Precision Tests of SM and new physics with the COHERENT Ge-mini and TEXONO data

Abstract

A comprehensive numerical analysis of the latest germanium based CE$\nu$NS data from the COHERENT Ge-mini and TEXONO experiments has been conducted to test the Standard Model (SM) and search for new physics. By combining CE$\nu$NS and E$\nu$NS signals with a consistent treatment of detector effects and systematic uncertainties, we obtain a low energy determination of the weak mixing angle from COHERENT Ge-mini, in agreement with the SM prediction. We derive novel constraints on neutrino electromagnetic properties, including the magnetic moment, millicharge, charge radius, and anapole moment, with TEXONO providing particularly competitive bounds. Inclusion of E$\nu$NS, significantly improves the sensitivity to the neutrino millicharge by up to three orders of magnitude. We also investigated light scalar and vector mediators, finding striking complementarity between reactor and stopped pion sources across different mediator mass regimes. Finally, we put bounds on sterile neutral leptons production through transition dipole, scalar, and vector portals, probing masses from the sub MeV to tens of MeV scale. Our results demonstrate that current germanium based CE$\nu$NS experiments provide a powerful low energy laboratory for precision electroweak tests and complementary probes of a broad class of physics beyond the SM.