Dark Matter EFT Landscape Probed by QUEST-DMC

TL;DR

The paper addresses the challenge of direct detection of sub-GeV dark matter by employing a non-relativistic EFT framework with fourteen operators and a superfluid helium-3 target in the QUEST-DMC experiment. It performs a comprehensive sensitivity projection, including Earth and atmospheric attenuation, and maps NR EFT operators to relativistic DM–nucleon bilinears to facilitate UV-model interpretation. Key contributions include operator-by-operator projected limits, attenuation ceilings, and a detailed relativistic matching that reveals when tensor–scalar and scalar–tensor structures yield stronger constraints than traditional SI/SD forms. The findings demonstrate that QUEST-DMC, especially with SQUID readout, probes previously unexplored regions of the EFT landscape in the sub-GeV regime, providing a versatile bridge between low-energy recoil phenomenology and UV-complete theories.

Abstract

We present the projected sensitivity to non-relativistic Effective Field Theory (EFT) operators for Dark Matter (DM) direct detection using the QUEST-DMC experiment. QUEST-DMC employs superfluid Helium-3 as a target medium and measures energy deposition via nanomechanical resonators with SQUID-based readout to probe DM interactions. The experiment aims to explore new parameter space in the sub-GeV mass range, probing light DM and a broad range of interaction models. We analyse the sensitivity to a complete set of fourteen independent non-relativistic EFT operators, each parameterised by a Wilson coefficient that quantifies the strength of DM interactions with Standard Model particles. For each interaction channel, we determine the corresponding sensitivity ceiling due to attenuation of the DM flux incident on the detector, caused by DM scattering in the Earth and atmosphere. As a key component of this analysis, we provide the mapping between the non-relativistic EFT operators and the relativistic bilinear DM-nucleon interactions, and assess the interaction sensitivity to sub-GeV DM in the QUEST-DMC detector. Our findings demonstrate that QUEST-DMC provides a unique probe of DM interactions, particularly in previously unexplored parameter space for momentum- and velocity-dependent interactions, thereby expanding the search for viable DM candidates beyond traditional weakly interacting massive particles.

Figures (5)

• Figure 1: The QUEST-DMC 90% C.L. limits on the cross-section for velocity and momentum independent operator $\mathcal{O}_1$ and $\mathcal{O}_4$ compared to the existing limits from Xenon 1T S2-only MIGD XENON:2019zpr, CRESST III (LiAlO$_2$) CRESST_2022, LUX (Xe) LUXSD_2016, CDMSlite (Ge) CDMSLite_2018, PandaX-II PandaX-II:2018woa and EDELWEISS EDELWEISS:2019vjv for SD and with existing limits from DarkSide-50 DarkSide-50:2022qzh, XENON1T XENON:2018voc, and EDELWEISS EDELWEISS:2019vjv for SI. The upper limit sensitivity is given with the straight-line (SL) path and the diffusive (Diff) trajectories, depicted in red and black, respectively. The dashed lines correspond to SQUID-based readout systems, while the dotted lines denote conventional readout methods.
• Figure 2: The QUEST-DMC 90% C.L. upper and lower exclusion limits on the cross-section sensitivity region for the non-relativistic EFT operators. The top panels show the SI operators $\mathcal{O}_{8,11}$ (left) and the strongest lower limit for the SI operator $\mathcal{O}_{5}$ (right). The bottom panels display the SD operators $\mathcal{O}_{7,10}$ (left) and $\mathcal{O}_{3,6}$ (right). Operators $\mathcal{O}_{9}$ and $\mathcal{O}_{12}$ are omitted from the plot due to their near-degeneracy with $\mathcal{O}_{10}$ and $\mathcal{O}_{7}$, respectively, in recoil spectra. These operators are numerically indistinguishable within the detector sensitivity range. Similarly, $\mathcal{O}_{13}$ and $\mathcal{O}_{14}$ closely match $\mathcal{O}_{3}$ up to scaling, owing to their shared dependence on both momentum and velocity. The dashed lines stand for the SQUID-based readout systems, and the dotted lines for the conventional readout.
• Figure 3: The left panel shows QUEST-DMC 90% C.L. lower bound on the highest cross-section for operator fifteen sets a threshold beyond which all parameter space is excluded, with no corresponding upper limit. The right panel provides an overview of the collective cross-section range for all analysed operators compared to the existing limits from Xenon 1T S2-only MIGD XENON:2019zpr (For SD) and EDELWEISS EDELWEISS:2019vjv (for SI and SD).
• Figure 4: Projected sensitivity to effective couplings for a range of DM–nucleon interactions classified by the Lorentz bilinears in the relativistic theory, shown for the SQUID-based readout. Each panel corresponds to a different class of nucleon bilinears: scalar (top left), tensor (top right), axialvector (bottom left), and pseudoscalar (bottom right). The colored shaded bands span the region between the lowest point of the projected coupling sensitivity and the highest point of the sensitivity ceiling. The couplings are matched to non-relativistic EFT operators as detailed in Tables \ref{['tab:DM_SI']}–\ref{['tab:DM_tensor']}.
• Figure 5: Effective coupling ranges for DM–nucleon and DM–neutron interactions, grouped by their underlying relativistic bilinear types (SS, TS, AA, etc.) as defined in Tables \ref{['tab:DM_SI']}–\ref{['tab:DM_tensor']}. The couplings represent rescaled Wilson coefficients derived from the QUEST-DMC SQUID-based sensitivity projections shown in Fig. \ref{['fig:EFT_couplings']}. The vertical dashed line with right-pointing arrows indicates the region above the unitarity limit.