Electron events from the scattering with solar neutrinos in the search of keV scale sterile neutrino dark matter

In a previous work, we showed that it is possible to detect keV scale sterile neutrino dark matter nu(s) in a beta decay experiment using radioactive sources such as T-3 or Ru-106. The signals of this dark matter candidate are monoenergetic electrons produced in the neutrino capture process nu(s) + N' -> N + e(-). These electrons have energy greater than the maximum energy of the electrons produced in the associated decay process N' -> N + e(-) + (nu) over bar (e). Hence, signal electron events are well beyond the end point of the beta decay spectrum and are not polluted by the beta decay process. Another possible background, which is a potential threat to the detection nu(s) dark matter, is the electron event produced by the scattering of solar neutrinos with electrons in target matter. In this article, we study in detail this possible background and discuss its implications for the detection of keV scale sterile neutrino dark matter. In particular, bound state features of electrons in Ru atoms are considered with care in the scattering process when the kinetic energy of the final electron is the same order of magnitude of the binding energy.