DOUBLE BUBBLE CORRECTIONS TO HEAVY-QUARK PRODUCTION

Second order Omicron(alpha(s)(2)) corrections to the heavy quark produ ction cross-section due to massless quarks and coloured scalars are ca lculated for all energies above threshold. Based on the method introdu ced in this letter also the gauge non-invariant second order correctio ns due to the pure gluonic self-energy insertion and a certain class o f Omicron(alpha(s)(3)) and Omicron(alpha(s)(4)) corrections are determ ined. For the special choice of the gauge parameter, xi=4, the leading threshold and high energy behaviour of the pure second order gluonic corrections to the cross-section are governed by the gluonic self-ener gy insertion.