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Nuclear Theory·nucl-th

Wednesday·November 30, 2016

11 papers—4 primary·7 cross-listed

All11Primary4Cross-lists7
  1. 01

    Effective restoration of dipole sum rules within the renormalized random-phase approximation

    N. Quang Hung · N. Dinh Dang · T. V. Nhan Hao · L. Tan Phuc

    The dipole excitations for calcium and zirconium isotopes are studied within the fully self-consistent Hartree-Fock mean field incorporated with the renormalized random-phase approximation (RRPA) using the Skyrme interaction SLy5. The RRPA takes into account the effect of ground-state correlations beyond RPA owing to the Pauli principle between the particle-hole pairs that form the RPA excitations as well as the correlations due to the particle-particle and hole-hole transitions, whose effects are treated here in an effective way. By comparing the RPA results with the RRPA ones, which are obtained for isoscalar (IS) and isovector (IV) dipole excitations in Ca and Zr, it is shown that ground-state correlations beyond the RPA reduce the IS transition strengths. They also shift up the energy of the lowest IV dipole state and slightly push down the peak energy of the IV giant dipole resonance. As the result, the energy-weighted sums of strengths of both IS and IV modes decrease, causing the violation of the corresponding energy-weight sum rules (EWSR). It is shown that this sum rule violation can be eliminated by taking into account the contribution of the particle-particle and hole-hole excitations together with the particle-hole ones in a simple and perturbative way. Consequently, the ratio of the energy-weighted sum of strengths of the pygmy dipole resonance to that of the giant dipole resonance increases.

    nucl-thPRC(2016)·2 citations
  2. 02

    The shapes of nuclei

    G.F. Bertsch

    Gerry Brown initiated some early studies on the coexistence of different nuclear shapes. The subject has continued to be of interest and is crucial for understanding nuclear fission. We now have a very good picture of the potential energy surface with respect to shape degrees of freedom in heavy nuclei, but the dynamics remain problematic. In contrast, the early studies on light nuclei were quite successful in describing the mixing between shapes. Perhaps a new approach in the spirit of the old calculations could better elucidate the character of the fission dynamics and explain phenomena that current theory does not model well.

    nucl-thIJMPE(2017)·5 citations
  3. 03

    Random matrix analysis of the monopole strength distribution in Pb

    A. P. Severyukhin · S. Aberg · N. N. Arsenyev · R. G. Nazmitdinov · K. N. Pichugin

    We study statistical properties of the spectrum of Pb in the energy region MeV. We use the Skyrme interaction SLy4 as our model Hamiltonian to create a single-particle spectrum and to analyze excited states. The finite-rank separable approximation for the particle-hole interaction enables us to perform the calculations in large configuration spaces. We show that while the position of the monopole resonance centroid is determined by one phonon excitations of , the phonon-phonon coupling is crucial for the description of a strength distribution of the spectrum. In fact, this coupling has an impact on the spectral rigidity which is shifted towards the random matrix limit of the Gaussian orthogonal ensembles.

    nucl-thPhys.Atom.Nucl.(2016)·7 citations
  4. 04

    Inclusive breakup of three-fragment weakly bound nuclei

    Brett V. Carlson · Tobias Frederico · Mahir S. Hussein

    The inclusive breakup of three-fragment projectiles is discussed within a four-body spectator model. Both the elastic breakup and the non-elastic breakup are obtained in a unified framework. Originally developed in the 80's for two-fragment projectiles such as the deuteron, in this paper the theory is successfully generalized to three-fragment projectiles. The expression obtained for the inclusive cross section allows the extraction of the incomplete fusion cross section, and accordingly generalizes the surrogate method to cases such as (t,p) and (t,n) reactions. It is found that two-fragment correlations inside the projectile affect in a conspicuous way the elastic breakup cross section. The inclusive non-elastic breakup cross section is calculated and is found to contain the contribution of a three-body absorption term that is also strongly influenced by the two-fragment correlations. This latter cross section contains the so-called incomplete fusion where more than one compound nuclei are formed. Our theory describes both stable weakly bound three-fragment projectiles and unstable ones such as the Borromean nuclei.

    nucl-thnucl-exPLB(2017)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE