Editing Proton decay (section)

=== Dimension-4 proton decay operators ===

[[Image:R-parity violating decay.svg|frame|right]]

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 {{math|{{SubatomicParticle|Quark}}{{SubatomicParticle|Lepton}}{{SubatomicParticle|Down squark}}{{sup|c}}}} and {{math|{{SubatomicParticle|Up quark}}{{sup|c}}{{SubatomicParticle|Down quark}}{{sup|c}}{{SubatomicParticle|Down squark}}{{sup|c}}}}.

The proton decay rate is only suppressed by <math display="inline"> 1/M_\text{SUSY}^2 </math> which is far too fast unless the couplings are very small.