A limit on the anisotropy of the one-way maximum attainable speed of the electron
We report here the first experimental result for the anisotropy of the one-way maximum attainable speed of the electron, $\vec{Δc_{1,e}}$, obtained via the study of a sidereal time dependence of a difference between the electron and positron beam momenta in the CESR storage ring at Cornell University. At 95 percent confidence, an upper limit for the component of $Δ\vec {c}_{1,e}/c$ perpendicular to Earth's rotational axis is found to be $5.5 \times 10^{-15}$.
hep-ex↗