Fermion observables for Lorentz violation

TL;DR

This paper clarifies the relationship between experimental measurements and theoretical coefficients for Lorentz violation in the fermion sector of the Standard-Model Extension, providing a structured analysis and new limits on electron-sector coefficients.

Contribution

It introduces a block-structured framework for fermion-sector observables and derives thirteen new limits on electron-sector Lorentz violation coefficients.

Findings

Block structure of fermion observables clarified

Decoupling of c coefficients identified

Thirteen new limits on electron-sector coefficients derived

Abstract

The relationship between experimental observables for Lorentz violation in the fermion sector and the coefficients for Lorentz violation appearing in the lagrangian density is investigated in the minimal Standard-Model Extension. The definitions of the 44 fermion-sector observables, called the tilde coefficients, are shown to have a block structure. The c coefficients decouple from all the others, have six subspaces of dimension 1, and one of dimension 3. The remaining tilde coefficients form eight blocks, one of dimension 6, one of dimension 2, three of dimension 5, and three of dimension 4. By inverting these definitions, thirteen limits on the electron-sector tilde coefficients are deduced.