Pair correlations in nuclei involved in neutrinoless double β decay:Ge76andSe76

Precision measurements were carried out to test the similarities between the ground states of $^{76}\mathrm{Ge}$ and $^{76}\mathrm{Se}$. The extent to which these two nuclei can be characterized as consisting of correlated pairs of neutrons in a BCS-like ground state was studied. The pair removal $(p,t)$ reaction was measured at the far forward angle of ${3}^{\ifmmode^\circ\else\textdegree\fi{}}$. The relative cross sections are consistent (at the 5% level) with the description of these nuclei in terms of a correlated pairing state outside the $N=28$ closed shells with no pairing vibrations. Data were also obtained for $^{74}\mathrm{Ge}$ and $^{78}\mathrm{Se}$.