Speaker
Description
We report on ongoing experimental searches for fundamental constant (FC) oscillations which are motivated within models of ultralight scalar dark matter (DM). In one search, the frequency of a bulk acoustic-wave quartz oscillator is compared to the frequency of the ${}^{87}$Rb ground-state hyperfine transition [1], to look for oscillations of the electron mass $m_e$, fine structure constant $\alpha$, and nucleon mass $m_N$, in the frequency range 1.6 mHz-200 Hz (underlying DM particle mass range $6.9\times10^{-18}< m_{\phi} < 8.27\times10^{-13} eVc^{-2}$). In another search carried out in the same frequency range, a radio-frequency electronic transition in ${}^{164}$Dy is probed to look for oscillations in the fine-structure constant [2], exploiting the extreme sensitivity of the transition frequency to changes of this constant. Preliminary results are presented, based on data from a 25-day long quartz-Rb run, and a 12-hr long Dy run. In the absence of detection of FC oscillations, we constrain the DM coupling to $\alpha$, $m_e$ and $m_N$. The constraints on $\alpha$ from the Dy experiment improve on previous results by as many as three orders of magnitude, while the results on the couplings to $m_e$ and $m_N$ from the Rb-quartz experiment improve on previous constraints by an order of magnitude in part of the explored parameter space.
[1] W. M. Campbell et al. PRL 126, 071301 (2021).
[2] K. V. Tilburg et al. PRL 115, 011802 (2015).
