New constraints on Lorentz invariance violation from the neutron electric dipole moment

We propose an original test of Lorentz invariance in the interaction between a particle spin and an electromagnetic field and report on a first measurement using ultracold neutrons. We used a high-sensitivity neutron electric dipole moment (nEDM) spectrometer and searched for a direction dependence of an nEDM signal leading to a modulation of its magnitude at periods of 12 and 24 hours. We constrain such a modulation to d12 < 10×10−25e cm and d24 < 14×10−25e cm at 95% C.L. The result translates into a limit on the energy scale for this type of Lorentz violation effect at the level of εLV > 1010 GeV.