Enhancement factor for two-neutron transfer reactions with a schematic coupled-channels model

TL;DR

This paper investigates two-neutron transfer probabilities using a schematic coupled-channels model, revealing that the transfer probability is reduced by a factor of four compared to the naive square of one-neutron transfer probability, challenging common assumptions.

Contribution

The study introduces a simplified coupled-channels model showing that two-neutron transfer probability is a quarter of the square of one-neutron transfer probability in the sequential limit, providing a new perspective.

Findings

$P_{2n} = (P_{1n})^2/4$ in the model

Sequential transfer limit reduces two-neutron transfer probability

Single-particle model supports the same conclusion

Abstract

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.