Next-to-leading-order contributions to R=σL/σTin QCD

We study the exact relations between $F_L$(x,$Q^2$) and $F_2$(x,$Q^2$) and their moments in QCD. We also obtain the analytic expression which allows the reconstruction of $F_L^{\mathrm{NS}(\mathrm{x}}$,$Q^2$) once $F_2^{\mathrm{NS}(\mathrm{x}}$,$Q^2$) is known up to next-to-leading order (NS denotes nonsinglet). The large-x behavior and the magnitude of the next-to-leading-order corrections to the nonsinglet piece of R(x,$Q^2$) are investigated. We obtain a substantial increment of this contribution with respect to the leading-order result.