Thu·Jul 17, 2014Thursday·July 17, 2014

1. 01*

   Single Particle Strengths and Mirror States in ${}^{15}$N${-}^{15}$O below 12.0 MeV

   C. E. Mertin · D. D. Caussyn🇺🇸 · A. M. Crisp · N. Keeley🇫🇷 · K. W. Kemper🇺🇸 · O. Momtyuk · B. T. Roeder🇺🇸 · A. Volya🇺🇸

   New ${}^{14}$N(d,p) angular distribution data were taken at a deuteron bombarding energy of 16 MeV to locate all narrow single particle neutron states up to 15 MeV in excitation. A new shell model calculation is able to reproduce all levels in ${}^{15}$N up to 11.5 MeV and is used to characterize a narrow single particle level at 11.236 MeV and to provide a map of the single particle strengths. The known levels in ${}^{15}$N are then used to determine their mirrors in the lesser known nucleus ${}^{15}$O. The 2s${}_{1/2}$ and 1d${}_{5/2}$ single particle centroid energies are determined for the ${}^{15}$N${-}^{15}$O mirror pair as: ${}^{15}$N $({\text{2s}}_{1/2})=8.08$ MeV, ${}^{15}$O $({\text{2s}}_{1/2})=7.43$ MeV, ${}^{15}$N $({\text{1d}}_{5/2})=7.97$ MeV, and ${}^{15}$O $({\text{1d}}_{5/2})=7.47$ MeV. These results confirm the degeneracy of these orbits and that the ${}^{15}$N${-}^{15}$O nuclei are where the transition between the ${\text{2s}}_{1/2}$ lying below the ${\text{1d}}_{5/2}$ to lying above it, takes place. The ${\text{1d}}_{3/2}$ single particle strength is estimated to be centered around 13 MeV in these nuclei.

   nucl-exPRC(2015)·9 citations
2. 02*

   Phenomenology of Rate-Related Nonlinear Effects in Nuclear Spectroscopy

   J.M. Nistor🇺🇸 · J.M. Heim🇺🇸 · E. Fischbach🇺🇸 · J.H. Jenkins🇺🇸 · P.A. Sturrock🇺🇸

   A series of recent reports suggest that the decay rates of several isotopes may have been influenced by solar activity (perhaps by solar neutrinos). A mechanism in which neutrinos or antineutrinos can influence the decay process suggests that a sample of decaying nuclei emitting neutrinos could affect its own rate of decay. Past experiments have searched for this 'self-induced decay' (SID) effect by measuring deviations from the expected decay rate for highly active samples of varying geometries. Here, we show that the SID effect closely resembles the behavior of rate-related losses due to dead-time, and hence that standard dead-time corrections can result in the removal of any SID-related behavior. We conclude by describing experiments which could disentangle SID effects from those arising from dead-time.

   nucl-exhep-phphysics.ins-det1 citation
3. 03*

   Examination of the role of the ${}^{14}$O($\alpha$,$p$)${}^{17}$F reaction rate in type I x-ray bursts

   J. Hu🇩🇪 · J.J. He🇨🇳 · A. Parikh🇪🇸 · S.W. Xu🇨🇳 · H. Yamaguchi🇯🇵 · D. Kahl · P. Ma🇨🇳 · J. Su🇨🇳 · H.W. Wang🇨🇳 · T. Nakao🇯🇵 · Y. Wakabayashi🇯🇵 · T. Teranishi🇯🇵 and 8 other authors

   The ${}^{14}$O($\alpha$,$p$)${}^{17}$F reaction is one of the key reactions involved in the breakout from the hot-CNO cycle to the rp-process in type I x-ray bursts (XRBs). The resonant properties in the compound nucleus ${}^{18}$Ne have been investigated through resonant elastic scattering of ${}^{17}$F+$p$. The radioactive ${}^{17}$F beam was separated by the CNS Radioactive Ion Beam separator (CRIB) and bombarded a thick H${}_2$ gas target at 3.6 MeV/nucleon. The recoiling light particles were measured by three $\Delta$E-E silicon telescopes at laboratory angles of $\theta$${}_{lab}$$\approx$3${}^{\circ }$, 10${}^{\circ }$ and 18${}^{\circ }$, respectively. Five resonances at $E_x$=6.15, 6.28, 6.35, 6.85, and 7.05 MeV were observed in the excitation functions, and their spin-parities have been determined based on an $R$-matrix analysis. In particular, $J^{\pi }$=1${}^{-}$ was firmly assigned to the 6.15-MeV state which dominates the thermonuclear ${}^{14}$O($\alpha$,$p$)${}^{17}$F rate below 2 GK. As well, a possible new excited state in ${}^{18}$Ne was observed at $E_x$=6.85$\pm$0.11 MeV with tentative $J$=0 assignment. This state could be the analog state of the 6.880 MeV (0${}^{-}$) level in the mirror nucleus ${}^{18}$O, or a bandhead state (0${}^{+}$) of the six-particle four-hole (6$p$-4$h$) band. A new thermonuclear ${}^{14}$O($\alpha$,$p$)${}^{17}$F rate has been determined, and the astrophysical impact of multiple recent rates has been examined using an XRB model. Contrary to previous expectations, we find only modest impact on predicted nuclear energy generation rates from using reaction rates differing by up to several orders of magnitude.

   nucl-exastro-ph.SRPRC(2014)·22 citations
4. 04*

   Light vector meson photoproduction in hadron-hadron and nucleus-nucleus collisions at the energies available at the CERN Large Hadron Collider

   G. Sampaio dos Santos🇧🇷 · M.V.T. Machado🇧🇷

   In this work we analyse the theoretical uncertainties on the predictions for the photoproduction of light vector mesons in coherent pp, pA and AA collisions at the LHC energies using the color dipole approach. In particular, we present our predictions for the rapidity distribution for rh0 and phi photoproduction and perform an analysis on the uncertainties associated to the choice of vector meson wavefunctionand the phenomenological models for the dipole cross section. Comparison is done with the recent ALICE analysis on coherent production of rho at 2.76 TeV in PbPb collisions.

   ↳ hep-phhep-exnucl-exPRC(2015)·40 citations
5. 05*

   Pairing in the continuum: the quadrupole response of the Borromean nucleus 6He

   L. Fortunato🇮🇹 · R. Chatterjee🇮🇳 · Jagjit Singh · A. Vitturi🇮🇹

   The ground state and low-lying continuum states of 6He are found within a shell model scheme, in a basis of two-particle states built out of continuum p-states of the unbound 5He nucleus, using a simple pairing contact-delta interaction. This accounts for the Borromean character of the bound ground state, revealing its composition. We investigate the quadrupole response of the system and we put our calculations into perspective with the latest experimental results. The calculated quadrupole strength distribution reproduces the narrow 2+ resonance, while a second wider peak is found at about 3.9 MeV above the g.s. energy.

   ↳ nucl-thnucl-exPRC(2014)·28 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.