The relevance of the vertex bremsstrahlung photon detection in the νe(νe)e− scattering experiments at low energy

We discuss the size of the νe(νe)e−→νe(νe)e− cross section reduction due to the rejection of the events with a vertex bremsstrahlung photon above a certain energy in the final state. In particular we analyze the effect in experiments designed to detect the low energy νe and νe from a nuclear reactor and from the Sun. We find that such reduction has to be considered in a relatively high statistic reactor experiment, while it is negligible for pp and 7Be solar neutrino detection.