Virtual meson cloud of the nucleon and deep inelastic lepton scattering.

Abstract

We address the question of whether the nucleon{close_quote}s nonperturbative antiquark sea can be attributed entirely to its virtual meson cloud and, in essence, whether there exists a smooth transition between hadronic and quark-gluon degrees of freedom. We take into account contributions from {pi} and {ital K} mesons and compare them with the nucleon{close_quote}s antiquark distributions which serve as nonperturbative inputs to the QCD evolution equations. While the agreement of our calculations with data-based parametrizations is satisfactory and scale independent for the flavor-breaking share of the nucleon{close_quote}s antiquark sea, the flavor singlet component is quite poorly described. We find that large meson loop momenta, {parallel}{ital k}{parallel}{approx_equal}0.8 GeV, dominate in the calculation of the nucleon{close_quote}s sea quark distributions in the meson cloud model. This value is close to the scale where perturbative QCD evolution starts, which further indicates the limitations of the applicability of the physical picture of a meson cloud around the nucleon in high-energy processes. {copyright} {ital 1996 The American Physical Society.}