Polarized ρ mesons and the asymmetry between Δd̄(x) and Δū(x) in the sea of the nucleon

We present a calculation of the polarized ρ meson cloud in a nucleon using time-ordered perturbation theory in two different variants advocated in the literature. We calculate the induced difference between the distributions Δd̄(x) and Δū(x). We use a recent lattice calculation to motivate an ansatz for the polarized valence quark distribution of the ρ meson. Our calculations show that the two theoretical approaches give vastly different results. We conclude that Δd̄(x)−Δū(x) can be of relevant size with important consequences for the combined fits of polarized distribution functions.