High-precision experiments could reveal small previously unseen differences between the behavior of matter and antimatter.
[1][2][3] In loose terms, the SME can be visualized as being constructed from fixed background fields that interact weakly, but differently, with particles and antiparticles.
Factors that determine the behavior include the particle species involved, the electromagnetic, gravitational, and nuclear fields controlling the system.
Furthermore, for any Earth-bound experiment, the rotational and orbital motion of the Earth is important, leading to sidereal and seasonal signals.
For experiments conducted in space, the orbital motion of the craft is an important factor in determining the signals of Lorentz violation that might arise.
The SME generates a modified Dirac equation that breaks Lorentz symmetry for some types of particle motions, but not others.
In tests of Lorentz symmetry, the noninertial nature of the laboratory due to the rotational and orbital motion of the Earth has to be taken into account.
Another approach is to seek sidereal variations, by continuously monitoring the anomaly frequency for just one species of particle over an extended time.
An experiment conducted by the physicist Gerald Gabrielse of Harvard University involved two particles confined in a Penning trap.
The Penning-trap group at the University of Washington, headed by the Nobel Laureate Hans Dehmelt, conducted a search for sidereal variations in the anomaly frequency of a trapped electron.
The results were extracted from an experiment that ran for several weeks, and the analysis required splitting the data into "bins" according to the orientation of the apparatus in the inertial reference frame of the Sun.
The spectral lines of hydrogen have frequencies determined by the energy differences between the quantum-mechanical orbital states of the electron.
Several experimental groups at CERN are working on producing antihydrogen: AEGIS, ALPHA, ASACUSA, ATRAP, and GBAR.
There would also be the possibility of finding instantaneous Lorentz breaking signals when antihydrogen spectra are compared directly with conventional hydrogen spectra In October 2017, the BASE experiment at CERN reported a measurement of the antiproton magnetic moment to a precision of 1.5 parts per billion.
[10][11] It is consistent with the most precise measurement of the proton magnetic moment (also made by BASE in 2014), which supports the hypothesis of CPT symmetry.
[12] In the year 2001, Hughes and collaborators published their results from a search for sidereal signals in the spectrum of muonium, an atom consisting of an electron bound to a negatively charged muon.
Collaboration at the Brookhaven National Laboratory published results after searching for signals of Lorentz violation with muons and antimuons.
In another, they looked for sidereal variations by allocating their data into one-hour "bins" according to the orientation of the Earth relative to the Sun-centered inertial reference frame.
Their results, published in Physical Review Letters in 2008,[14] show no signatures of Lorentz violation at the resolution of the Brookhaven experiment.