Reactor antineutrinos CE$ν$NS on germanium: CONUS+ and TEXONO as a new gateway to SM and BSM physics

Abstract: Coherent elastic neutrino-nucleus scattering (CE$\nu$NS) is a key process for probing Standard Model and beyond the Standard Model (BSM) properties. Following its first detection by the COHERENT collaboration, recent reactor-based experiments provide a unique opportunity to refine our current understanding. In particular, the high-precision data from CONUS+, combined with the strong bounds from TEXONO, not only validate the CE$\nu$NS process at low energies but also provide improved constraints on the weak mixing angle, neutrino electromagnetic properties - including charge radius, millicharge, and magnetic moment - as well as non-standard interactions and light mediators. We also examine the role of elastic neutrino-electron scattering, which gains significance in certain BSM scenarios and allows us to obtain the best limit for the millicharge of the electron neutrinos. By combining reactor and higher-energy spallation neutron source measurements, this work strengthens CE$\nu$NS as a precision tool for testing the Standard Model and beyond.