Isotopic variation of parity violation in atomic ytterbium

TL;DR

This study measures atomic parity violation across multiple ytterbium isotopes, confirming Standard Model predictions and providing insights into potential new Z' bosons through precise interference experiments.

Contribution

First to observe isotopic variation of atomic parity violation in ytterbium with high precision, supporting Standard Model and constraining new physics.

Findings

Isotopic variation consistent with Standard Model

Achieved 0.5% measurement accuracy for three isotopes

Provided constraints on hypothetical Z' boson properties

Abstract

We report on measurements of atomic parity violation, made on a chain of ytterbium isotopes with mass numbers A=170, 172, 174, and 176. In the experiment, we optically excite the 6s2 1S0 -> 5d6s 3D1 transition in a region of crossed electric and magnetic fields, and observe the interference between the Stark- and weak-interaction-induced transition amplitudes, by making field reversals that change the handedness of the coordinate system. This allows us to determine the ratio of the weak-interaction-induced electric-dipole (E1) transition moment and the Stark-induced E1 moment. Our measurements, which are at the 0.5% level of accuracy for three of the four isotopes measured, allow a definitive observation of the isotopic variation of the weak-interaction effects in an atom, which is found to be consistent with the prediction of the Standard Model. In addition, our measurements provide information about an additional Z' boson.