbagallo🇮🇹 · V. Bécares🇪🇸 · F. Bečvář🇨🇿 · F. Belloni🇫🇷 · E. Berthoumieux🇫🇷 · J. Billowes🇬🇧 and 94 other authors

   The neutron sensitivity of the C${}_6$D${}_6$ detector setup used at n_TOF for capture measurements has been studied by means of detailed GEANT4 simulations. A realistic software replica of the entire n_TOF experimental hall, including the neutron beam line, sample, detector supports and the walls of the experimental area has been implemented in the simulations. The simulations have been analyzed in the same manner as experimental data, in particular by applying the Pulse Height Weighting Technique. The simulations have been validated against a measurement of the neutron background performed with a ${}^{\mathrm{nat}}$C sample, showing an excellent agreement above 1 keV. At lower energies, an additional component in the measured ${}^{\mathrm{nat}}$C yield has been discovered, which prevents the use of ${}^{\mathrm{nat}}$C data for neutron background estimates at neutron energies below a few hundred eV. The origin and time structure of the neutron background have been derived from the simulations. Examples of the neutron background for two different samples are demonstrating the important role of accurate simulations of the neutron background in capture cross section measurements.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2014)·27 citations
5. 05*

   Ratio B(E2, 4\rightarrow2)/B(E2, 2\rightarrow 0) in Even-Even Nuclei:Apparent Anomalous Behavior of the Chromium Isotopes

   Daniel Hertz-Kintish · Larry Zamick🇺🇸

   We consider the ratio RE4 = B(E2,4\rightarrow2)/B(E2,2\rightarrow 0) for the lowest 2^{+} and 4^{+} states in even-even nuclei. In the rotatonal and vibrational models and the shell model calculations here considered, RE4 is greater than one, however empirically, using adopted values from NNDC for ^{48}Cr and ^{50} Cr this ratio is less than one.

   ↳ nucl-thnucl-exPRC(2014)·20 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.