Abstract
Interferences are not positive-definite and therefore they can change sign over the phase space. If the contributions of the regions where the interference is positive and negative nearly cancel each other, interference effects are hard to measure. In this paper, we propose a method to quantify the ability of an observable to separate an interference positive and negative contributions and therefore to revive the interference effects in measurements. We apply this method to the anomalous gluon operator in the SMEFT for which the interference suppression is well-known. We show that we can get, for the first time, constraints on its coefficient using the interference only similar to those obtained by including the square of the new physics amplitude.
Highlights
The Standard Model effective field theory (SMEFT) explores the deviations in SM couplings due to interactions among Standard Model (SM) particles and new states, too heavy to be produced at the LHC or any other considered experiment
We used the sign of the measurable matrix element as a tool to revive the interference and to quantify the efficiency of differential distributions to separate negatively and positively contributing regions of the phase space
We used it to find efficient distributions to look for the interference effect of anomalous gluon interactions, as predicted by the SMEFT, and to put on the corresponding operators, for the first time, constraints which are dominated by the leading [OðΛ−2Þ] interference and not by the OðΛ−4Þ term, coming from the new physics amplitude squared
Summary
The Standard Model effective field theory (SMEFT) explores the deviations in SM couplings due to interactions among Standard Model (SM) particles and new states, too heavy to be produced at the LHC or any other considered experiment Those new states affect the interactions between the SM particles and accurate measurements of their strengths should, reveal or constrain the presence of new physics. We will focus on a single operator in the rest of the paper, the method is generic and can be applied for any interference suppressed by a sign flip in the phase space, including interference unrelated to the SMEFT. Another obvious application in the SMEFT is the CP-violating operators [4]. Their interference do not contribute to the total cross section of C-even processes by symmetry, but they can probed using CP-violating observables
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