摘要
The exotic singlet fermions χ, with a mass mχ≲50 MeV, could be produced at the coherent elastic neutrino-nucleus scattering (CEνNS) experiments through the νN→χN process. Due to the coherent enhancement, it offers a unique way to study how χ interacts with the Standard Model (SM) sector. Based on the most general dimension-6 effective Lagrangian, we perform a comprehensive study on the relevant interaction between χ and the SM sector. From the current and future COHERENT and future CONUS experiments, we obtain the upper bounds on the Wilson coefficients for the dipole, scalar, vector, and tensor interactions. For mχ below 10 MeV, future CONUS data has the best sensitivity, while for mχ between 10 MeV-50 MeV, the current and future COHERENT bounds dominate. These limits are complementary to those from neutrino oscillation and collider searches. Moreover, the bounds do not depend on the charge conjugation property of χ, nor whether χ is dark matter or not.