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

The dimensionally regularized massless non-planar double box Feynman diagram with powers of propagators equal to one, one leg off the mass shell, i.e., with p(1)(2) = q(2) not equal 0, 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 s, t and u (not necessarily restricted by the physical condition s + t + u = q(2)). An explicit result is expressed through (generalized) polylogarithms, up to the fourth order dependent on rational combinations of q(2), s, t and u, and simple finite two- and three-fold Mellin-Barnes integrals of products of gamma functions which are easily numerically evaluated for arbitrary non-zero values of the arguments. (C) 2001 Published by Elsevier Science B.V.