Neutrino event reconstruction with the liquid-argon target of SAND in the DUNE Near Detector.

SAND (System for on-Axis Neutrino Detection) will be the on-axis beam monitor in the Near Detector of the DUNE experiment, aiming at controlling the flux and systematics uncertainties for the oscillation analysis. It consists of a solenoidal magnet, an electromagnetic calorimeter, an inner tracker system and a 1-ton liquid-argon target named GRAIN (GRanular Argon for Interaction of Neutrinos). GRAIN will allow to collect samples of $\nu$-Ar interactions, exploiting the reconstruction power of the downstream systems and its own calorimetric light readout to precisely infer the incoming neutrino energy. In addition, innovative optical imaging systems based on coded apertures or UV lenses are envisioned to boost GRAIN capabilities by using scintillation light to spatially reconstruct the tracks and provide topological information of the events. In this contribution, the design of GRAIN and its optical readout are described, as well as the expected reconstruction performance of neutrino events in liquid argon within SAND.