First non-zero measurement of a nuclear electric dipole moment

Abstract

This paper reports the first non-zero measurement of a nuclear electric dipole moment using a novel method based on the rate of change of a supercurrent first proposed in 2016~\cite{https://doi.org/10.48550/arxiv.1604.02152} and fleshed out in this current paper. The theory, experimental concept and implementation are described in detail. The non-zero nuclear electric dipole moment measured with over 1000 hours of data was that of $^{181}$Ta producing a best value $|d_\text{e}^\text{Ta}|=(3.39\pm0.31_\text{stat})\cdot10^{-32}e\cdot\text{cm}$ and $|d_\text{e}^\text{Ta}|=(3.39\pm3.18)\cdot10^{-32}e\cdot\text{cm}>0$ at 99.985\%CL. There is an uncertainty on the value of overall multiplicative parameters such as the self-inductance of the superconducting circuit ($\pm4\%$), the mutual inductance between the SQUID pickup coil and the sample wire ($\pm15\%$), and the magnitude of the solenoid current ($\pm5\%$). An upper-limit was estimated for the control element, $^{207}$Pb, $|d_\text{e}^\text{Pb}|\lesssim1.2\cdot10^{-31}e\cdot\text{cm}$ at 95\%CL.