Constraining nonstandard neutrino interactions at electron colliders

Abstract

The presence of nonstandard neutrino interactions (NSI) has a large effect on the precision measurements at next generation neutrino oscillation experiments. Other type of experiments are needed to constrain the NSI parameter space. We study the constraints on NSI with electrons from current and future $e^+e^-$ collider experiments including Belle II, STCF and CEPC. We find that Belle II and STCF will provide competitive and complementary bounds on electron-type NSI parameters compared to the current global analysis, and strong improvements for the constraints on tau-type NSI. In addition, CEPC alone will impose stringent constraints on the parameter space of NSI with electrons. We find that the degeneracy between the left-handed (vector) and right-handed (axial-vector) NSI parameters can be lifted by combining the data from three different running modes, and the allowed ranges for $|\epsilon_{ee}^{eL}|$ ($|\epsilon_{ee}^{eV}|$) and $|\epsilon_{ee}^{eR}|$ ($|\epsilon_{ee}^{eA}|$) can be constrained to be smaller than 0.002 at CEPC even if both of them are present.