Pairing properties of the double-{\beta} emitter 116Cd

TL;DR

This study investigates the pairing properties of the double-beta decay candidate 116Cd, finding that the BCS approximation is valid for neutrons but not for protons, impacting theoretical decay calculations.

Contribution

It provides experimental evidence on neutron pairing in 116Cd and highlights the limitations of BCS approximation for protons in double-beta decay modeling.

Findings

No significant 0+ strength in excited states for neutrons.

BCS approximation valid for neutrons, not for protons.

Proton pair vibrations complicate decay matrix element calculations.

Abstract

The pairing properties of the neutrinoless double-$\beta$ decay candidate $^{116}$Cd have been investigated. Measurements of the two-neutron removal reactions on isotopes of $^{114,116}$Cd have been made in order to identify 0$^+$ strength in the residual nuclei up to $\approx$3 MeV. No significant $L=0$ strength has been found in excited states indicating that the Bardeen-Cooper-Schrieffer (BCS) approximation is a reasonable basis to describe the neutrons in the ground state. This approximation avoids complications in calculations of double-$\beta$ decay matrix elements that use the quasiparticle random-phase approximation (QRPA) techniques. However this is not the case for the protons, where pair vibrations are prevalent and the BCS approximation is no longer valid, complicating the use of traditional QRPA techniques for this system as a whole.