Reduction of one-loop integrals with higher poles by unitarity cut method

Understand

Unitarity cut method has been proved to be very useful in the computation of one-loop integrals.

• In this paper, we generalize the method to the situation where the powers of propagators in the denominator are larger than one in general.
• We show how to use the trick of differentiation over masses to translate the problem to the integrals where all powers are just one.
• Then by using the unitarity cut method, we can find the wanted reduction coefficients of all basis except the tadpole.