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Comparison of ionization rates induced by ${}^{8}$B solar neutrinos in a liquid xenon detector via different SM processes: CE$\nu$NS (grey), the Migdal effect (orange), and elastic neutrino--electron scattering (blue). For CE$\nu$NS, a constant quenching factor $q_{nr} = 0.15$ is assumed to translate nuclear recoil energies into electron-equivalent recoil energies. For comparison, we show in shaded pink the approximate ROI of the recent PANDAX-4T and XENONnT analyses of solar neutrinos \cite{PandaX:2024muv, XENON:2024ijk}. The color gradient highlights the fact that the efficiency function is not constant at the ROI of these experiments, but rather increases with energy. The signal induced by CE$\nu$NS clearly dominates in the ROI of these experiments, but the Migdal and neutrino--electron scattering contributions are non-negligible. Note that here we have not applied any efficiency factors to the expected ionization rates.

Comparison of ionization rates induced by ${}^{8}$B solar neutrinos in a liquid xenon detector via different SM processes: CE$\nu$NS (grey), the Migdal effect (orange), and elastic neutrino--electron scattering (blue). For CE$\nu$NS, we consider a quenching factor of $q_{nr} = 0.15$ (solid lines) and the quenching factor from NEST (dashed lines) \cite{Szydagis_2011}, to translate nuclear recoil energies into electron-equivalent recoil energies. For comparison, we show in shaded pink the approximate ROI of the recent PandaX-4T and XENONnT analyses of solar neutrinos \cite{PandaX:2024muv, XENON:2024ijk}. The color gradient highlights the fact that the efficiency function is not constant at the ROI of these experiments, but rather increases with energy. The signal induced by CE$\nu$NS clearly dominates in the ROI of these experiments, but the Migdal and neutrino--electron scattering contributions are non-negligible. Note that here we have not applied any efficiency factors to the expected ionization rates.

Scattering rates for CE$\nu$NS in the SM (gray), compared to scenarios with a new flavor-universal light scalar (dark red) or vector (light red) mediator. In both cases, we have assumed flavor-universal couplings. We also show the total efficiencies of the PandaX-4T and XENONnT analyses from Refs.~\cite{PandaX:2024muv, XENON:2024ijk} (blue curves / right vertical axis). The plot clearly reveals the enhancement $\propto 1/E_{\rm nr}$ of the scalar-induced scattering processes compared to the SM at low energies, as expected from \cref{eq:xsec-scalar}.

\textbf{Top left:} limits on the mass and couplings of a new scalar mediator (see \cref{eq:L-scalar}), from the requirement that coherent elastic neutrino--nucleus scattering (CE$\nu$NS) mediated by this new particle shall not violate the 90\% C.L.\ constraints from PandaX-4T (light blue) and XENONnT (blue). We show results for both the S1+S2 analysis (solid) and for the S2-only analysis, but find no significant differences in sensitivity. We also show the expected sensitivity of a hypothetical detector with an exposure of 200~tonne yrs (dark blue dotted). The green region is ruled out by measurements of CE$\nu$NS in the cesium iodide (CsI) detectors of COHERENT. We further show upper limits from the CONUS \cite{CONUS:2021dwh} and Dresden-II \cite{Coloma:2022avw} experiments. The parameter region shaded in purple is excluded by Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB) \cite{Huang:2017egl, Ghosh:2024cxi}. \textbf{Top right:} analogous limits on the mass and couplings of a new scalar mediator with couplings to quarks proportional to the quark masses, see \cref{eq:q-mass-dependence}. \textbf{Bottom left:} constraints on CE$\nu$NS mediated by a light vector with interactions given by \cref{eq:L-vector}. In this panel, our results are obtained assuming a negative product of couplings $g_qg_{\nu}$. Our results for positive couplings (when destructive interference with the SM amplitude may take place) can be found in Fig.~\ref{fig:degeneracy_vector}. Compared to scalar mediators, we further show bounds in shaded orange on a leptophobic vector from NA62 \cite{NA62:2019meo} and MiniBoone \cite{MiniBooNE:2017nqe}. Furthermore, the region within the dotted black line is excluded by a combination of beam dump experiments from visible decays of a $Z^{\prime}$ coupled to baryon number, if further assuming $g_q=g_{\nu}$. We obtained these bounds with \texttt{DarkCast} \cite{Ilten:2018crw}, and arise from a combination of $\nu$-CAL \cite{Blumlein:2013cua, Blumlein:2011mv} and NOMAD/PS191 \cite{Gninenko:2011uv} via $\pi^{0} \rightarrow Z^{\prime}\gamma$. These constraints are significantly relaxed for vector mediators which do not couple to electrons at tree-level. \textbf{Bottom right:} constraints on neutrino--electron scattering through a new leptophilic scalar mediator (see \cref{eq:L-leptophilic}) from the PandaX-4T S2-only analysis. We compare to limits from BBN, Borexino, CONUS, COHERENT (CsI), and Dresden-II \cite{Coloma:2022umy,Coloma:2022avw}.

\textbf{Top left:} limits on the mass and couplings of a new scalar mediator (see \cref{eq:L-scalar}), from the requirement that coherent elastic neutrino--nucleus scattering (CE$\nu$NS) mediated by this new particle shall not violate the 90\% C.L.\ constraints from PandaX-4T (light blue) and XENONnT (blue). We show results for both the S1+S2 analysis (solid) and for the S2-only analysis, but find no significant differences in sensitivity. We also show the expected sensitivity of a hypothetical detector with an exposure of 200~tonne yrs (dark blue dotted). The green region is ruled out by measurements of CE$\nu$NS in the cesium iodide (CsI) detectors of COHERENT. We further show upper limits from the CONUS \cite{CONUS:2021dwh} and Dresden-II \cite{Coloma:2022avw} experiments. The parameter region shaded in purple is excluded by Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB) \cite{Huang:2017egl, Ghosh:2024cxi}. \textbf{Top right:} analogous limits on the mass and couplings of a new scalar mediator with couplings to quarks proportional to the quark masses, see \cref{eq:q-mass-dependence}. \textbf{Bottom left:} constraints on CE$\nu$NS mediated by a light vector with interactions given by \cref{eq:L-vector}. In this panel, our results are obtained assuming a negative product of couplings $g_qg_{\nu}$. Our results for positive couplings (when destructive interference with the SM amplitude may take place) can be found in Fig.~\ref{fig:degeneracy_vector}. Compared to scalar mediators, we further show bounds in shaded orange on a leptophobic vector from NA62 \cite{NA62:2019meo} and MiniBoone \cite{MiniBooNE:2017nqe}. Furthermore, the region within the dotted black line is excluded by a combination of beam dump experiments from visible decays of a $Z^{\prime}$ coupled to baryon number, if further assuming $g_q=g_{\nu}$. We obtained these bounds with \texttt{DarkCast} \cite{Ilten:2018crw}, and arise from a combination of $\nu$-CAL \cite{Blumlein:2013cua, Blumlein:2011mv} and NOMAD/PS191 \cite{Gninenko:2011uv} via $\pi^{0} \rightarrow Z^{\prime}\gamma$. These constraints are significantly relaxed for vector mediators which do not couple to electrons at tree-level. \textbf{Bottom right:} constraints on neutrino--electron scattering through a new leptophilic scalar mediator (see \cref{eq:L-leptophilic}) from the PandaX-4T S2-only analysis. We compare to limits from BBN, Borexino, CONUS, COHERENT (CsI), and Dresden-II \cite{Coloma:2022umy,Coloma:2022avw}.

\textbf{Top left:} limits on the mass and couplings of a new scalar mediator (see \cref{eq:L-scalar}), from the requirement that coherent elastic neutrino--nucleus scattering (CE$\nu$NS) mediated by this new particle shall not violate the 90\% C.L.\ constraints from PandaX-4T (light blue) and XENONnT (blue). We show results for both the S1+S2 analysis (solid) and for the S2-only analysis, but find no significant differences in sensitivity. We also show the expected sensitivity of a hypothetical detector with an exposure of 200~tonne yrs (dark blue dotted). The green region is ruled out by measurements of CE$\nu$NS in the cesium iodide (CsI) detectors of COHERENT. We further show upper limits from the CONUS \cite{CONUS:2021dwh} and Dresden-II \cite{Coloma:2022avw} experiments. The parameter region shaded in purple is excluded by Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB) \cite{Huang:2017egl, Ghosh:2024cxi}. \textbf{Top right:} analogous limits on the mass and couplings of a new scalar mediator with couplings to quarks proportional to the quark masses, see \cref{eq:q-mass-dependence}. \textbf{Bottom left:} constraints on CE$\nu$NS mediated by a light vector with interactions given by \cref{eq:L-vector}. In this panel, our results are obtained assuming a negative product of couplings $g_qg_{\nu}$. Our results for positive couplings (when destructive interference with the SM amplitude may take place) can be found in Fig.~\ref{fig:degeneracy_vector}. Compared to scalar mediators, we further show bounds in shaded orange on a leptophobic vector from NA62 \cite{NA62:2019meo} and MiniBoone \cite{MiniBooNE:2017nqe}. Furthermore, the region within the dotted black line is excluded by a combination of beam dump experiments from visible decays of a $Z^{\prime}$ coupled to baryon number, if further assuming $g_q=g_{\nu}$. We obtained these bounds with \texttt{DarkCast} \cite{Ilten:2018crw}, and arise from a combination of $\nu$-CAL \cite{Blumlein:2013cua, Blumlein:2011mv} and NOMAD/PS191 \cite{Gninenko:2011uv} via $\pi^{0} \rightarrow Z^{\prime}\gamma$. These constraints are significantly relaxed for vector mediators which do not couple to electrons at tree-level. \textbf{Bottom right:} constraints on neutrino--electron scattering through a new leptophilic scalar mediator (see \cref{eq:L-leptophilic}) from the PandaX-4T S2-only analysis. We compare to limits from BBN, Borexino, CONUS, COHERENT (CsI), and Dresden-II \cite{Coloma:2022umy,Coloma:2022avw}.

\textbf{Top left:} limits on the mass and couplings of a new scalar mediator (see \cref{eq:L-scalar}), from the requirement that coherent elastic neutrino--nucleus scattering (CE$\nu$NS) mediated by this new particle shall not violate the 90\% C.L.\ constraints from PandaX-4T (light blue) and XENONnT (blue). We show results for both the S1+S2 analysis (solid) and for the S2-only analysis, but find no significant differences in sensitivity. We also show the expected sensitivity of a hypothetical detector with an exposure of 200~tonne yrs (dark blue dotted). The green region is ruled out by measurements of CE$\nu$NS in the cesium iodide (CsI) detectors of COHERENT. We further show upper limits from the CONUS \cite{CONUS:2021dwh} and Dresden-II \cite{Coloma:2022avw} experiments. The parameter region shaded in purple is excluded by Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB) \cite{Huang:2017egl, Ghosh:2024cxi}. \textbf{Top right:} analogous limits on the mass and couplings of a new scalar mediator with couplings to quarks proportional to the quark masses, see \cref{eq:q-mass-dependence}. \textbf{Bottom left:} constraints on CE$\nu$NS mediated by a light vector with interactions given by \cref{eq:L-vector}. In this panel, our results are obtained assuming a negative product of couplings $g_qg_{\nu}$. Our results for positive couplings (when destructive interference with the SM amplitude may take place) can be found in Fig.~\ref{fig:degeneracy_vector}. Compared to scalar mediators, we further show bounds in shaded orange on a leptophobic vector from NA62 \cite{NA62:2019meo} and MiniBoone \cite{MiniBooNE:2017nqe}. Furthermore, the region within the dotted black line is excluded by a combination of beam dump experiments from visible decays of a $Z^{\prime}$ coupled to baryon number, if further assuming $g_q=g_{\nu}$. We obtained these bounds with \texttt{DarkCast} \cite{Ilten:2018crw}, and arise from a combination of $\nu$-CAL \cite{Blumlein:2013cua, Blumlein:2011mv} and NOMAD/PS191 \cite{Gninenko:2011uv} via $\pi^{0} \rightarrow Z^{\prime}\gamma$. These constraints are significantly relaxed for vector mediators which do not couple to electrons at tree-level. \textbf{Bottom right:} constraints on neutrino--electron scattering through a new leptophilic scalar mediator (see \cref{eq:L-leptophilic}) from the PandaX-4T S2-only analysis. We compare to limits from BBN, Borexino, CONUS, COHERENT (CsI), and Dresden-II \cite{Coloma:2022umy,Coloma:2022avw}.

Limits on the couplings versus mass of a new vector mediator at PandaX-4T (S2 only, light blue, dashed; paired analysis, light blue, solid) and XENONnT (blue, solid). These limits are analogous to those shown in the lower left panel in Fig. \ref{fig:limit}, but for the case when destructive interference with the SM is allowed (that is, for $g_\nu g_q > 0$). See main text for further details.

90$\%$ C.L.\ bounds on neutrino NSI via the parameters $\epsilon^{u}_{ee}$ and $\epsilon^{d}_{ee}$ from CE$\nu$NS at COHERENT (CsI). Our bounds (green) are compared to those from Ref.~\cite{COHERENT:2021xmm}(orange).