Measuring Antimatter Gravity with Muonium

TL;DR

This paper proposes a novel experimental approach to measure the gravitational acceleration of antimatter using muonium and atom interferometry, potentially providing groundbreaking insights into fundamental physics.

Contribution

It introduces a new method employing a monoenergetic muonium beam and nanofabricated interferometers to measure antimatter gravity with high precision.

Findings

A 10% measurement of antimatter gravity is feasible within months.

A 1% or better measurement could be achieved with extended exposure.

This approach could be the first to measure gravity of leptonic and second-generation matter.

Abstract

The gravitational acceleration of antimatter, $\bar{g}$, has never been directly measured and could bear importantly on our understanding of gravity, the possible existence of a fifth force, and the nature and early history of the universe. Only two avenues for such a measurement appear to be feasible: antihydrogen and muonium. The muonium measurement requires a novel, monoenergetic, low-velocity, horizontal muonium beam directed at an atom interferometer. The precision three-grating interferometer can be produced in silicon nitride or ultrananocrystalline diamond using state-of-the-art nanofabrication. The required precision alignment and calibration at the picometer level also appear to be feasible. With 100 nm grating pitch, a 10% measurement of $\bar{g}$ can be made using some months of surface-muon beam time, and a 1% or better measurement with a correspondingly larger exposure. This could constitute the first gravitational measurement of leptonic matter, of 2nd-generation matter and, possibly, the first measurement of the gravitational acceleration of antimatter.