Effect of pairing on one- and two-nucleon transfer below the Coulomb barrier: a time-dependent microscopic description

TL;DR

This study uses a time-dependent microscopic approach to analyze how pairing correlations influence one- and two-nucleon transfer reactions below the Coulomb barrier, revealing significant enhancement in transfer probabilities due to pairing.

Contribution

It introduces a simplified TDHF+BCS method to quantify pairing effects on transfer reactions and examines the impact of pairing interaction types on transfer probabilities.

Findings

Pairing correlations significantly enhance two-nucleon transfer probabilities.

The ratio P_{2n}/(P_{1n})^2 increases with decreasing energy, exceeding ten in deep sub-barrier regimes.

Transfer probabilities are mainly influenced by pairing strength, not the specific type of pairing interaction.

Abstract

The effect of pairing correlation on transfer reaction below the Coulomb barrier is investigated qualitatively and quantitatively using a simplified version of the Time-Dependent Hartree-Fock + BCS approach. The effect of particle number symmetry breaking on the description of reaction and dedicated methods to extract one and two-nucleon transfer probabilities (P_{1n} and P_{2n}) in a particle number symmetry breaking approach are discussed. Influence of pairing is systematically investigated in the ^{40}Ca+ ^{40,42,44,46,48,50}Ca reactions. A strong enhancement of the two-particle transfer probabilities due to initial pairing correlations is observed. This enhancement induces an increase of the ratio of probabilities P_{2n} / (P_{1n})^2 compared to the case with no pairing. It is shown that this ratio increases strongly as the center of mass energy decreases with a value that could be larger than ten in the deep sub-barrier regime. An analysis of the pair transfer sensitivity to the type of pairing interaction, namely surface, mixed or volume, used in the theory is made. It is found that the pair transfer is globally insensitive to the type of force and mainly depends on the pairing interaction strength.