The massless non-adjacent double off-shell scalar box integral — branch cut structure and all-order epsilon expansion

We generalize the result of our recent paper on massless single off-shell scalar box integral to case two non-adjacent end points off light cone. An analytic in $d=4-2\varepsilon$ dimensions is established terms four Gauss hypergeometric ${_2}\mathrm{F}_1$ functions respectively their single-valued counterparts. This allows for an explicit splitting real and imaginary parts, as well all-order $\varepsilon$-expansion polylogarithms.