2026/07/17 by Teng Wang, Serdar Elhatisari, Xu Feng +2
#nucl-th
The 5730-year half-life of 14C, the physical basis of radiocarbon dating, is anomalously long compared to typical nuclear-physics expectations. Its origin has remained a subject of debate for many decades. Here we report an ab initio nuclear lattice effective field theory (NLEFT) calculation of 14C β decay. Using systematically optimized interactions and transition operators consistently derived from chiral effective field theory, We obtain a result consistent with the Gamow-Teller matrix element MGTexp≃ 2× 10-3 measured with the current uncertainty of O(10-2). We first show that chiral interactions and weak currents beyond leading-order are essential for quenching the GT matrix element to the physical value, among which the optimization of three-nucleon forces is indispensable. We then illustrate that the quenching is deeply rooted in the ground-state structure of 14N as found in the nuclear shell model, where the competition between S- and D-wave components exists, sensitive to the interaction employed. The physical 14N ground state is found to be dominated by D-wave configurations, which constitutes the key factor for the quenching. The sensitivity of the decay matrix element to the fine-tuning of low-energy-constants is explored, revealing the prominent role of the 3S1-channel two-nucleon contact force and the one-pion-exchange three-nucleon force. This work eliminates the gap between shell-model and ab initio studies of 14C β decay, provides a valid and straightforward explanation for the anomalous long lifetime of 14C, and turns NLEFT into a practical tool for the systematic study of nuclear transitions.