Reviving the interference: framework and proof-of-principle for the anomalous gluon self-interaction in the SMEFT

Abstract

Interferences are not positive-definite and can change sign over the phase space. If the contributions of the regions where they are positive and negative nearly cancel each other, their effects can be hard to measure. In this paper, we propose a method to quantify the ability of an observable to separate these opposite contributions and therefore to revive the interference effects at experiments. We apply this strategy to the anomalous gluon operator in the SMEFT, for which the linear-term suppression is well known. We show that we can get, for the first time, constraints on its coefficient from the interference only that are similar to those from the square of the new-physics amplitude.