Multifarious roles of hidden chiral-scale symmetry:"Quenching" ${g_A}$ in nuclei

TL;DR

This paper explores how hidden chiral-scale symmetry in QCD influences the renormalization of the axial coupling constant $g_A$ in nuclei, shedding light on the long-standing quenching puzzle and its implications for nuclear processes and dense matter.

Contribution

It proposes a novel perspective linking chiral-scale symmetry to $g_A$ quenching and advocates for a systematic chiral-scale EFT to advance nuclear theory.

Findings

Quenched $g_A$ encodes chiral-scale symmetry emergence in QCD.

Scale symmetry breaking affects $g_A$ in nuclei and neutrinoless double beta decays.

Parallel between $g_A$ quenching in dense matter and hadron-quark continuity.

Abstract

I discuss how the axial current coupling constant $g_A$ renormalized in scale symmetric chiral EFT defined at a chiral matching scale impacts on the axial current matrix elements on beta decays in nuclei with and without neutrinos. The "quenched" $g_A$ observed in nuclear superallowed Gamow-Teller transitions, a long-standing puzzle in nuclear physics, is shown to encode the emergence of chiral-scale symmetry hidden in QCD in the vacuum. This enables one to explore how trace-anomaly-induced scale symmetry breaking enters in the renormalized $g_A$ in nuclei applicable to certain non-unique forbidden processes involved in neutrinoless double beta decays. A parallel is made between the roles of chiral-scale symmetry in quenching $g_A$ in highly dense medium and in hadron-quark continuity in the EoS of dense matter in massive compact stars. A systematic chiral-scale EFT, presently lacking in nuclear theory and potentially crucial for the future progress, is suggested as a challenge in the field.