Probing Light Dark Particles in Neutrino Scattering Experiments

TL;DR

This work develops a model‑independent EFT framework for neutrino–dark fermion absorption via five Lorentz structures, and applies it to neutrino scattering experiments. By analyzing COHERENT and CONUS+ CEνNS data, it derives hadronic (nucleon) operator limits Λ_{i,N}, finding them weaker than current LHC and SN1987A constraints, with notable isospin‑dependent suppression for IV vector interactions. The study then examines DUNE near‑detector prospects for leptonic (electron) couplings, showing sensitivity to Λ_{i,e} up to ~1 TeV for mχ up to ~100 MeV, surpassing CHARM II and LEP in several channels. The results highlight complementarity between CEνNS and ν–e scattering probes and illustrate how near‑term and future facilities, along with high‑energy colliders, map different regions of the parameter space for neutrino–dark sector interactions. Overall, DUNE ND emerges as a key platform for testing heavy‑mediator EFTs of ν–χ interactions with electrons, while current CEνNS data provide important cross‑checks against non‑hadronic channels and guide interpretations of collider and astrophysical bounds.

Abstract

In this work we investigate the production of a dark fermionic particle $χ$ in the neutrino scattering experiments. In the framework of effective field theory, such process can be induced by the effective four-fermion interactions involving neutrinos, the dark particle $χ$ and standard model particles. In particular, we examine the constraints on the effective couplings from the neutrinos scattering off nuclei in the COHERENT and CONUS+ experiments as well as the prospects at the DUNE near detector from neutrino-electron scattering. It turns out the current COHERENT and CONUS+ constraints on the cutoff scales are less stringent than those from the existing Large Hadron Collider data. However, the DUNE near detector could probe the cutoff scales beyond the existing CHARM II and LEP limits up to roughly 1 TeV, for the dark particle mass up to roughly 50 MeV.

Figures (6)

• Figure 1: Feynman diagrams for the neutrino scattering off nucleus $\nu_\alpha + {\cal N} \to \chi + {\cal N}$ (left) or electron $\nu_\alpha + e \to \chi + e$ (right), induced by the effective couplings in Eq. (\ref{['lagrangian']}).
• Figure 2: Event numbers at the COHERENT experiment (CsI-2021 dataset) for the SM CE$\nu$NS process (black dashed), the NIN (green dashed) and BRN (blue dashed) backgrounds as well as the NP scenarios with the scalar (pink solid), IC (orange solid) or IV (purple solid) vector coupling, as functions of $n_{\rm PE}$. The data with error bars are for the residual events after subtracting the SSB background. The backgrounds are labeled by the dashed lines with shaded regions, while the NP cases are depicted as the solid lines. We have set the parameters $m_\chi = 10\,\mathrm{MeV}$ and $\Lambda = 500\,\mathrm{GeV}$.
• Figure 3: Binned CONUS+ excess spectra as functions of the reconstructed energy $E_{\rm ee}^{\rm reco}$, for the SM CE$\nu$NS process (dashed black line with shaded region), and the NP scenarios with the scalar, IC or IV vector coupling (solid colored lines), as functions of $E_{\rm ee}^{\rm reco}$. The data with error bars are the measured spectrum. We have set the parameters $m_\chi = 5\,\mathrm{MeV}$ and $\Lambda = 500\,\mathrm{GeV}$.
• Figure 4: Expected distributions of the variable $x \equiv E_e\theta_e^2$ for the DUNE ND on-axis configuration with one year of exposure, shown separately for both the neutrino (left) and antineutrino (right) modes. The shaded regions below the dotted lines denote the SM background from $\nu(\bar{\nu})$-$e^-$ elastic scattering and the subdominant backgrounds from CCQE and mis-identified $\pi^{0}$ events. The colored solid lines are for the total events including the NP signal contribution for the five Lorentz structures (scalar, pseudoscalar, vector, axial-vector, and tensor). We have taken the benchmark values of $m_\chi = 10\,\mathrm{MeV}$ and $\Lambda_{i,e} = 650\,\mathrm{GeV}$ for all the NP cases.
• Figure 5: The 90% C.L. limits on the dark particle mass $m_\chi$ and the cutoff scales $\Lambda_{i,N}$ from the current COHERENT (shaded blue) and CONUS+ (shaded green) data, for all the five Lorentz structures of scalar (top left), pseudoscalar (top right), vector (middle left), axial-vector (middle right) and tensor (bottom) couplings. In the middle left panel, the limits for the IV vector couplings are indicated by the regions below the dashed blue and green lines. Also shown are the limits from the LHC mono-jet, mono-$\gamma$ and mono-$Z/W$ data Ma:2024tkt, the FCNC $B$ and $K$ meson decays Liu:2025lbw and the SN1987A observations Lin:2025mez.