Investigation for the effect of particle-particle forces in two-neutrino beta decay

INVESTIGATION FOR THE EFFECT OF PARTICLE-PARTICLE FORCES IN TWO-NEUTRINO BETA DECAY Arslan ÜNAL Physics Department, M. S. Thesis, 2004 Thesis Supervisors: Prof. Atalay KÜÇÜKBURSA SUMMARY In this study, spin-spin interaction with charge-exchange among to nuclei is investigated in the particle-hole and particle-particle channel using Woods-Saxon potential through Quasi Random Phase Approximation (QRPA). Nuclear Matrix Elements (NME) of two-neutrino double beta decay are calculated by taking into the account deformation cases of nuclear structure. The calculations are carried out for the mother and daughter nuclei having the ground states same and different cases. The calculations indicated that estimated value of NME decrease when Gamow-Teller (G-T) effective interaction is taken in the account the particle-particle channel among the nucleons. But the decrease is not sufficient to provide agreement between predicted theoretical values and experimental values for some nuclei. Although the calculation values for some of the investigated nuclei are in agreement with the experimental results, the values of some other investigated nuclei are higher than in 3-5 order from experimental values. We think that the difference can be removed by considering two particle-two hole interactions and harmonic terms in the within QRPA method. Key Words: Nuclear Matrix Element, Two Neutrino Double Beta Decay.