YbCaF

The universe seems to be made of matter and not antimatter. This is confusing because our best model of particle physics, the Standard Model, contains no processes which could have enabled such a large imbalance between matter and antimatter to develop. To explain the imbalance, there must be new, undiscovered physics which violates combined CP symmetry. If such new physics exists, it is likely hidden at high energies - high enough to evade detection in our most powerful particle colliders, but low enough to have been relevant in the hot early universe where the imbalance developed.

While these hypothetical exotic new particles have masses too high (or coupling constants too low) to be directly detected by current particle collider experiments like the LHC, their existence can also be inferred from their subtle effect on run-of-the-mill, everyday particles. If a quantum field supporting these new particles exists, and it couples to the Standard Model in some way, it will generically induce tiny CP-violating electromagnetic moments in known Standard Model particles. The lowest order examples of such CP-violating moments are electric dipole moments and magnetic quadrupole moments. In this experiment, we are aiming to make a very precise measurment of the magentic quadrupole moment of the Yb-173 nucleus. A non-zero result would reveal new physics, while a null result would rule out a large swathe of parameter space and help guide new theories.

The signal of a nuclear magnetic quadrupole moment is enhanced in quadrupole deformed nuclei (shaped like a rugby ball, or an american football) like Yb-173. The signal is also hugely enhanced by embedding the nucleus in a polar molecule. We aim to build YbCaF molecules for our measurement. The triatomic structure of the molecule provides powerful techniques to reject many of the most important forms of systematic error in these experiments.

To create this very strange molecule, we will separately laser cool Yb atoms and CaF molecules in optical tweezers and then associate them together to create the triatomics. The YbCaF molecules will be produced at ultracold temperatures and confined in optical tweezer traps, an excellent starting point for a precision measurement.