The Quenched gA in Nuclei and Infrared Fixed Point in QCD

The possible consequence of an infrared (IR) fixed point in QCD for Nf=2, 3 in nuclear matter is discussed. It is shown in terms of d(ilaton)-χ effective field theory (dχEFT) incorporated in a generalized effective field theory implemented with hidden local symmetry and hidden scale symmetry that the superallowed Gamow–Teller transition in the doubly magic-shell nucleus 100Sn recently measured at RIKEN indicates a large anomaly-induced quenching identified as a fundamental renormalization of gA from the free-space value of 1.276 to ≈0.8. Combined with the quenching expected from strong nuclear correlations “snc”, the effective coupling in nuclei gAeff would come to ∼1/2. If this result were reconfirmed, it would impact drastically not only nuclear structure and dense compact-star matter—where gA figures in π-N coupling via the Goldberger-Treiman relation—but also in search for physics Beyond the Standard Model (BSM), e.g., 0νββ decay, where the fourth power of gA figures.