Does axial-coupling quenching persist at neutrinoless decay momentum transfers?
In plain words
Simple nuclear models overpredict ordinary beta-decay rates unless the weak axial coupling $g_{\mathrm{A}}$ is reduced by about 25 percent, a correction called quenching. First-principles work explains this with two-nucleon currents and correlations, but whether the same reduction applies to neutrinoless decay, where momenta are about $100\ \mathrm{MeV}/c$, is unknown.
Precise statement
Gamow-Teller quenching at momentum transfer $q \to 0$ (effective $g_{A} \text{ about } 0.75 \text{ times } g_{A} = 1.2754$) was reproduced ab initio by two-body currents and correlations (Gysbers et al., Nature Physics 15, 428, 2019). Determine the effective renormalization of the axial operator at $q \text{ about } 100 \text{ to } 200\,\mathrm{MeV}/c$, relevant to 0nubb, in the same nuclei. Answer: the ratio of $M^{0\nu}$ with and without two-body currents and correlations, with uncertainty.
What would settle it
Ab initio computations of muon capture and forbidden beta decays (which probe $q$ about 100 MeV/c) compared with data, then applied to the 0nubb operator.
Status in the literature
Unverified note
The $q \to 0$ quenching has been considered explained since 2019; its momentum dependence remained open as of 2026.