Two-neutrino double beta decay with sterile neutrinos

Usually considered a background for experimental searches the hypothetical neutrinoless double beta decay process, two-neutrino nevertheless provides complementary probe of physics beyond Standard Model. In this paper we investigate how presence sterile neutrino, coupled to Model either via left-handed or right-handed current, affects energy distribution and angular correlation outgoing electrons in decay. We pay particular attention on behaviour at kinematic endpoint estimate current limits active-sterile mixing effective coupling using data as function neutrino mass. also sensitivities future experiments. Our results complement corresponding constraints neutrinos from single measurements 0.1 - 10 MeV mass range.