The study of dependence of beta decay half lives in R process nuclei on N and Z

In this study, the dependence of the log(ft) values for Gamow-Teller ß± transitions in r process nuclei near N=28, Z=50 region on neutron and proton number has been studied by using Pyatov Method within the framework of Quasiparticle Random Phase Approximation(QRPA). Within this purpose, first of all, the log(ft) values for 74-80Zn isotopes have been calculated, and then the graph of half lives obtained by using the log(ft) values for these isotopes against neutron number has been plotted. Our calculation results show that our half life values increase when the neutron number increases as it was in case of the experimental and other theoretical studies. However, our values are 10 times smaller than the experimental ones. It can be said that our values stil are not too far away from the experimental values. It is considered that in order to make our values closer to the experimental values, the values for neutron proton pairing correlations(Cn and Cp) which are different from Chepurnov parametrization in literature may be taken. Secondly, in order to see whether the change in the neutron proton pairing correlation values has an important effect on the log(ft) values, the log(ft) values for 74-80Zn isotopes have been calculated by changing the neutron proton pairing correlation values from Cn=Cp=10/ to Cn= Cp =2/ . According to our calculation results, it can be said that there is no important change in log(ft) values for ß- transitions while energy values are decreasing. However, a noticable change in log(ft) values for ß+ transitions occurs. Finally, in order to see dependence of half life values on proton number, the log (ft) values for Z=30 and Z=32 nuclei have been calculated by using the neutron-proton pairing correlation values(Cn and Cp)obtained by Chepurnov parametrization, and then the graph pf the half life values against proton number has been plotted. It has been seen that as it was in experimental and other theoretical studies, our half life values increase as the proton number increases, but our calculated values are still 10 times smaller than the corresponding experimental values.