QCD analysis of xF₃ structure function data and power correction to α_s

Power corrections both to the strong coupling constant and to the structure function itself are estimated on the basis of the LO, NLO and NNLO QCD analysis of $xF_3$ structure function data. The sign of correction to the coupling constant is found to be negative. The x-shape of a higher twist contribution to the structure function is stable up to NNLO.