A new measurment of the $\bar\nu_{e}e^{-}$ elastic cross section at very low energy

We have built a low background detector, a time projection chamber surrounded by an active anti-Compton, to measure the ν e e − elastic cross section down to the antineutrino energy of 900 keV. With our detector, running at 18 m from the core of a nuclear reactor in Bugey, we could detect reactor antineutrinos by measuring both the energy and the direction of the recoiling electrons. We report here on a first analysis of the data using an automatic scanning procedure. The results we obtain are 1.5 σ higher than the ones predicted by the standard model. (Elsevier)