The contribution of off-shell gluons to the longitudinal structure function FL

Abstract. We present the results for the structure function $F_{\mathrm{L}}$ for a gluon target having a non-zero transverse momentum square at order $\alpha_{\mathrm{s}}$. The results of a double convolution (with respect to the Bjorken variable x and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with recent experimental data for $F_{\mathrm{L}}$ at low x values and with the predictions of other approaches.