The contribution of off-shell gluons to the longitudinal structure   function F_L
  We present results for the structure function F_L for a gluon target having nonzero transverse momentum square at order \alpha_s. The results of double convolution (with respect to Bjorken variable x and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with recent experimental data for F_L at low x values and with predictions of other approaches. 
A. V. Kotikov (JINR, Dubna), A. V. Lipatov (MSU, Moscow), N. P. Zotov   (SINP, MSU, Moscow)