New clock comparison searches for Lorentz and CPT violation

We present two new measurements constraining Lorentz and CPT violation using the 129Xe/3He Zeeman maser and atomic hydrogen masers. Experimental investigations of Lorentz and CPT symmetry provide important tests of the framework of the standard model of particle physics and theories of gravity. The two-species 129Xe/3He Zeeman maser bounds violations of CPT and Lorentz symmetry of the neutron at the 10−31 GeV level. Measurements with atomic hydrogen masers provide a clean limit of CPT and Lorentz symmetry violation of the proton at the 10−27 GeV level.