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Theoretical study of the $alpha+d$ $rightarrow$ $^6$Li + $gamma $ astrophysical capture process in a three-body model

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 نشر من قبل Ergash Tursunov M.
 تاريخ النشر 2016
  مجال البحث فيزياء
والبحث باللغة English
 تأليف E.M. Tursunov




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The astrophysical capture process $alpha+d$ $rightarrow$ $^6$Li + $gamma$ is studied in a three-body model. The initial state is factorized into the deuteron bound state and the $alpha+d$ scattering state. The final nucleus $^6$Li(1+) is described as a three-body bound state $alpha+n+p$ in the hyperspherical Lagrange-mesh method. The contribution of the E1 transition operator from the initial isosinglet states to the isotriplet components of the final state is estimated to be negligible. An estimation of the forbidden E1 transition to the isosinglet components of the final state is comparable with the corresponding results of the two-body model. However, the contribution of the E2 transition operator is found to be much smaller than the corresponding estimations of the two-body model. The three-body model perfectly matches the new experimental data of the LUNA collaboration with the spectroscopic factor 2.586 estimated from the bound-state wave functions of $^6$Li and deuteron.



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The astrophysical S-factor and reaction rate of the direct capture process $alpha+d$ $rightarrow$ $^6$Li + $gamma$, as well as the abundance of the $^6$Li element are estimated in a three-body model. The initial state is factorized into the deuteron bound state and the $alpha+d$ scattering state. The final nucleus $^6$Li(1+) is described as a three-body bound state $alpha+n+p$ in the hyperspherical Lagrange-mesh method. Corrections to the asymptotics of the overlap integral in the S- and D-waves have been done for the E2 S-factor. The isospin forbidden E1 S-factor is calculated from the initial isosinglet states to the small isotriplet components of the final $^6$Li(1+) bound state. It is shown that the three-body model is able to reproduce the newest experimental data of the LUNA collaboration for the astrophysical S-factor and the reaction rates within the experimental error bars. The estimated $^6$Li/H abundance ratio of $(0.67 pm 0.01)times 10^{-14}$ is in a very good agreement with the recent measurement $(0.80 pm 0.18)times 10^{-14}$ of the LUNA collaboration.
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