Feynman parameter for a simple and a squared propagator
= Feynman parameter for a simple and a squared propagator
{c}
{title2=$1/(AB^2)=2\int_0^1(1-x)[xA+(1-x)B]^{-3}dx$}
Differentiate $1/(AB)=\int_0^1[xA+(1-x)B]^{-2}dx$ with respect to $B$ to obtain the displayed identity. The squared denominator supplies the factor $2(1-x)$. Changing the parameter to $1-x$ also changes which denominator carries each weight; its use must be consistent with the shifted <Mass>[mass parameter].