Resolve charge-symmetry breaking in A=4 hypernuclei splittings within NLEFT

Determine the charge-symmetry breaking contribution that differentiates the J=0+–J=1+ level splittings of the A=4 hypernuclei Λ4H and Λ4He within the Nuclear Lattice Effective Field Theory framework used here, so that the calculation can resolve this effect rather than averaging the two splittings.

Background

In the fitting strategy for the three-baryon ΛNN forces, the authors use the A=4 and A=5 systems as constraints. For the A=4 sector, experimental studies show a small but measurable charge-symmetry breaking effect in the splitting between the ground (0+) and excited (1+) states of Λ4H and Λ4He.

Because the present NLEFT setup does not include explicit mechanisms (e.g., Λ–Σ0 conversion and other charge-symmetry breaking ingredients) necessary to resolve this difference, the authors average the two splittings. A calculation that can resolve this effect would enable a sharper determination of spin-dependent ΛNN interactions and improve predictive power in light hypernuclei.