Higgs with mass can lead to all of the operators suppressed by . See doublet–triplet splitting problem. Dimension-5 proton decay operators In supersymmetric extensions (such as the MSSM), we can also have dimension-5 operators involving two fermions and two sfermions caused by the exchange of a tripletino of mass M. The sfermions will then exchange a gaugino or Higgsino or gravitino leaving two fermions. The overall Feynman diagram has a loop (and other complications due to strong interaction physics). This decay rate is suppressed by where MSUSY is the mass scale of the superpartners. Dimension-4 proton decay operators In the absence of matter parity, supersymmetric extensions of the Standard Model can give rise to the last operator suppressed by the inverse square of sdown quark mass. This is due to the dimension-4 operators c and ccc. The proton decay rate is only suppressed by which is far too fast unless the couplings are very small. See also Age of the universe B − L Virtual black hole Weak hypercharge X and Y bosons References Further reading External links Proton decay at Super-Kamiokande Pictorial history of the IMB experiment Proton Nuclear physics Physics beyond the Standard Model Grand Unified Theory Supersymmetric quantum field theory Hypothetical processes Ultimate fate of the universe 1967 in science ja:陽子#陽子の崩壊