Perturbative χEFT calculations of the deuteron and triton up to N2LO

Journal article, 2025

We extend previous studies of the deuteron and triton ground-state energies to next-to-next-to-leading order (N2LO) in chiral effective field theory, employing a power counting in which subleading interactions are treated perturbatively. Triton calculations are performed using the no-core shell model, and we demonstrate converged perturbative results for regulator cutoffs up to Lambda approximate to 1200 MeV. We analyze exceptional cutoffs in the 3P0 and 3S1-3D1 nucleon-nucleon channels and find a resulting cutoff dependence in the triton ground-state energy at N2LO. The effect associated with the exceptional cutoff in the 3P0 channel can be mitigated by redefining the leading-order wave function within the freedom allowed by the effective field theory. The same approach applied in the 3S1-3D1 channel remedies the effect of this exceptional cutoff on the ground state energy of the deuteron, but not for the triton.