Many-body Fock sectors in Wick-Cutkosky model

In the model where two massive scalar particles interact by the ladder exchanges of massless scalar particles (Wick-Cutkosky model), we study in light-front dynamics the contributions of different Fock sectors (with increasing number of exchanged particles) to full normalization integral and electromagnetic form factor. It turns out that two-body sector always dominates. At small coupling constant α ≪ 1, its contribution is close to 100%. It decreases with increase of α. For maximal value α = 2π, corresponding to the zero bound state mass, two-body sector contributes to the normalization integral 64%, whereas the three-body contribution is 26% and the sum of all higher contributions from fourto infinite-body sectors is 10%. Contributions to the form factor from different Fock sectors fall off faster for asymptotically large Q2, when the number of particles in the Fock sectors becomes larger. So, asymptotic behavior of the form factor is determined by the two-body Fock sector.