These X and Y bosons are called leptoquarks and can change quarks into leptons and vice-versa. This means that the proton could decay to mesons and leptons. For instance or One can calculate the proton lifetime in this model. The coupling g is the value at which the 3 running coupling constants meet and the mass of the X and Y particles is assumed to be around the energy at which they meet i.e . This predicts a proton lifetime between years and years.
Current measurements give lifetimes greater than to years depending on the decay mode.
Another prediction of GUTS are Magnetic Monopoles which carry magnetic but not electric charge. These have long been predicted but never seen. Detecting Proton Decay One gets low limits from the fact that humans are not radioactive or from the age of the earth etc. Better to watch protons for one year. A tracking capability for charged particles.