Ab initio approach to the non-perturbative scalar Yukawa model

We report on the first non-perturbative calculation of the scalar Yukawa model in the single-nucleon sector up to four-body Fock sector truncation (one “scalar nucleon” and three “scalar pions”). The light-front Hamiltonian approach with a systematic non-perturbative renormalization is applied. We study the n  -body norms and the electromagnetic form factor. We find that the one- and two-body contributions dominate up to coupling α≈1.7α≈1.7. As we approach the coupling α≈2.2α≈2.2, we discover that the four-body contribution rises rapidly and overtakes the two- and three-body contributions. By comparing with lower sector truncations, we show that the form factor converges with respect to the Fock sector expansion.