Antimatter Free-Fall Experiments and Charge Asymmetry

TL;DR

This paper proposes a high-precision antimatter charge neutrality test using modified free-fall experiments with electric fields and analyzes possible theoretical descriptions of antimatter charge asymmetry.

Contribution

It introduces a novel experimental setup for testing antimatter charge neutrality and explores Lorentz-invariant theoretical models for charge asymmetry.

Findings

Potential to significantly improve limits on antimatter charge asymmetry

Theoretical models involve CPT-breaking operators that preserve Lorentz invariance

Constraints on charge asymmetry parameters are model-independent

Abstract

We propose a method by which one could use modified antimatter gravity experiments in order to perform a high-precision test of antimatter charge neutrality. The proposal is based on the application of a strong, external, vertically oriented electric field during an antimatter free-fall gravity experiment in the gravitational field of the Earth. The proposed experimental setup has the potential to drastically improve the limits on the charge-asymmetry parameter ${\overline \epsilon}_q$ of antimatter. On the theoretical side, we analyze possibilities to describe a putative charge-asymmetry of matter and antimatter, proportional to the parameters $\epsilon_q$ and ${\overline \epsilon}_q$, by Lagrangian methods. We found that such an asymmetry could be described by four-dimensional Lorentz-invariant operators that break CPT without destroying the locality of the field theory. The mechanism involves an interaction Lagrangian with field operators decomposed into particle or antiparticle field contributions. Our Lagrangian is otherwise Lorentz, as well as PT invariant. Constraints to be derived on the parameter ${\overline \epsilon}_q$ do not depend on the assumed theoretical model.