Partonic structure of constituent quark (or{ \it{ valon}}) in the Next-to-Leading Order is used to calculate pion structure function. This is a further demonstration of the finding that the constituent quark structure is universal, and once it is calculated, the Structure of any hadron can be predicted thereafter, using a convolution method, without introducing any new free parameter. The results are compared with the pion structure function from ZEUS Coll. Leading Neutron Production in $e^{ +}p$ collisions at HERA. We found good agreement with the experiment. A resolution for the issue of normalization of the experimental data is suggested. In addition, the proportionality of $F_{ 2}^{ \pi}$ and $F_{ 2}^{ p}$, which have caused confusion in the normalization of ZEUS data is discussed and resolved.
Categories: hep-ph hep-ex