Search results for "SIP"
showing 10 items of 1280 documents
Mean-field effects on neutrinoless double beta decay
1998
Abstract Mean-field effects on the nuclear matrix elements involved in the neutrinoless double beta (0νββ) decay of several double-electron and double-positron emitters have been studied within the framework of the relativistic quark-confinement model and the quasiparticle random-phase approximation. The single-particle energies of the model space have been generated both by using the standard Woods-Saxon parametrization of the mean field and adjusting the quasiparticle spectra with the data from neutron- and proton-odd nuclei. The 0νββ rates are found to be much less affected by the energies of the mean-field orbitals than the rates of the two-neutrino double beta decay. The present study …
On the double-beta decays of 70Zn, 86Kr, 94Zr, 104Ru, 110Pd and 124Sn
2011
Abstract Double-beta decays of 70Zn, 86Kr, 94Zr, 104Ru, 110Pd and 124Sn to the final ground states and the decays of 110Pd and 124Sn to the excited states in 110Cd and 124Te are studied in the framework of the proton–neutron quasiparticle random-phase approximation (pnQRPA) combined with the multiple-commutator model (MCM) for description of decays to the excited final states. Reasonably large single-particle model spaces and G-matrix-based effective nuclear forces are used to compute the relevant nuclear matrix elements and decay half-lives. The present study is among the very few that have been dedicated to double-beta decays of these nuclei, although the associated double-beta Q values e…
Theory of double beta decay
2005
Basic features of the two-neutrino double beta ( 2 ν β β ) decay and neutrinoless double beta ( 0 ν β β ) decay are discussed. A short review of the most important nuclear models, used to describe the ββ decay, is given. A deeper survey of the nuclear matrix elements, related to the above-mentioned decay modes, is performed using the proton-neutron quasiparticle random-phase approximation (pnQRPA). In particular, the extraction of a proper value of the proton-neutron particle-particle interaction parameter in this theory is addressed. The relevance of different multipoles in the multipole decomposition of the 0 ν β β matrix element is also discussed in the pnQRPA framework.
Probing the quenching of gA by single and double beta decays
2013
Abstract Ground-state-to-ground-state two-neutrino double beta ( 2 ν β β ) decays and single beta (EC and β − ) decays are studied for the A = 100 (100Mo 100Tc 100Ru), A = 116 (116Cd 116In 116Sn) and A = 128 (128Te 128I 128Xe) nuclear systems by using the proton–neutron quasiparticle random-phase approximation exploiting realistic effective interactions in very large single-particle bases. The aim of this exercise is to see if both the single-beta and double-beta decay observables related to the ground states of the initial, intermediate and final nuclei participant in the decays can be described simultaneously by changing the value of the axial-vector coupling constant g A . In spite of th…
Quasimolecular resonances in terms of dipole and quadrupole interacting bosons
1986
The energy spectrum of the /sup 12/C+ /sup 12/C resonances is described with the interacting boson (quadrupole) model. The Hamiltonians corresponding to the three dynamical symmetries and to the general case of the model are used. The results are compared with the similar calculations within the nuclear vibron (dipole) model. Based on the present experimental data no choice can be made between the dipole and quadrupole descriptions, but in both cases the best fit is quite close to the dynamical symmetry corresponding to a soft vibrator.
Study of band crossings in 130Xe
1984
Abstract Excited states in 130Xe were populated in the reaction 130 Te (α, 4 n ) , and the subsequent de-excitation was studied using in-beam γ-ray spectroscopic methods. High-spin states were observed to a possible spin of 19 kh at an excitation energy of 7 MeV. Band-crossings due to h 11 2 neutrons and protons were observed. The triaxial cranked shell model was applied in order to study the quasiparticle content of different bands. Excitation energies of two-quasiparticle states were calculated in the framework of the semiempirical shell model.
Energy damping and intermediate-velocity fragment emission in peripheral Kr+Au collisions at 43 MeV/u
1992
Abstract Triple and four-fold coincidences among fragments have been measured in the reaction 84 Kr+Au at 43 MeV/u. All events showing the projectile-like nucleus and fission fragments of the target-like nucleus, and all events with one additional intermediate-velocity fragment, were analysed in the frame of a dissipative collision and a participant-spectator model. The mechanism is basically that of a dissipative collision but the emission of the intermediate velocity fragment by the target differs from an equilibrated evaporation.
Coexistence of collective and quasiparticle structures in 106Sn and 108Sn
1997
New levels in the neutron deficient nuclei 106Sn and 108Sn have been investigated by using the NORDBALL detector array combined with charged particle and neutron detectors. The excited structures are discussed in terms of collectivity and the shell model. The excitations are interpreted to be based on d52, g72 and h112 both for protons and neutrons and g92 for protons. The systematical behaviour of the specific states in the Sn isotopes is studied in the mass range of A = 106–118.
Fractional characteristic times and dissipated energy in fractional linear viscoelasticity
2016
Abstract In fractional viscoelasticity the stress–strain relation is a differential equation with non-integer operators (derivative or integral). Such constitutive law is able to describe the mechanical behavior of several materials, but when fractional operators appear, the elastic and the viscous contribution are inseparable and the characteristic times (relaxation and retardation time) cannot be defined. This paper aims to provide an approach to separate the elastic and the viscous phase in the fractional stress–strain relation with the aid of an equivalent classical model (Kelvin–Voigt or Maxwell). For such equivalent model the parameters are selected by an optimization procedure. Once …
Mixed mode failure analysis of bonded joints with rate dependent interface models
2006
The recent developments in joining technologies and the increasing use of composites materials in structural design justify the wide interest of structural mechanics researchers in bonded joints. Joints often represent the weakness zone of the structure and appropriate and rigorous mechanical models are required in order to describe deformation, durability and failure. The present work is devoted to the theoretical formulation and numerical implementation of an interface model suitable to simulate the time-dependent behaviour of bonded joints. The interface laws are formulated in the framework of viscoplasticity for generalized standard materials and describe the softening response of the j…