paper

The analytic value of the sunrise self-mass with two equal masses and the external invariant equal to the third squared mass

arXiv:hep-ph/0202123 · doi:10.1016/S0550-3213(02)00176-1

Abstract

We consider the two-loop self-mass sunrise amplitude with two equal masses and the external invariant equal to the square of the third mass in the usual -continuous dimensional regularization. We write a second order differential equation for the amplitude in and show as solve it in close analytic form. As a result, all the coefficients of the Laurent expansion in of the amplitude are expressed in terms of harmonic polylogarithms of argument and increasing weight. As a by product, we give the explicit analytic expressions of the value of the amplitude at , corresponding to the on-mass-shell sunrise amplitude in the equal mass case, up to the term included.

11 pages, 2 figures. Added Eq. (5.20) and reference [4]

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