Probing light mediators in the radiative emission of neutrino pair

Abstract

We propose a new possibility of using the coherently enhanced neutrino pair emission to probe light-mediator interactions between electron and neutrinos. With typical momentum transfer at the atomic $\mathcal{O}(1$ eV) scale, this process is extremely sensitive for the mediator mass range $\mathcal{O}({10}^{-3}\sim {10}^4$) eV. The sensitivity on the product of couplings with electron ($g^e$ or $y^e$) and neutrinos ($g^{\nu }$ or $y^{\nu }$) can touch down to $|y^e{y}^{\nu }|<{10}^{-9}\sim {10}^{-19}$ for a scalar mediator and $|g^e{g}^{\nu }|<{10}^{-15}\sim {10}^{-26}$ for a vector one, with orders of improvement from the existing constraints.