ORDER-ALPHA(S)2 QCD CORRECTIONS TO THE DEEP INELASTIC PROTON STRUCTURE FUNCTIONS F(2) AND F(L)

We present the calculation of the order-alpha(s)2 correction to the deep inelastic coefficient functions C(i)(x, Q2) (i = 2, L). Its effect on the behaviour of the proton structure functions F(i)(x, Q2) for fixed target and HERA energies is studied:We investigate the dependence of the O(alpha(s)2) QCD corrected structure functions on the mass factorization scale and the specific parametrization chosen for the parton densities. Also discussed-are the implications of the higher-order QCD corrections for the extraction of the parton densities, in particular the gluon distribution function, from the data. Our analysis reveals that the O(alpha(s)2) contributions to F2(x, Q2) are appreciable and can amount from +10% (large-x region) to -20% (small-x region), depending on the chosen value for Q2 and the parton density set. In the case of F(L)(x, Q2) the corrections in the small-x region can be even larger (about 45%). The large corrections in the region 0.5 < x < 1, which can be attributed to soft-gluon radiation, may explain the difference observed between the combined SLAC-BCDMS data and the fit based on the next-to-leading-log (NLL) approximation for the proton structure function F2(x, Q2).