Analytical result for dimensionally regularized massless master double box with one leg off shell

The dimensionally regularized massless double box Feynman diagram with powers of propagators equal to one, one leg off the mass shell, i.e. with nonzero q(2) = p(1)(2), and three legs on shell, p(i)(2) = 0, i = 2, 3, 4, is analytically calculated for general values of q(2) and the Mandelstam variables a and t. An explicit result is expressed through (generalized) polylogarithms, up to the fourth order, dependent on rational combinations of q(2), s and t, and a one-dimensional integral with a simple integrand consisting of logarithms and dilogarithms. (C) 2000 Elsevier Science B.V. All rights reserved.