Positivity at 1-loop: bounds on photon and gluon EFTs

Abstract

In this paper, we attempt to derive “positivity” bounds on Photon and Gluon Effective Field Theories (EFTs) at one loop level. While for the Photon case, the one loop amplitude is IR finite and well defined in the forward limit, earlier studies failed to obtain a dispersive bound on dimension-12 operators due to the dependence of the “arc integral” on the artificial low-energy scale. We show that this awkward dependence can be taken care of by analysing the ultra-violet (UV) side of dispersion relation closely. In particular, we derive an IR safe and RG improved bound at 1-loop. Thereafter, we perform a similar analysis on the Gluon EFT, which has additional complications due to ill-defined forward limit and IR divergences at 1-loop. We show that even in this case, one can get a meaningful bound at 1-loop.