Parity Nonconservation in Rb and Sr$^+$ due to Low-Mass Vector Boson

TL;DR

This paper calculates parity non-conserving transition amplitudes in Rb and Sr$^+$, exploring effects of a hypothetical low-mass $Z'$-boson and advantages of using lighter atoms for new physics searches.

Contribution

It provides detailed calculations of PNC effects in light atoms, emphasizing their potential for detecting new interactions like a low-mass $Z'$-boson.

Findings

PNC effects increase rapidly with decreasing nuclear charge Z.

Lighter atoms offer higher accuracy for interpreting PNC experiments.

Potential to detect or constrain new physics beyond the Standard Model.

Abstract

We calculate the parity non-conserving (PNC) electric-dipole ($E1$) transition amplitudes for the $5s - 6s$ and $5s - 4d_{3/2}$ transitions in Rb and Sr$^+$. Our results include both the nuclear-spin-independent and nuclear-spin-dependent contributions, with particular emphasis on the potential effects of a hypothetical additional $Z'$-boson. We highlight possible advantages of using light atoms in searches for such new interaction. The ratio of the contribution of a low mass $Z'$-boson to the contribution of the Standard model $Z$ -boson to PNC effects increases rapidly (faster than $1/Z^2$) with decreasing nuclear charge $Z$. Another advantage is that theoretical interpretations of experiments in lighter systems may be carried out with a higher accuracy than that in Cs, Ba$^+$, Fr and Ra$^+$.