Gravitational mass of positron from LEP synchrotron losses

TL;DR

This paper derives an indirect bound on the gravitational mass of the positron using LEP synchrotron loss data, supporting the equivalence principle for antimatter without relying on astrophysical assumptions.

Contribution

It provides the first indirect experimental constraint on the gravitational behavior of antimatter, specifically positrons, using collider data.

Findings

Bound of 0.13% on the difference between gravitational and inertial mass of positrons.

Supports the validity of the equivalence principle for antimatter.

No evidence of antimatter gravity being repulsive.

Abstract

General relativity (GR) is the current description of gravity in modern physics. One of the cornerstones of GR, as well as Newton's theory of gravity, is the weak equivalence principle (WEP), stating that the trajectory of a freely falling test body is independent of its internal structure and composition. WEP is known to be valid for the normal matter with a high precision. However, due to the rarity of antimatter and weakness of the gravitational forces, the WEP has never been confirmed for antimatter. The current direct bounds on the ratio between the gravitational and inertial masses of the antihydrogen do not rule out a repulsive nature for the antimatter gravity. Here we establish an indirect bound of 0.13% on the difference between the gravitational and inertial masses of the positron (antielectron) from the analysis of synchrotron losses at the Large Electron-Positron collider (LEP). This serves as a confirmation of the conventional gravitational properties of antimatter without common assumptions such as, e.g., coupling of gravity to virtual particles, dynamics of distant astrophysical sources and the nature of absolute gravitational potentials.