On the Validity of the Effective Field Theory Approach to SM Precision Tests

TL;DR

This paper examines the conditions under which effective field theories (EFTs) reliably describe physics beyond the Standard Model, emphasizing the importance of reporting experimental constraints as functions of energy scales for broad interpretability.

Contribution

It provides a practical framework for assessing EFT validity and a prescription for reporting experimental results to maximize their theoretical utility.

Findings

EFT validity depends on energy scale and UV dynamics assumptions.

Reporting constraints as functions of kinematic variables enhances interpretability.

A practical method for assessing EFT truncation errors is proposed.

Abstract

We discuss the conditions for an effective field theory (EFT) to give an adequate low-energy description of an underlying physics beyond the Standard Model (SM). Starting from the EFT where the SM is extended by dimension-6 operators, experimental data can be used without further assumptions to measure (or set limits on) the EFT parameters. The interpretation of these results requires instead a set of broad assumptions (e.g. power counting rules) on the UV dynamics. This allows one to establish, in a bottom-up approach, the validity range of the EFT description, and to assess the error associated with the truncation of the EFT series. We give a practical prescription on how experimental results could be reported, so that they admit a maximally broad range of theoretical interpretations. Namely, the experimental constraints on dimension-6 operators should be reported as functions of the kinematic variables that set the relevant energy scale of the studied process. This is especially important for hadron collider experiments where collisions probe a wide range of energy scales.