A Solution to the Quenched ${g_A}$ Problem in Nuclei and Dense Baryonic Matter

TL;DR

This paper proposes that combining scale and chiral symmetries in a Lagrangian explains the effective axial coupling $g_A$ being close to 1 in nuclei and dense matter, challenging traditional explanations and impacting double beta decay physics.

Contribution

It introduces a scale-chiral Lagrangian framework that accounts for the quenching of $g_A$ without relying on meson-exchange currents, suggesting hidden QCD symmetries emerge in dense matter.

Findings

Effective $g_A$ approximates 1 in nuclei and dense matter.

Challenges the meson-exchange current explanation for $g_A$ quenching.

Implications for neutrinoless double beta decay calculations.

Abstract

When scale symmetry is combined with chiral symmetry in a scale-chiral Lagrangian, it can be shown in Fermi-liquid fixed point theory that $g_A^{\rm eff}\approx 1$ in finite nuclei {\it as well as} in dense baryonic matter. This is suggested as a signal for emergence of hidden symmetries of QCD in baryonic matter from low to very high density. This calculation throws doubt on the "first principles" explanation of the quenching of $g_A$ in nuclei with two-body meson-exchange currents. It also has relevance to Gamow-Teller matrix elements in neutrinoless double $\beta$ decay.