Abstract:
In this work a novel theoretical and computational method for computing
electroweak beta decay spectra of medium and heavy-mass nuclei, as well as
the electronic structure of atomic and molecular systems is developed. In
particular, starting from the phenomenological electroweak interaction of the
Standard Model (SM) of particles, a general expression of the beta decay rate
was derived. Relativistic effects are taken into account by solving the
many-electron Dirac equation from first-principles. Furthermore, an extension
of this approach to include the nucleon-nucleon interaction at the same level
of theory of the electronic correlations has been devised. It is shown that
post-collisional effects, and to a lesser extent the electronic exchange and
correlation, can modify significantly the cross-section only at low energies
(<10 keV), while nuclear correlations considerably affect the lineshape of both
the absorption and emission spectra particularly in odd-odd nuclear
transitions, where the independent particle approximation, on which the
nuclear shell model is framed, is more likely to fail. These findings
demonstrate the importance of moving beyond the independent particle
picture to obtain an accurate description of the experimental data by adding
the many-body correlations between the spectator and participator hadrons
and leptons involved in the decay. The application of our approach to a
number of test cases, such as the modeling of beta decay of 36Cl, 63Ni, 129I,
210Bi, 241Pu and of the electron capture of 138La3+, leads to an extremely good
agreement with the relevant experimental data. Finally, the extension of this
method to atomic and molecular systems by calculating the electronic
structures of 138La3+ and several isomers (MgCN, MgNC) and molecules
(HMgCN, MgCNO, and BrCF3) relevant to astrophysical scenarios is
presented. This method, which is capable to deal with both nucleonic and
electronic degrees of freedom, has far-reaching implications also in neutrino
physics and nuclear astrophysics.
Date of publication:
06/11/2018
Published in:
Advanced Theory and Simulation 1 (11), 1870030 (2018)