Tests of  fundamental physics with atomic parity violation in ytterbium
This project aims to establish a novel platform for fundamental tests in nuclear and particle physics, based on detecting isotopic variation of parity violation in atomic nuclei.

Atomic probes in tabletop experiments offer a unique approach to testing fundamental physics, complementary to high-energy-physics experiments in large facilities. In particular, atomic parity violation (APV) provides a window into the effects of weak interaction in atoms. Recent observations by our team on how the APV effect varies among a chain of ytterbium (Yb) isotopes motivate the use of this method as a versatile probe of nuclear and particle physics. More specifically, comparing the APV effect in different isotopes of the same atomic species is a sensitive tool to study the distribution of neutrons in the nucleus, which in turn is closely related to the structure and size of neutron stars. The method is also a probe of additional vector bosons, beyond the Standard Model of particle physics. Finally, the study of nuclear-spin-dependent contributions to the APV effect in isotopes with nuclear spin is a sensitive way to investigate intranuclear weak interactions, which are currently poorly understood.

The objective of the YbFUN project is to substantially expand existing approaches to probing isotopic APV variation and to establish the method as a powerful tool at the interdisciplinary junction between atomic, nuclear and particle physics. Towards this goal, we will i) employ high-precision measurements of isotopic variation of the APV effect in Yb to probe the neutron distribution in the Yb nucleus and thus help answer questions regarding the size of neutron-rich nuclei and neutron stars; ii) make use of the isotopic comparison method to explore electron–nucleon interactions mediated by potential additional Z bosons; and iii) undertake studies of spin-dependent APV to advance the fundamental understanding of intranuclear weak forces.