Probabilities for two-neutron transfer reactions, $P_{ \rm 2n}$, are often discussed in comparison with the square of the corresponding probabilities for one-neutron transfer process, $(P_{ \rm 1n})^2$, implicitly assuming that $(P_{ \rm 1n})^2$ provides the probability of two-neutron transfer reactions in the absence of the pairing correlation. We use a schematic coupled-channels model, in which the transfers are treated as effective inelastic channels, and demonstrate that this model leads to $P_{ \rm 2n}=(P_{ \rm 1n})^2/4$, rather than $P_{ \rm 2n}=(P_{ \rm 1n})^2$, in the pure sequential limit. We argue that a simple model with spin-up and spin-down neutrons in a single-particle orbital also leads to the same conclusion.
Categories: nucl-th nucl-ex