Constraining non-standard neutrino interactions with neutral current events at long-baseline oscillation experiments

Abstract

We explore, for the first time, {\textit{neutral-current}} events at long-baseline experiments to constrain vector and axial-vector neutrino non-standard interactions (NSI) with quarks. We leverage the flavor dependence of NSIs to perform an oscillation analysis in the neutral-current channel. We first introduce a framework to parametrize the effect of NSI on the cross section. Then, as an example, we analyze NOvA neutral-current data which provides significantly improved constraints on the axial-vector NSI parameters ${\epsilon }_{\hat{I}¼\hat{I}¼}^A,{\epsilon }_{\ddot{I}„\ddot{I}„}^A$ and ${\epsilon }_{e\hat{I}¼}^A$. This is highly complementary to constraints from SNO data, which, differently from long-baseline neutral current data, is not sensitive to isospin conserving NSIs ${\epsilon }_u^A={\epsilon }_d^A$. Additionally, we disfavor large values of the diagonal vectorial NSI ${\epsilon }_{\hat{I}¼\hat{I}¼}^V$ and \varepsilon_{ττ}^V$ which originate from the LMA-Dark solution. We also highlight the complementarity between NSI searches at oscillation experiments using charged current and neutral current channels.