Constraining neutrino electromagnetic properties with recent low-energy electron recoil data at dark matter direct detection experiments

TL;DR

This work constrains neutrino electromagnetic properties by analyzing low-energy solar neutrino–electron scattering data from PandaX-4T and XENONnT. The authors compute event rates including SM and EM contributions from the solar flux with flavor oscillations and detector effects, and perform a Poissonian χ² fit to obtain 90% CL limits on the neutrino magnetic moment $μν$, millicharge $qν$, and charge radius $⟨r^2_ν⟩$, in both flavor-dependent and flavor-independent frameworks. The results show that XENONnT provides the strongest bounds (e.g., $μνℓ ≤ 0.72×10^{-11} μ_B$ flavor-independently), with PandaX-4T Run1 significantly improving over Run0, and bounds for $qν$ and $⟨r^2_ν⟩ that are competitive with or surpass several past direct-detection and solar-neutrino limits. Overall, the study demonstrates the power of modern direct-detection experiments to probe beyond-Standard-Model neutrino electromagnetic properties using low-energy electron recoil data.

Abstract

Neutrinos that are elastically scattered off atomic electrons provide a unique opportunity to investigate the Standard Model (SM) and beyond SM physics. In this work, we explore the new physics effects of neutrino electromagnetic properties through elastic neutrino-electron scattering using solar neutrinos at the low energy range of PandaX-4T and XENONnT experiments. The properties of interest include the neutrino magnetic moment, millicharge, and charge radius, all of which are natural consequences of non-zero neutrino masses. We investigate their effects by incorporating each property into the Standard Model (SM) framework, given the measured the solar neutrino flux. By analyzing the latest Run 0 and Run 1 datasets from the PandaX-4T experiment, together with recent results from XENONnT, we derive new constraints on each electromagnetic property of neutrino. We present both flavor-independent results, obtained using a common parameter for all three neutrino flavors, and flavor-dependent results, derived by marginalizing over the three neutrino flavor components. Bounds we obtained are comparable or improved compared to those reported in the previous studies.

Figures (8)

• Figure 1: Feynman diagrams for neutrino-electron scattering via (a) neutral-current (NC) and (b) charge-current (CC) channels in the SM. The index $\ell$ runs for $e,\mu$, and $\tau$ flavor of neutrino.
• Figure 2: Predicted signals of each neutrino electromagnetic property as a function of electron recoil energy for the PandaX-4T (a) Run0 and (b) Run1, and (c) XENONnT. Individual contributions to the E$\nu$ES are shown as filled colored histograms, while their contributions to the total background are shown as empty, outlined histograms in the same colors.
• Figure 3: One-dimensional $\Delta\chi^2$ distributions of neutrino magnetic moment from the analysis of recent data: (a) PandaX-4T Run0, (b) PandaX-4T Run1, and (c) XENONnT. Results are presented for both the flavor-independent effective neutrino magnetic moment and the flavor-dependent cases obtained via marginalization over the three neutrino flavors.
• Figure 4: The $90\%$ CL allowed regions with 2 d.o.f. in the (a) $(\mu_{\nu_e},\mu_{\nu_\mu})$, (b) $(\mu_{\nu_e},\mu_{\nu_\tau})$ and (c) $(\mu_{\nu_\mu},\mu_{\nu_\tau})$ planes, obtained by marginalizing over the remaining neutrino flavor components. The results correspond to the analysis of PandaX-4T-Run0 (blue region), PandaX-4T-Run1 (red region), and XENONnT data (orange region).
• Figure 5: One-dimensional $\Delta\chi^2$ distributions obtained from the analysis of recent data: (a) PandaX-4T Run0, (b) PandaX-4T Run1, and (c) XENONnT. The results are presented for the neutrino millicharge, including both the flavor-independent effective case and the flavor-dependent cases derived through marginalization over the three neutrino flavors.