Progress in Tests of Fundamental Physics Using a Helium-3 and Xenon-129 Zeeman Maser

We report on improved operation and understanding of the 3He and 129Xe Zeeman maser and its use in testing new theories in fundamental physics. The 3He and 129Xe Zeeman maser can make differential measurements of magnetic field versus new spin dependent forces that couple to the neutron, as 3He and 129Xe have nuclear gyromagnetic ratios that differ by a factor of ∼2.75, but whose spin-1/2 nuclear moments are due almost entirely to unpaired neutrons. Specifically, we evaluate the performance of the 3He and 129Xe maser in terms of searches for Lorentz and CPT symmetry breaking background fields to the universe described by the Standard Model Extension of Kostelecky and coworkers [1] and for placing limits on anomalous spin-spin coupling between neutrons such as those due to spin dependent forces mediated by the proposed axion particle [2]. The 3He and 129Xe maser has previously been used to place a limit on the coupling of the neutron to Lorentz and CPT symmetry violating fields at the level of 10-31 GeV (50 nHz in the 3He Zeeman frequency). Improvements we have made to the maser system have increased our sensitivity by almost a factor of four and we believe reasonable future upgrades could lead to a further order of magnitude improvement. In this work we have also measured the nuclear Zeeman frequencies of a 3He and 129Xe maser while modulating the nuclear spin polarization of a nearby 3He ensemble in a separate glass cell. We place limits on the coupling strength of neutron spin-spin interactions mediated by light pseudoscalar particles like the axion ( gpgp/(4pihc)) at the 3 x 10-7 level for interaction ranges longer than about 40 cm.