The ADAMO project for the dark matter directionality approach

Anisotropic scintillators can offer a unique possibility to exploit the so-called directionality approach to investigate the presence of those Dark Matter (DM) candidates inducing nuclear recoils. Their use can overcome the difficulty of detecting extremely short nuclear recoil tracks. In this paper, we present recent measurements performed on the anisotropic response of a ZnWO4 crystal scintillator to nuclear recoils in the framework of the ADAMO project. The anisotropic features of the ZnWO4 crystal scintillators were initially measured with α particles; those results have also been confirmed by the additional measurements presented here. The experimental nuclear recoil data were obtained using a neutron generator at ENEA-Casaccia and neutron detectors to tag the scattered neutrons; in particular, the quenching factor values for nuclear recoils along different crystallographic axes have been determined for three different neutron scattering angles (i.e. nuclear recoils energies). The anisotropy of the light response for nuclear recoils in the ZnWO4 crystal scintillator has been determined at 5.4 standard deviations. These results open the possibility to realize a pioneering experiment to investigate the above-mentioned DM candidates by means of the directionality.