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. 
A.V. Kotikov (TTP, Karlsruhe U.& JINR, Dubna), A.V. Lipatov (Moscow   State U.), N.P. Zotov (SINP, Moscow State U.)