Description
We propose a new possibility of using the coherently enhanced neutrino pair emission to probe BSM light-mediator interactions between electron and neutrinos. With typical momentum transfer at the atomic $\mathcal O(1\,{\rm eV})$ scale, this process is extremely sensitive for the mediator mass range $\mathcal O(10^{-3}∼10^4)$\,eV. The sensitivity on the product of couplings with electron ($g_e$ or $y_e$) and neutrinos ($g_v$ or $y_ν$) can touch down to $|y_ey_v|<10^{-9}∼10^{−19}$ for a scalar mediator and $|g_eg_ν|<10^{-15}∼10^{−26}$ for a vector one, with orders of improvement from the existing constraints. Being a massless mediator, the photon can also mediate the atomic transition for non-zero neutrino electromagnetic properties. We show the neutrino pair emission can put competitive bounds on the neutrino magnetic moment and electric dipole operators but, most importantly, it can identifying their individual elements which are not possible by existing observations.
