On the kinematic reconstruction of deep inelastic scattering at HERA

We review and compare the reconstruction methods of the inclusive deep inelastic scattering variables used at HERA. We introduce a new prescription, the sigma (Σ) method, which allows to measure the structure function of the proton F2(x, Q2) in a large kinematic domain, and in particular in the low x-lowQ2 region, with small systematic errors and small radiative corrections. A detailed comparison between the Σ method and the other methods is shown. Extensions of the Σ method are presented. The effect of QED radiation on the kinematic reconstruction and on the structure function measurement is discussed.