Correlating uncertainties in global analyses within SMEFT matters

TL;DR

This paper examines how correlations between uncertainties affect SMEFT analyses across multiple experiments, revealing that neglecting correlations can hide potential signs of new physics in future collider data.

Contribution

It provides a model-independent analysis of top-quark data from various colliders, highlighting the importance of correlations in interpreting SMEFT fits and potential new physics signals.

Findings

Ignoring correlations aligns with the Standard Model.

Including correlations suggests possible new physics signals.

Higher order SMEFT corrections are subleading uncertainties.

Abstract

We investigate the impact of correlations between (theoretical and experimental) uncertainties on multi-experiment, multi-observable analyses within the Standard Model Effective Field Theory (SMEFT). To do so, we perform a model-independent analysis of $t$-channel single top-quark production and top-quark decay data from ATLAS, CMS, CDF and D0. We show quantitatively how the fit changes when different experimental or theoretical correlations are assumed. Scaling down statistical uncertainties according to the luminosities of future colliders with $300 \, {\rm fb}^{-1}$ and higher, we find that this effect becomes a matter of life and death: assuming no correlations returns a fit in agreement with the Standard Model while a 'best guess'-ansatz taking into account correlations would observe new physics. At the same time, modelling the impact of higher order SMEFT-corrections the latter turn out to be a subleading source of uncertainty only.