Constraints on Millicharged Neutrinos via Analysis of Data from Atomic Ionizations with Germanium Detectors at sub-keV Sensitivities

Department of Physics, Banaras Hindu University, Varanasi 221005, India(Dated: August 4, 2014)With the advent of detectors with sub-keV sensitivities, atomic ionization has been identi ed asa promising avenue to probe possible neutrino electromagnetic properties. The interaction cross-sections induced by millicharged neutrinos are evaluated with the ab-initio multi-con guration rel-ativistic random-phase approximation. There is signi cant enhancement at atomic binding energiescompared to that when the electrons are taken as free particles. Positive signals would distinctlymanifest as peaks at speci c energies with known intensity ratios. Selected reactor neutrino datawith germanium detectors at analysis threshold as low as 300 eV are studied. No such signaturesare observed, and a combined limit on the neutrino charge fraction of j