The structure of large logarithmic corrections at small transverse momentum in hadronic collisions

We consider the region of small transverse momenta in the production of hig h-mass systems in hadronic collisions. By using the current knowledge on th e infrared behaviour of tree-level and one-loop QCD amplitudes at O(alpha ( 2)(S)), we analytically compute the general form of the logarithmically-enh anced contributions up to next-to-next-to-leading logarithmic accuracy. By comparing the results with q(T)-resummation formulae we extract the coeffic ients that control the resummation of the large logarithmic contributions f or both quark and gluon channels. Our results show that within the conventi onal resummation formalism the Sudakov form factor is actually process-depe ndent. (C) 2001 Published by Elsevier Science B.V.