Longitudinal Structure Function $F_L$ from Charm Structure Function $F_2^c$

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 $F_k^c$ (k = 2,L) at small x values. We conclude that a direct relation between $F_L\mathrm{/}{F}_2^c$ 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.