New method for fitting coefficients in standard model effective theory

TL;DR

This paper introduces a singular-value decomposition approach for analyzing Wilson coefficients in SMEFT, offering new insights into experimental sensitivities and potential computational benefits over traditional methods.

Contribution

It presents an alternative SVD-based method for principal-component analysis of SMEFT coefficients, highlighting advantages over Fisher-information techniques and demonstrating its application to top-quark decay.

Findings

SVD method reveals sensitivities not seen with Fisher information.

Application to top-quark decay illustrates the method's effectiveness.

Outline of iterative procedure for dimension-8 SMEFT coefficients.

Abstract

We present an alternative method for carrying out a principal-component analysis of Wilson coefficients in standard model effective field theory (SMEFT). The method is based on singular-value decomposition (SVD). The SVD method provides information about the sensitivity of experimental observables to physics beyond the standard model that is not accessible in the Fisher-information method. In principle, the SVD method can also have computational advantages over diagonalization of the Fisher information matrix. We demonstrate the SVD method by applying it to the dimension-6 coefficients for the process of top-quark decay to a $b$ quark and a $W$ boson and use this example to illustrate some pitfalls in widely used fitting procedures. We also outline an iterative procedure for applying the SVD method to dimension-8 SMEFT coefficients.