SNO+ begins search for "invisible" mode of nucleon decay

The SNO+ detector, recently filled with ultra pure water, is searching for neutrons that spontaneously decay into three neutrinos.  The neutrinos coming from this decay would leave the detector undisturbed (they're invisible to us).  However, the disappearance of the neutron from an oxygen nucleus will often emit several gamma rays, which would readily be seen inside SNO+.  This special type of nucleon decay is one of the dominant modes predicted by particle physics models with Universal Extra Dimensions.