FLAVOR AND SPIN OF THE PROTON AND THE MESON CLOUD

We present a complete set of formulas for longitudinal momentum distri bution functions (splitting functions) of mesons in the nucleon. It ca n be applied in the framework of the convolution formalism to the deep -inelastic structure functions (quark distributions) of the nucleon vi ewed as a system composed of virtual ''mesons'' and ''baryons''. Pseud oscalar and vector mesons as well as octet and decuplet baryons are in cluded. In contrast to many approaches in the literature the present a pproach ensures charge and momentum conservation by the construction. We present not only spin averaged splitting functions but also helicit y-dependent ones, which can be used to study the spin content of the n ucleon. The cut-off parameters of the underlying form factors for diff erent vertices are determined from high-energy particle production dat a. We find a universal cut-off parameter for processes involving octet baryons, This information allows one to calculate the flavour and spi n content of the nucleon. The value of the Gottfried Sum Rule obtained from our model (S-G = 0.224) nicely agrees with that obtained by the NMC. In addition, we calculate the x-dependence of the (d) over bar - (u) over bar asymmetry and get an impressive agreement with a recent f it of Martin-Stirling-Roberts. The calculated axial coupling constants for semileptonic decays of the octet baryons agree with the experimen tal data already with the SU(6) wave function for the bare nucleon. As a consequence the Bjorken Sum Rule is nicely reproduced, Although we get improvements for the Ellis-Jaffe Sum Rules for the proton and neut ron in comparison to the naive quark model, the MCM is not sufficient to reproduce the experimental data.