Description
We consider four-dimensional quantum field theories (QFTs) coupled to the background dilaton and graviton fields. The IR effective action of these background fields is fixed by trace anomalies. Using this effective action we compute the dilaton-graviton scattering amplitude. We show that it receives a universal helicity-flipping contribution proportional to (∆c − ∆a) along any RG flow, where ∆c and ∆a are the differences of the UV and IR c- and a-trace anomalies respectively. This allows us to relate (∆c − ∆a) to spinning massive states in the spectrum of the QFT. We test our predictions in simple examples. We discuss possible applications.