Constraints onT-odd,P-even interactions from electric dipole moments, reexamined

Abstract

We construct the relationship between nonrenormalizable, effective, time-reversal violating (TV) parity-conserving (PC) interactions of quarks and gauge bosons and various low-energy TVPC and TV parity-violating (PV) observables. Using effective field theory methods, we delineate the scenarious under which experimental limits on permanent electric dipole moments (EDM's) of the electron, neutron, and neutral atoms as well as limits on TVPC observables provide the most stringent bounds on new TVPC interactions. Under scenarios in which parity invariance is restored at short distances, the one-loop EDM of elementary fermions generate the most severe constraints. The limits derived from the atomic EDM of 199 Hg are considerably weaker. When parity symmetry remains broken at short distances, direct TVPC search limits provide the least ambiguous bounds. The direct limits follow from TVPC interactions between two quarks.

Vector analyzing power in elastic electron-proton scattering

“…As discussed in Refs. [4,5], direct searches are most relevant in symmetry-breaking scenarios wherein parity is broken at or above the scale for the breakdown of T. Existing direct searches imply that ␣ T Շ fewϫ 10 −3 , where ␣ T is the ratio of a typical T-odd, P-even nuclear matrix element to those of the residual strong interaction. When translated into bounds on generic, dimension-7 operator coefficients C 7 [under the normalization of Eq.…”

“…Working to second order in p / M, we obtain all contributions to A n that arise uniquely from one-loop, two-photon exchange amplitudes and obtain a prediction that is free from any unknown parameters. We also write down the leading, nonrenormalizable T-odd, P-even eepp operators whose intereference with M ␥ can generate a nonzero VAP and show that they contribute at O͑p / M͒ 4 . We find that inclusion of all one-loop effects through O͑p / M͒ 2 in M ␥␥ as well as all terms in M ␥ through this order is sufficient to resolve the disagreement between the SAMPLE result and the simplest potential scattering predictions.…”

“…Searches for such interactions have been carried out in neutron and nuclear ␤-decay as well as nuclear ␥-decays [1][2][3]. Indirect constraints may also be obtained from limits on the permanent electric dipole moments of neutral atoms under various assumptions regarding the pattern of symmetry-breaking [4][5][6][7][8]. The sensitivity of direct searches for T-odd, P-even interactions is generally limited by the presence of QED "final state interactions" (FSIs) that break the T-symmetry between initial and final states and give rise to nonvanishing T-odd, P-even observables.…”

Low energy tests of the weak interaction

“…As noted in Ref. [295], EDMs provide unambiguous constraints on TVPC interactions only when one assumes that the scale at which P is broken is well below that of the breakdown of T. Then the lepton and neutron EDMs are considerably more sensitive to these effects than the EDMs of neutral atoms such as 199 Hg [296]. Thus, were one to observe non-vanishing EDMs in leptons and the neutron but not in neutral atoms, one might favor an explanation in terms of TVPC interactions.…”

Physics and outlook for rare, all-neutral Eta decays

“…The magnitude of such a new interaction is indirectly constrained by EDM measurements since a CV,P,CPV interaction could mix with the usual weak interaction to yield C,PV,CPV. However, these indirect constraints from EDMs turn out to be hierarchically ambiguous [11], so direct constraints on C violation with P conservation with sensitivity as close as possible to the weak scale would be very interesting.…”