Quenching of Single-Particle Strength in A=15 Nuclei

TL;DR

This study measures neutron addition cross sections to $^{14}$C and $^{14}$N, revealing a significant quenching of single-particle strength, contrasting with previous knockout reaction results, using a simultaneous measurement approach.

Contribution

It provides new experimental data on neutron transfer in A=15 nuclei and highlights the quenching of single-particle strength, challenging previous interpretations from knockout reactions.

Findings

Neutron and proton separation energy differences are around -20 MeV and +8 MeV.

Single-particle strength is reduced by about 50% compared to the independent model.

Results contrast with previous knockout reaction findings.

Abstract

Absolute cross sections for the addition of $s$- and $d$-wave neutrons to $^{14}$C and $^{14}$N have been determined simultaneously via the ($d$,$p$) reaction at 10 MeV/u. The difference between the neutron and proton separation energies, $\Delta S$, is around $-20$ MeV for the $^{14}$C$+$$n$ system and $+8$ MeV for $^{14}$N$+$$n$. The population of the $1s_{1/2}$ and $0d_{5/2}$ orbitals for both systems is reduced by a factor of approximately 0.5 compared to the independent single-particle model, or about 0.6 when compared to the shell model. This finding strongly contrasts with results deduced from intermediate-energy knockout reactions between similar nuclei on targets of $^{9}$Be and $^{12}$C. The simultaneous technique used removes many systematic uncertainties.