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Albaladejo, M., & Oset, E. (2013). Combined analysis of the pn -> d pi(+)pi(-) and pn -> pn pi(+)pi(-) cross sections and implications for the interpretation of the pn -> d pi(+)pi(-) data. Phys. Rev. C, 88(1), 014006–6pp.
Abstract: We use recent data that show a narrow peak around root s = 2.37 GeV in the pn -> d pi(+)pi(-) cross section, with about double strength at the peak than in the analogous pn -> d pi(0)pi(0) reaction, and, assuming that it is due to the excitation of a dibaryon resonance, we evaluate the cross section for the pn -> pn pi(+)pi(-) reaction, with the final pn unbound but with the same quantum numbers as the deuteron. We use accurate techniques to determine the final state interaction in the case of the pn forming a deuteron or a positive energy state, which allow us to get the pn -> pn pi(+)pi(-) cross section with pn in I = 0 and S = 1, that turns out to be quite close or saturates the experimental pn -> pn pi(+)pi(-) total cross section around root s = 2.37 GeV, depending on the angular momentum assumed. This poses problems to the assumption of the dibaryon hypothesis, which could be rendered more restrictive with future precise data on the pn -> pn pi(+)pi(-) reaction.
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Perez-Cerdan, A. B., Rubio, B., Gelletly, W., Algora, A., Agramunt, J., Nacher, E., et al. (2013). Deformation of Sr and Rb isotopes close to the N = Z line via beta-decay studies using the total absorption technique. Phys. Rev. C, 88(1), 014324–15pp.
Abstract: A study of the Gamow-Teller strength distributions B(GT) in the beta decay of Sr-78 and Rb-76,Rb-78 has been made using a total absorption spectrometer (TAS). Following the success in deducing the sign of the deformation for Sr-76, a similar approach is adopted for Sr-78 based on a comparison of the measured B(GT) with quasiparticle random-phase approximation calculations. This work confirms its previously expected prolate deformation in the ground state. Conclusions about the structure of the odd-odd Rb-76,Rb-78 isotopes have been drawn based on their measured B(GT) distributions.
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Soderstrom, P. A. et al, & Montaner-Piza, A. (2013). Shape evolution in Ru-116,Ru-118: Triaxiality and transition between the O(6) and U(5) dynamical symmetries. Phys. Rev. C, 88(2), 024301–10pp.
Abstract: Ru-116 and Ru-118 have been studied via beta-delayed gamma-ray spectroscopy of nuclei produced in fragmentation reactions at the Radioactive Ion-Beam Factory (RIBF) facility. Level schemes with positive-parity states up to spin J = 6 have been constructed. The results have been discussed in terms of the interacting boson model, the algebraic collective model, and total Routhian surfaces. We conclude that the very neutron-rich nuclei still show many features associated with triaxial gamma-soft nuclei, represented by the O(6) symmetry, but are approaching a spherical structure, the U(5) symmetry, with increasing neutron number towards the N = 82 shell closure. In Ru-118, hints of a shape transition in the ground state have been observed.
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Vandone, V. et al, Gadea, A., & Huyuk, T. (2013). Global properties of K hindrance probed by the gamma decay of the warm rotating W-174 nucleus. Phys. Rev. C, 88(3), 034312–9pp.
Abstract: The K hindrance to the gamma decay is studied in the warm rotating W-174 nucleus, focusing on the weakening of the selection rules of the K quantum number with increasing excitation energy. W-174 was populated by the fusion reaction of Ti-50 (at 217 MeV) on a Te-128 target, and its gamma decay was detected by the AGATA Demonstrator array coupled to a BaF2 multiplicity filter at Laboratori Nazionali di Legnaro of INFN. A fluctuation analysis of gamma coincidence matrices gives a similar number of low-K and high-K discrete excited bands. The results are compared to simulations of the gamma-decay flow based on a microscopic cranked shell model at finite temperature in which the K mixing is governed by the interplay of Coriolis force with the residual interaction. Agreement between simulations and experiment is obtained only by hindering the E1 decay between low-K and high-K bands by an amount compatible with that determined by spectroscopic studies of K isomers in the same mass region, with a similar trend with excitation energy. The work indicates that K mixing due to temperature effects may play a leading role for the entire body of discrete excited bands, which probes the onset region of K weakening.
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Mason, P. J. R. et al, & Algora, A. (2013). Half-life of the yrast 2(+) state in W-188: Evolution of deformation and collectivity in neutron-rich tungsten isotopes. Phys. Rev. C, 88(4), 044301–6pp.
Abstract: The half-life of the yrast I-pi = 2(+) state in the neutron-rich nucleus W-188 has been measured using fast-timing techniques with the HPGe and LaBr3:Ce array at the National Institute of Physics and Nuclear Engineering, Bucharest. The resulting value of t(1/2) = 0.87(12) ns is equivalent to a reduced transition probability of B(E2;2(1)(+) -> 0(1)(+)) = 85(12) W.u. for this transition. The B(E2;2(1)(+) -> 0(1)(+)) is compared to neighboring tungsten isotopes and nuclei in the Hf, Os, and Pt isotopic chains. Woods-Saxon potential energy surface (PES) calculations have been performed for nuclei in the tungsten isotopic chain and predict prolate deformed minima with rapidly increasing gamma softness for W184-192 and an oblate minimum for W-194.
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