Longitudinal Structure Function $F_{L}$ from Charm Structure Function $F^{c}_{2}$

We predict the effect of the charm structure function on the longitudinal structure function at small x. In NLO analysis we find that the hard Pomeron behavior gives a good description of $F_{L}$ and $F^{c}_{k}$ (k = 2,L) at small x values. We conclude that a direct relation between $F_{L}/F^{c}_{2}$ would provide useful information on how to measure longitudinal structure function at high $Q^{2}$ values. Having checked that this model gives a good description of the data, when compared with other models.