# Top Down Electroweak Dipole Operators

## TL;DR

This paper analyzes constraints on the top quark's electric dipole moment derived from electron and nucleon EDM searches, providing current bounds and prospects for future sensitivity improvements.

## Contribution

It derives the relationship between top quark EDM constraints and light fermion EDM measurements, including renormalization effects and future sensitivity projections.

## Key findings

- Current top EDM bound is ~10^{-19} e cm at 1 TeV scale.
- Future electron and nucleon EDM experiments could improve top EDM sensitivity by an order of magnitude.
- Proton EDM searches could further enhance the constraints on the top quark's EDM.

## Abstract

We derive present constraints on, and prospective sensitivity to, the electric dipole moment (EDM) of the top quark ($d_t$) implied by searches for the EDMs of the electron and nucleons. Above the electroweak scale $v$, the $d_t$ arises from two gauge invariant operators generated at a scale $\Lambda \gg v$ that also mix with the light fermion EDMs under renormalization group evolution at two-loop order. Bounds on the EDMs of first generation fermion systems thus imply bounds on $|d_t|$. Working in the leading log-squared approximation, we find that the present upper bound on $|d_t|$ is roughly $10^{-19}$ $e$ cm for $\Lambda = 1$ TeV, except in regions of finely tuned cancellations that allow for $|d_t|$ to be up to fifty times larger. Future $d_e$ and $d_n$ probes may yield an order of magnitude increase in $d_t$ sensitivity, while inclusion of a prospective proton EDM search may lead to an additional increase in reach.