The longitudinal structure function F_L: perturbative QCD and k_T-factorization versus experimental data at fixed W

We use results for the structure functions $F_L$ for a gluon target having nonzero transverse momentum square at order $alpha_s$, obtained in our previous paper, to compare with recent H1 experimental data for $F_L$ at fixwd W values and with collinear GRV predictions at LO and NLO approximation.