Searching for T-Violating, P-Conserving New Physics with Neutrons

The observance of parity conserving time reversal violation in light quark systems could signal the presence of physics beyond the Standard Model. I discuss the implications of low-energy time reversal tests for the existence of such T-violating, P-conserving (TVPC) interactions. I argue that searches for permanent electric dipole moments (EDM’s) and direct TVPC searches provide complementary information on P-conserving T-violation. EDM searches yield constraints only under the assumption that parity symmetry is restored at the scale ΛTV PC associated with new TVPC physics. If parity remains broken at short distances, direct searches yield the least ambiguous bounds. In the latter case, improving the experimental precision of direct TVPC searches in neutron β-decay and polarized epithermal neutron transmission at the Spallation Neutron Source could yield tighter bounds.