Searching for an Oscillating Massive Scalar Field as a Dark Matter Candidate Using Atomic Hyperfine Frequency Comparisons

Abstract

We use six years of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant, and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed.PACS numbers: 04.50. Kd,04.80.Cc,06.20.Jr,95.35.+d While thoroughly tested [1], the theory of General Relativity (GR) is currently challenged by theoretical considerations and by galactic and cosmological observations. Indeed, the development of a quantum theory of gravitation or of a theory that would unify gravitation with the other fundamental interactions leads to deviations from GR. These modifications are usually characterized by the introduction of new fields in addition to the space-time metric to model the gravitational interaction. For example, string theory generically predicts the existence of new scalar fields (dilaton, moduli, axions). In addition, in the current cosmological paradigm, some galactic and cosmological observations are explained by the introduction of cold Dark Matter (DM) and of Dark Energy. Little is currently known about these two components that constitute the major part of our Universe. They can be interpreted as new types of matter (although they have not been directly detected so far), as a modification of the theory of gravitation or even as a combination of the two.The introduction of nonminimally coupled scalar fields additionally to GR (tensor-scalar theories) generally leads to a space-time dependence of fundamental constants, which can then be searched for by experiments that test the Einstein equivalence principle (EEP) like weak equivalence principle (WEP) tests or tests of local position or Lorentz invariance (LPI and LLI) [1]. In the past, spectroscopy of different atomic transitions has been widely used to carry out such searches, and has set the tightest limits so far on a possible present-day spacetime variation of fundamental constants [2][3][4][5][6][7][8][9][10][11][12][13][14].Such scalar fields could be a candidate for DM and/or dark energy. Different cosmological evolutions of the scalar fields are possible (see e.g. [15,16]). In several scenarios (in particular in the one defined by the action below), a massive scalar field will oscillate at a frequency related to its mass, leading to a corresponding oscillation of fundamental constants (see e.g. [17,18]). Recently atomic spectroscopy of Dy has been used to constrain such oscillations [2] of the fine structure constant α....

Search for light scalar dark matter with atomic gravitational wave detectors

“…Atomic spectroscopy limits at 95% C.L. on oscillations of relative transition energies in isotopes of Dy [10] and in Rb and Cs [11] are also shown. In red, we plot limits from atomic length scale oscillation effects [12]: one derived from terrestrial seismic data [35] and another from a search for monochromatic scalar strain signals [36] in the AURIGA resonant-mass detector [37].…”

“…Also depicted are 95% C.L. constraints from searches for new Yukawa forces that violate/ conserve the equivalence principle ("EP=5F", gray regions) [32][33][34], atomic spectroscopy data in Dy and in Rb=Cs (light and dark purple regions) [10,11], seismic data on the fundamental breathing mode of Earth (red) [35], and a search for acoustic excitations in the AURIGA resonant-mass detector (red band) [36]. Green regions show natural parameter space for a 10-TeV cutoff, and allowed parameter space for the QCD axion.…”

“…We focus on DM with scalar couplings to matter, which causes time variation of fundamental constants such as the electron mass [9]. This type of DM can be searched for using atomic clocks [9][10][11], resonant-mass detectors [12], and accelerometers [13]. Interesting astrophysical signatures in pulsar systems can also arise for minimal [14] and nonminimal [15] couplings to gravity.…”

Spin precession experiments for light axionic dark matter

“…It is interesting to note axions with even lighter masses below 10 −22 eV can also form a partial contribution to the total dark-matter mass density [61,62]. This extreme ultralight dark matter has been the focus of several recent experimental proposals [42][43][44][46][47][48][49][50], but most have focused on scalar dark matter and its couplings. In this paper, we present several experiments that can be modified or created to search for axions at the lightest masses, and evaluate their potential to reach axion couplings several orders of magnitude beyond current astrophysical bounds.…”

Dark Matter with Genuine Spin-2 Fields

“…This is different from usual interactions [17,[23][24][25][26][27][28][29][30][31] since in the scalar or pseudoscalar cases, the structures of the couplings are very different, being proportional to E 2 − B 2 and E · B, respectively. The induced non-trivial polarization correlations and the possible directional and temporal variations of electric charge therefore constitute a distinguishing signature of the scenario.…”