Constraining axial non-standard neutrino interactions with MINOS and MINOS+

We show that the neutral current data of the MINOS and MINOS+ experiments can provide information on the axial neutral current non-standard interactions of neutrinos with the $u$ and $d$ quarks; {\it i.e.,} on ${\epsilon }_{\alpha \beta }^{Aq}$. We derive bounds on the $ee$, $e\tau$ and $\tau \tau$ components of these couplings and show that the MINOS(+) bounds on ${\epsilon }_{e\tau }^{Aq}$ and ${\epsilon }_{\tau \tau }^{Aq}$ are currently the world leading ones. The bound on the isospin singlet case, ${\epsilon }_{\tau \tau }^{Au}={\epsilon }_{\tau \tau }^{Ad}$ is of particular interest because while this isospin singlet NSI is theoretically motivated, it was practically unconstrained before these results.