ORCA (Oscillations Research with Cosmics in the Abyss) is the low-energy branch of KM3NeT, the underwater Cherenkov neutrino detector in the Mediterranean.
Its primary goal is to resolve the long-standing unsolved question of the neutrino mass ordering by measuring matter oscillation effects in atmospheric neutrinos.
In addition, the detection of neutrinos from the self-annihilation reactions of particles in the GeV-TeV mass range will represent the first evidence of a Dark Matter signal.
To be deployed at the French KM3NeT site, ORCA's multi-PMT optical modules will exploit the excellent optical properties of deep seawater to reconstruct cascade and track events with a few GeV of energy.