Simone Li Muli (UTK): Emergent Wigner SU(4) Symmetry in Light Nuclei and its Implications for Electroweak Responses Beyond CVC

Monday Sep 28, 2026, 1:50 PM → 2:40 PM US/Eastern

604 (Nielsen)

Wigner's SU(4) spin-isospin symmetry was introduced nearly a century ago to describe nuclear structure and reactions, but was long presumed to be severely broken by spin-orbit and tensor forces. Modern ab initio chiral effective field theory calculations reveal, however, a striking emergent SU(4) purity (≥ 90%) in light nuclei (A ≤ 8).

 

At low momentum transfer, the one-body axial-current operator acts approximately as an SU(4) generator within supermultiplets, while two-body currents connect different representations. These selection rules explain longstanding puzzles in the convergence of chiral effective field theory calculations, including the anomalously large two-body axial contributions in A=8 β-decays.

 

Furthermore, in this seminar I will show that Gamow–Teller, spin-magnetic dipole, and isovector charge operators all belong to the same SU(4) adjoint multiplet, connecting axial, vector magnetic, and isovector vector-charge responses within a single algebraic framework. In both A=6 and A=3 systems, symmetry-projected form factors for these three channels exhibit sub-percent shape agreement up to q ≈ 200 MeV/c. This opens a route beyond the Conserved Vector Current (CVC) hypothesis: using precisely measured electromagnetic and charge observables to constrain axial matrix elements. I will present these recent results and discuss the outlook for precision calibration of nuclear responses relevant to β-decay.