LOOP INTEGRALS, ℛ-FUNCTIONS AND THEIR ANALYTIC CONTINUATION

To determine entirely the resulting functions of one-loop integrals it is necessary to find the correct analytic continuation to all relevant kinematical regions. We argue that this continuation procedure may be performed in a general and mathematical accurate way by using the ℛ-function notation of these integrals. The two- and three-point cases are discussed explicitly in this manner.