New insights into the perturbative structure of electroweak Sudakov logarithms

To match the expected experimental precision at future linear colliders, im proved theoretical predictions beyond next-to-leading order are required. A t the anticipated energy scale of root s = 1 TeV the electroweak virtual co rrections are strongly enhanced by collinear-soft Sudakov logarithms of the form log(2)(s/M-2), With M being the generic mass scale of the W and Z bos ons. By choosing an appropriate gauge, we have developed a formalism to cal culate such corrections for arbitrary electroweak processes. As an example we consider in this letter the process e(+)e(-)-->f (f) over bar and study the perturbative structure of the: electroweak Sudakov logarithms by means of an explicit two-loop calculation. In this way we investigate how the Sta ndard Model, with its mass gap between the photon and Z boson in the neutra l sector, compares to unbroken theories like QED and QCD. In contrast to wh at is known for unbroken theories we find that the Sudakov logarithms are n ot exclusively given by the so-called rainbow diagrams, owing to the mass g ap and the charged-current interactions. in spite of this, we nevertheless observe that the two-loop corrections are consistent with an exponentiation of the one-loop corrections. In this sense the Standard Model behaves like an unbroken theory at high energies. (C) 2000 Published by Elsevier Scienc e B.V.