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 $\epsilon^{Aq}_{e\tau}$ and $\epsilon^{Aq}_{\tau\tau}$ are currently the world leading ones. The bound on the isospin singlet case, $\epsilon^{Au}_{\tau\tau}=\epsilon^{Ad}_{\tau\tau}$ is of particular interest because while this isospin singlet NSI is theoretically motivated, it was practically unconstrained before these results.