Scintillation from slow protons: A probe of monopole detection capabilities

We describe an experiment which has detected light emission from a plastic scintillator due to neutron-induced recoil protons with initial energies as small as 410 eV. The velocity of such protons is smaller than that expected of grand-unified-theory magnetic monopoles. Searches for these exotic particles will therefore not be limited by kinematic or adiabatic constraints at velocities in excess of 9×${10}^{\mathrm{-}4}$c.