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Search for ultralight axion dark matter in a side-band analysis of a 199Hg free-spin precession signal

by C. Abel, N. J. Ayres, G. Ban, G. Bison, K. Bodek, V. Bondar, E. Chanel, C. B. Crawford, M. Daum, B. Dechenaux, S. Emmenegger, P. Flaux, W. C. Griffith, P. G. Harris, Y. Kermaidic, K. Kirch, S. Komposch, P. A. Koss, J. Krempel, B. Lauss, T. Lefort, O. Naviliat-Cuncic, P. Mohanmurthy, D. Pais, F. M. Piegsa, G. Pignol, M. Rawlik, D. Ries, S. Roccia, D. Rozpedzik, P. Schmidt-Wellenburg, N. Severijns, Y. V. Stadnik, J. A. Thorne, A. Weis, E. Wursten, J. Zejma, G. Zsigmond

This Submission thread is now published as

Submission summary

Authors (as registered SciPost users): Philipp Schmidt-Wellenburg
Submission information
Preprint Link:  (pdf)
Date accepted: 2023-05-24
Date submitted: 2023-04-03 09:44
Submitted by: Schmidt-Wellenburg, Philipp
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
  • Nuclear Physics - Experiment
Approach: Experimental


Ultra-low-mass axions are a viable dark matter candidate and may form a coherently oscillating classical field. Nuclear spins in experiments on Earth might couple to this oscillating axion dark-matter field, when propagating on Earth's trajectory through our Galaxy. This spin coupling resembles an oscillating pseudo-magnetic field which modulates the spin precession of nuclear spins. Here we report on the null result of a demonstration experiment searching for a frequency modulation of the free spin-precession signal of \magHg in a \SI{1}{\micro\tesla} magnetic field. Our search covers the axion mass range $10^{-16}~\textrm{eV} \lesssim m_a \lesssim 10^{-13}~\textrm{eV}$ and achieves a peak sensitivity to the axion-nucleon coupling of $g_{aNN} \approx 3.5 \times 10^{-6}~\textrm{GeV}^{-1}$.

Published as SciPost Phys. 15, 058 (2023)

Author comments upon resubmission

The authors would like to thank the referees for their work and their thoughtful comments.
We acknowledge and partially share the referee's assessment of the strength and weaknesses of the manuscript.
We have modified and changed several passages in the resubmitted version of the manuscript to address all comments and suggestions by the referees.

List of changes

1) Include the recent results in this mass range in Fig. 4 ((
and refer to
A: We agree and have added these references.
We thank the referee for bringing the recent arXiv preprint to our attention.
The results in this preprint replace the limits from old magnetometer data that we previously had in our Figure 4 as shown by the torquoise region.
We have added a reference to this new preprint and updated the torquoise region in our Figure 4.
We have added the Nature Communicantions paper to page 5 of our manuscript where we discuss the effects of stochastic fluctuations (where we previously referred to Ref. [38]).

2) Provide details regarding the mercury vapor. Particularly, what was the vapor pressure?
A: We have provided the typical partial pressure of mercury p_Hg = 4.4E-7mbar in the paragraph on the functioning of the mercuy magnetometer. We calculated the pr using the mean opacity, the light absorption cross section of 2E-13cm^2 and the diameter of the precession chamber.

3) Comment on why the coherent averaging technique was not employed.
A: The sensitivity of our measurements does in fact improve with the total measurement time T as \propto T^{1/2}
rather than \propto T^{1/4} since we operate in the temporally coherent regime (as far as the dark-matter field is concerned).
Our analysis exploits this fact by creating a single time synchronized data trace.
This is because T for us is shorter than the coherence time of the dark-matter field for the
entire dark-matter mass range that we consider.
In future measurements, we intend to take data for a much longer time than the coherence time of the dark-matter field,
in this case the sensitivity will only improve as \propto T^{1/4}.

4) optionally: Change the x-axis in Fig. 3 to be in log-scale, similarly to Fig. 4, so that details of the residuals at
frequencies below 1 Hz can be studied by the reader.
A: We prefer a presentation with a linear scale, as this better shows the residual frequencies above 1Hz.

Submission & Refereeing History

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Resubmission 2212.02403v2 on 3 April 2023

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