Bound on Lorentz and $CPT$ violating boost effects for the neutron

Abstract

A search for an annual variation of a daily sidereal modulation of the frequency difference between colocated $^{129}\text{Xe}$ and $^{3}\text{He}$ Zeeman masers sets a stringent limit on boost-dependent Lorentz and $CPT$ violation involving the neutron, consistent with no effect at the level of 150 nHz. In the framework of the general standard-model extension, the present result provides the first clean test for the fermion sector of the symmetry of spacetime under boost transformations at a level of $10^{−27}$ GeV.