Present and future bounds on non-standard neutrino interactions

We consider Non-Standard neutrino Interactions (NSI), described byfour-fermion operators of the form $(\bar{\nu}_{\alpha} \gamma {\nu}_{\beta})(\bar{f} \gamma f)$, where $f$ is an electron or first generation quark. Weassume these operators are generated at dimension $\geq 8$, so the relatedvertices involving charged leptons, obtained by an SU(2) transformation$\nu_{\delta} \to e_{\delta}$, do not appear at tree level. These relatedvertices necessarily arise at one loop, via $W$ exchange. We catalogue currentconstraints from $\sin^2 \theta_W$ measurements in neutrino scattering, fromatmospheric neutrino observations, from LEP, and from bounds on the relatedcharged lepton operators. We estimate future bounds from comparing KamLAND andsolar neutrino data, and from measuring $\sin^2 \theta_W$ at the near detectorof a neutrino factory. Operators constructed with $\nu_\mu$ and $\nu_e$ shouldnot confuse the determination of oscillation parameters at a $\nu$factory,because the processes we consider are more sensitive than oscillations at thefar detector. For operators involving $\nu_\tau$, we estimate similarsensitivities at the near and far detector.Comment: Erratum added at the end of the documen