Search for new physics with reactor neutrino at Kuo-Sheng neutrino laboratory

The observation of coherent elastic neutrino nucleus scattering by the COHERENT collaboration alongside a positive hint from the DRESDEN−II experiment propelled the study of neutrino physics beyond the Standard Model. In the current work we have explored the light mediator models scenario, along with the neutrino non-standard interactions. Apart from a very good sensitivity to study these physics scenarios, reactor neutrinos provide the benefit of working in the fully coherent region due to their abundant low energy flux. The analyzed data set in the present work comprised of 124.2(70.3) kg day reactor ON(OFF) exposure collected at Kuo-Sheng neutrino laboratory with high purity n-type point Germanium detector. To assess the potential influence of the quenching factor on the limits obtained, we varied the parameter k in the Lindhard model within three scenarios: conservative (0.157), intermediate (0.200), and optimistic (0.260). These choices encompass a range of currently favored values. In the absence of any discernible excess at low energy in the measured spectrum for the considered physics scenarios, we have established competitive limits with the contemporary experiments specifically focused to search for coherent elastic neutrino nucleus scattering.