Next-to-next-to-leading-order nucleon parton distributions from a light-cone quark model dressed with its virtual meson cloud

A detailed study of nucleon parton distribution functions is performed within a radiative next-to-next-to-leading-order (NNLO) parton model whose low-scale input is rigidly described by wave functions which include quarks and dressing a meson cloud. The light-front Hamiltonian dynamics fixes the three-quark wave functions, and the meson cloud is introduced by means of high-order Fock components in time-ordered perturbation theory in the infinite momentum frame. Nonstrange as well as strange meson-baryon fluctuations are considered (π, ρ, ω, K, and K∗, together with N, Δ, Λ, and Σ) and the effects on strange and nonstrange parton distributions investigated showing the large effects due to (nonstrange) sea asymmetries and the delicate balance of the strange asymmetry. The nonstrange and the strange components, the valence as well as the gluon distributions, are compared with available experimental data confirming the need of both nonperturbative degrees of freedom and perturbative (NNLO) radiative effects.