TaO$^+$, a Candidate Molecular Ion in Search of Physics Beyond the Standard Model

TL;DR

The paper proposes TaO$^+$ as a promising molecular ion for detecting physics beyond the standard model, highlighting its significant ${ m{P,T}}$-odd enhancements and favorable properties for experimental searches of electric dipole moments.

Contribution

It introduces TaO$^+$ as a new candidate with advantageous ${ m{P,T}}$-odd properties and reduced systematic error susceptibility compared to similar systems.

Findings

High effective electric field $E_{eff}$ of 20.2 GV/cm.

Significant nucleon-electron scalar-pseudoscalar interaction constant $W_S$ of 17.7 kHz.

Smaller G-tensor component reduces systematic errors.

Abstract

The TaO$^+$ molecular ion is proposed as a candidate system for detecting signatures of charge parity (${\cal{CP}}$) violating physics beyond the standard model of elementary particles. The electron electric dipole moment (EDM) effective electric field $E_{\text{eff}} = 20.2 \left[\frac{\rm GV}{\rm cm}\right]$, the nucleon-electron scalar-pseudoscalar (ne-SPS) interaction constant $W_{S} = 17.7$ [kHz] and the nuclear magnetic quadrupole interaction constant $W_M = 0.45$ [$\frac{10^{33} {\text{Hz}}}{e\, {\text{cm}}^2}$] are found to be sizeable ${\cal{P,T}}$-odd enhancements. The ratio of the leptonic and semi-leptonic enhancements differs strongly from the one for the ThO system which may provide improved limits on the electron EDM, $d_e$, and the SPS coupling constant, $C_S$. TaO$^+$ is found to have a ${^3\Delta_1}$ electronic ground state like the previously proposed ThF$^+$ molecular ion, but an order of magnitude smaller parallel G-tensor component which makes it less vulnerable to systematic errors in experiment.