Analytical result for dimensionally regularized massive on-shell planar double box

The dimensionally regularized master planar double box Feynman diagram with four massive and three massless lines, powers of propagators equal to one, all four legs on the mass shell, i.e. with pi2=m2, i=1, 2, 3, 4, is analytically evaluated for general values of m2 and the Mandelstam variables s and t. An explicit result is expressed in terms of polylogarithms, up to the third order, depending on special combinations of m2, s and t. (orig.)