Constraining axial non-standard interactions of neutrinos with long baseline experiments

TL;DR

This work addresses the possibility that axial non-standard neutrino interactions, encoded in $\epsilon^{Aq}_{\alpha\beta}$, may reveal new physics beyond the standard framework even when vector NSI are constrained. It introduces a UV model with a new $\mathrm{U}(1)$ gauge symmetry that yields $\epsilon^{Au}_{\tau\tau}=\epsilon^{Ad}_{\tau\tau}$ of order unity and analyzes how these axial NSI modify neutral-current neutrino-nucleus scattering across quasi-elastic, resonance, and deep-inelastic regimes, using NuWro cross sections and form-factor inputs. A Cobaya-based MCMC analysis of MINOS(+) NC data provides current bounds, while DUNE projections show potential improvements for $\epsilon^{Aq}_{e\tau}$ and $\epsilon^{Aq}_{\tau\tau}$, though $\epsilon^{Aq}_{ee}$ remains weakly constrained due to SM suppression of electron-flavor channels. The results demonstrate that axial NSI can be probed by long-baseline NC measurements, offering a complementary window to oscillation and CE$\nu$NS constraints and linking to collider and dark-matter phenomenology through the proposed $Z'$ model.

Abstract

Thanks to a number of neutrino oscillation and Coherent Elastic neutrino Nucleus Scattering (CE$ν$NS) experiments, the vector Non-Standard Interactions (NSI) of neutrinos have been well studied and constrained. We show that the long-sought-after new physics may hide in the ``axial" non-standard interactions rather than in the vector NSI. We then show how by studying neutral current scattering events in the detectors of long baseline experiments, MINOS, MINOS$+$ and DUNE, the impact of the axial NSI can be discovered.

Figures (1)

• Figure 1: $\Delta\chi^2_{NC}$ versus the NSI couplings for the isospin singlet (left) and the isospin violating couplings (right) for the $ee$, $e\tau$, and $\tau\tau$ components. In each panel, only one NSI coupling is set nonzero. The horizontal red lines show $\Delta \chi^2_{NC}=2.7$, which corresponds to 90 % C.L. with one degree of freedom. The blue solid lines depict the bounds forecasted for the DUNE experiment assuming zero uncertainty Abbaslu:2023vqk. The dashed (dotted) blue curves show the forecasted bounds for the DUNE experiment with $\sigma_{\epsilon}=0.1$ and $\sigma_{\omega}=0$ (with $\sigma_{\epsilon}=0.1$ and $\sigma_{\omega}=0.02$) Abbaslu:2023vqk. The solid black lines show the bounds based on the MINOS and MINOS+ NC data Abbaslu:2025fwt. The green bands represent the 90 % C.L. bounds obtained by dominated the SNO neutral current data Coloma:2023ixt.