Shell Model Monte Carlo for GamowTeller Strengths and TwoNeutrino Double Beta Decay.
Abstract
In this thesis, a method to calculate twoneutrino double beta decay matrix elements employing the Shell Model Monte Carlo is presented. This method is validated against directdiagonalization for the decay of ^ {48}Ca. The first realistic calculation of the nuclear matrix element within the shell model for ^{76}Ge is performed; the result is in reasonable agreement with experiment. The sensitivity of the shell model results to the nuclear Hamiltonian has been studied for the case of ^{48}Ca where the Hamiltonian used is known to be an optimal one. While one cannot make the nuclear matrix element arbitrarily small, the uncertainty in certain pieces of the Hamiltonian such as the monopole isovector pairing, provides room for at least a factor of two in the matrix element (and hence a factor of four in the halflife) from such calculations. A Maximum Entropy method to obtain realistic strength functions from imaginary time response functions has been applied to GamowTeller response functions calculated using the Shell Model Monte Carlo and the results are validated against directdiagonalization and experiment. Future prospects for double beta decay calculations and astrophysical applications of the GamowTeller strength functions are briefly discussed.
 Publication:

Ph.D. Thesis
 Pub Date:
 August 1996
 Bibcode:
 1996PhDT........40B
 Keywords:

 Physics: Nuclear; Physics: Elementary Particles and High Energy