Interpreting $W$ mass measurements in the SMEFT

TL;DR

This paper analyzes how $W$ mass measurements at hadron colliders can be interpreted within the SMEFT framework, emphasizing the importance of theoretical uncertainties and proper combination of measurements.

Contribution

It demonstrates that Tevatron $m_W$ measurements are compatible with SMEFT constraints when accounting for theoretical uncertainties in the measurement interpretation.

Findings

Tevatron $m_W$ measurements are consistent with SMEFT constraints.

Pure theoretical uncertainties dominate the interpretation of $m_W$ measurements.

Naive combination of different collider measurements can lead to implicit UV assumptions.

Abstract

Measurements of the $W^\pm$ mass ($m_W$) provide an important consistency check of the Standard Model (SM) and constrain the possibility of physics beyond the SM. Precision measurements of $m_W$ at hadron colliders are inferred from kinematic distributions of transverse variables. We examine how this inference is modified when considering the presence of physics beyond the SM expressed in terms of local contact operators. We show that Tevatron measurements of $m_W$ using transverse variables are transparent and applicable as consistent constraints in the Standard Model Effective Field Theory (SMEFT) with small measurement bias. This means that the leading challenge to interpreting these measurements in the SMEFT is the pure theoretical uncertainty in how these measurements are mapped to Lagrangian parameters. We stress the need to avoid using naive combinations of Tevatron and LEPII measurements of $m_W$ without the introduction of any SMEFT theoretical error to avoid implicit UV assumptions. In a companion paper, we implement our procedure to consistently incorporate $m_W$ measurements into a global fit.