Tree-level scattering diagram

[David Woodward]

Dear All,

I want to compute a tree-level scattering diagram (see eq. (9), page 6 in http://arxiv.org/abs/hep-th/0211072). The diagram consists of two 2-scalar-1-graviton vertices and one graviton propagator (see the appendix in the aforementioned paper). I want to write a code that contracts the indices and simplifies the expression as much as possible. Could someone please help me?

Best,

David Woodward