Gamow-Teller transitions to 64-Cu measured using the 64-Zn(t,3-He) reaction

TL;DR

This study measured Gamow-Teller transitions to 64-Cu using the 64-Zn(t,3-He) reaction, comparing results with shell-model calculations and existing data, revealing discrepancies with theoretical predictions and implications for stellar electron-capture rates.

Contribution

First measurement of Gamow-Teller strength distribution to 64-Cu via 64-Zn(t,3-He) reaction, highlighting limitations of current shell-model predictions.

Findings

Experimental data showed good consistency.

Shell-model calculations did not reproduce the data.

Electron-capture rates based on theory are significantly lower.

Abstract

The 64-Zn(t,3-He) reaction has been studied using a secondary triton beam of 115 MeV/nucleon to extract the Gamow-Teller transition-strength distribution to 64-Cu. The results were compared with shell-model calculations using the pf-shell effective interactions KB3G and GXPF1A and with existing data from the 64-Zn(d,2-He) reaction. Whereas the experimental results exhibited good consistency, neither of the theoretical predictions managed to reproduce the data. The implications for electron-capture rates during late stellar evolution were investigated. The rates based on the theoretical strength distributions are lower by factors of 3.5-5 compared to the rates based on experimental strength distributions.