Evaluation of two-loop self-energy diagram with three propagators.

Small momentum expansion of the ”sunset” diagram with three different masses is obtained. Coefficients at powers of p2 are evaluated explicitly in terms of dilogarithms and elementary functions. Also some power expansions of ”sunset” diagram in terms of different sets of variables are given. The ”sunset” diagram (see Fig. 1) was the object of investigation in several recent works [1, 2, 3, 4, 5]. Such activity is initiated, certainly, by rather high precision of experimental testing of the standard model that needs sometimes evaluation of two-loop Feynman diagrams for comparison of the theory and experiments. Figure 1: The ”sunset” diagram ∗e-mail address: [email protected]