Nuclear Theory·nucl-th

Thursday·August 16, 2018

10 papers—2 primary·8 cross-listed

01
$0 ν β β$ nuclear matrix elements, neutrino potentials and $SU (4)$ symmetry
Fedor Šimkovic · Adam Smetana · Petr Vogel
Intimate relation between the Gamow-Teller part of the matrix element $M_{GT}^{0 ν}$ and the $2 ν β β$ closure matrix element $M_{cl}^{2 ν}$ is explained and explored. If the corresponding radial dependence $C_{cl}^{2 ν} (r)$ would be known, $M^{0 ν}$ corresponding to any mechanism responsible for the $0 ν β β$ decay can be obtained as a simple integral. However, the $M_{cl}^{2 ν}$ values sensitively depend on the properties of higher lying $1^{+}$ states in the intermediate odd-odd nuclei. We show that the $β^{-}$ and $β^{+}$ amplitudes of such states typically have opposite relative signs, and their contributions reduce severally the $M_{cl}^{2 ν}$ values. Vanishing values of $M_{cl}^{2 ν}$ are signs of a partial restoration of the spin-isospin $SU (4)$ symmetry. We suggest that demanding that $M_{cl}^{2 ν}$ = 0 is a sensible way, within the method of the Quasi-particle Random Phase Approximation (QRPA), of determining the amount of renormalization of isoscalar particle-particle interaction strength $g_{pp}^{T = 0}$ . Using such prescription, the matrix elements $M^{0 ν}$ are evaluated; their values are not very different ( $\leq$ 20\%) from the usual QRPA values when $g_{pp}^{T = 0}$ is related to the known $2 ν β β$ half-lives.
nucl-thPRC(2018)·90 citations
02
Post breakup dynamics of fragments produced in nuclear multifragmentation
S. R. Souza🇧🇷 · B. V. Carlson🇧🇷 · R. Donangelo🇧🇷
The deexcitation of the primary hot fragments, produced in the breakup of an excited nuclear source, during their propagation under the influence of their mutual Coulomb repulsion is studied in the framework of a recently developed hybrid model. The latter is based on the Statistical Mul- tifragmentation Model (SMM), describing the prompt breakup of the source, whereas the particle emission from the hot fragments, that decay while traveling away from each other, is treated by the Weisskopf-Ewing evaporation model. Since this treatment provides an event by event descrip- tion of the process, in which the classical trajectories of the fragments are followed using molecular dynamics techniques, it allows one to study observables such as two-particle correlations and infer the extent to which the corresponding observables may provide information on the multifragment production mechanisms. Our results suggest that the framework on which these treatments are based may be considerably constrained by such analyses. Furthermore, they imply that information obtained from these model calculations may provide feedback to the theory of nuclear interferome- try. We also found that neutron deficient fragments should hold information more closely related to the breakup region than neutron rich ones, as they are produced in much earlier stages of the post breakup dynamics than the latter.
nucl-thnucl-exNPA(2019)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

0νββ nuclear matrix elements, neutrino potentials and SU(4) symmetry

Post breakup dynamics of fragments produced in nuclear multifragmentation

Affiliations

$0 ν β β$ nuclear matrix elements, neutrino potentials and $SU (4)$ symmetry