# Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules

## TL;DR

This paper demonstrates that laser-cooled polyatomic molecules with internal degrees of freedom can enable highly sensitive tests of time-reversal symmetry violation, advancing searches for new physics beyond the Standard Model.

## Contribution

It introduces a method to utilize polyatomic molecules with internal degrees of freedom for enhanced symmetry violation measurements, combining laser cooling with desirable molecular features.

## Key findings

- Polyatomic molecules can be fully polarized and serve as internal co-magnetometers.
- Laser cooling of polyatomic molecules with three or more atoms is feasible.
- Enhanced sensitivity in time-reversal symmetry violation searches is achievable.

## Abstract

Precision searches for time-reversal symmetry violating interactions in polar molecules are extremely sensitive probes of high energy physics beyond the Standard Model. To extend the reach of these probes into the PeV regime, long coherence times and large count rates are necessary. Recent advances in laser cooling of polar molecules offer one important tool -- optical trapping. However, the types of molecules that have been laser-cooled so far do not have the highly desirable combination of features for new physics searches, such as the ability to fully polarize and the existence of internal co-magnetometer states. We show that by utilizing the internal degrees of freedom present only in molecules with at least three atoms, these features can be attained simultaneously with molecules that have simple structure and are amenable to laser cooling and trapping.