The structure of a dressed quark is utilized to evaluate the structure function of proton and pion. It is found that there is a simple relationship between $F_{ 2}^{ p}$ and $F_{ 2}^{ \pi}$. The ambiguity in the normalization of $F_{ 2}^{ \pi}$ is discussed. Furthermore, the polarization structure function of the constituent (dressed) quark is calculated in the leading order. While, it does produce all the available data on polarized hadronic structure, it requires a significant contribution to the proton spin from the orbital angular momentum.
Categories: hep-ph