Experimental Test of the Conservation of Nucleons

An improved measurement has been made of the lower limit for the lifetime of nucleons against spontaneous decay by processes which do not conserve the number of nucleons. The decay modes considered release charged particles with energies generally in excess of 100 Mev. Possible decay events were sought with a 200-liter liquid scintillation detector. Backgrounds were due entirely to cosmic rays which were reduced by going 585 m underground and then surrounding the scintillation detector by a water Čerenkov anticoincidence counter of over-all dimensions 2.4 m in diameter and 2.0 m high. The scintillation detector was set to detect pulses as low in energy as 8 Mev and hence was sensitive to a wider variety of decay events than previous experiments. Lifetime limits obtained range from 1×${10}^{26}$ to 7×${10}^{27}$ years depending on the decay mode assumed.