Es gilt deutsches Urheberrecht. Das Werk bzw. der Inhalt darf zum eigenen Gebrauch kostenfrei heruntergeladen, konsumiert, gespeichert oder ausgedruckt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. - German copyright law applies. The work or content may be downloaded, consumed, stored or printed for your own use but it may not be distributed via the internet or passed on to external parties.Eden, B.2026-04-012026-04-012025https://oa.tib.eu/renate/handle/123456789/34318https://doi.org/10.34657/33386We advertise intersection theory for generalised hypergeometric functions as a means of evaluating Mellin-Barnes representations. As an example, we study two-parameter representations of the off-shell one- and two-loop box graphs in exactly four-dimensional configuration space. Closing the integration contours for the MB parameters we transform these into double sums. Polygamma functions in the MB representation of the double box and the occurrence of higher poles are taken into account by parametric differentiation. Summing over any one of the counters results into a p+1Fp that we replace by its Euler integral representation. The process can be repeated a second time and results in a two- or four-parameter Euler integral, respectively. We use intersection theory to derive Pfaffian systems of equations on related sets of master integrals and solve for the box and double box integrals reproducing the known expressions. Finally, we use a trick to re-derive the double box from a two-parameter Euler integral. This second computation requires only very little computing resources. Datei-Upload durch TIBeng000 | Informatik, Information und Wissen, allgemeine WerkeReport20 Seiten