QCD RELATIONS BETWEEN STRUCTURE FUNCTIONS AT SMALL X

We present very simple non-integral relations between deep inelastic structure functions F_L, F₂ and the gluon distribution at small x based on perturbative QCD which are useful for the phenomenological analysis of data at low x. As an application we extract the deep inelastic scattering cross-sections ratio R = σ_L/σ_T in the range 10⁻⁴ ≤ x ≤ 10⁻² from F₂ HERA data.