Reviving the interference: framework and proof-of-principle for the anomalous gluon self-interaction in the SMEFT
Celine Degrande, Matteo Maltoni
TL;DR
In SMEFT, interference between the SM and a dimension-6 operator can cancel across phase space, suppressing sensitivity to the linear term in $C_G/Λ^2$. The authors propose a differential-measurement framework that defines the measurable interference $σ^{|meas|}$ and identifies observables—most notably the transverse sphericity $Sph_T$ and transverse thrust—that efficiently separate positive- and negative-interference regions in three-jet production. Their LO studies show that linear-term bounds on $C_G/Λ^2$ from carefully chosen differential distributions can be competitive with bounds from the squared amplitude, with $Sph_T$ achieving efficiencies above 80%. The approach provides a practical, model-agnostic route to probe anomalous gluon self-interactions and can be extended to other BSM scenarios, pending NLO/PS refinements.
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.