Lepton Symmetry Experiment – matter / antimatter symmetry test with electron and positron

Introduction

In modern physics, we are faced with the unsatisfactory situation that the Standard Model (SM), which condenses our current state of knowledge in the form of quantum field theories, despite its spectacular success in the prediction of laboratory results, fails in explaining even the most basic properties of our Universe. This includes the disparity of matter and antimatter and the possible existence of dark matter.

Role of Low Energy Experiments

In the quest to search for answers to these questions, low energy, high precision experiments in ion traps have taken a pivotal role. These experiments allow for precise tests of the charge, parity, and time (CPT) reversal symmetry.

Proposed Experiment

I propose an ambitious, next-generation Penning-trap experiment that will enable us to directly compare the magnetic moments of electron and positron at 14 digits precision.

Experimental Setup

To this end, we will:

1. Simultaneously trap a single positron and an electron in the same trap.
2. Directly compare their spin precession frequencies.

To enable the co-trapping of the oppositely charged particle and antiparticle, we will bind the electron in a hydrogenlike 4He+ ion.

Measurement of Spin Precession

As a result of the binding, the spins of both particles show a slow beat, which can be accurately measured. Any deviation of this beat frequency from the prediction by quantum electrodynamics (QED) reveals a CPT violation.

This way, LSYM will enable a uniquely sensitive comparison of particle and antiparticle charge, mass, and g-factors, thus yielding the most stringent CPT test in the lepton sector.

Development of Novel Apparatus

To this end, we will develop a novel, superconducting Penning trap apparatus, which can be cooled to millikelvin temperatures to largely eliminate black-body radiation.

Techniques and Measurements

Building upon techniques recently pioneered by my group, LSYM will allow the coherent “quantum” measurement of the difference of the spin precession frequencies.

Furthermore, with this toolbox at hand, we will have access to a new class of intriguing measurements, such as an order of magnitude improved determination of the electron atomic mass.