Analytic two-loop results for selfenergy- and vertex-type diagrams with one non-zero mass

Fleischer, J.; Kotikov, A. V.; Veretin, O. L.

Analytic two-loop results for selfenergy- and vertex-type diagrams with one non-zero mass

Authors

Fleischer, J.

Kotikov, A. V.

Veretin, O. L.

Description

For a large class of two-loop selfenergy- and vertex-type diagrams with only one non-zero mass ($M$) and the vertices also with only one non-zero external momentum squared ($q^2$) the first few expansion coefficients are calculated by the large mass expansion. This allows to `guess' the general structure of these coefficients and to verify them in terms of certain classes of `basis elements', which are essentially harmonic sums. Since for this case with only one non-zero mass the large mass expansion and the Taylor series in terms of $q^2$ are identical, this approach yields analytic expressions of the Taylor coefficients, from which the diagram can be easily evaluated numerically in a large domain of the complex $q^2-$plane by well known methods. It is also possible to sum the Taylor series and present the results in terms of polylogarithms.
LaTeX, 27 pages + 3 ps figures, uses axodraw.sty, some references revisted