R-parity is a concept in particle physics. In the supersymmetric extension of the Standard Model, baryon number and lepton number are no longer conserved by all of the renormalizable couplings in the theory. Since baryon number and lepton number conservation have been tested very precisely, these couplings need to be very small in order not to be in conflict with experimental data. R-parity is a symmetry acting on the Minimal Supersymmetric Standard Model (MSSM) fields that forbids these couplings and can be defined as:
- PR = (-1)2s+3B+L.
Or, equivalently, as:
- PR = (-1)3(B-L)+2s.
With spin s, baryon number B, and lepton number L. All Standard Model particles have R-parity of 1 while supersymmetric particles have R-parity -1.
Read more about R-parity: Dark Matter Candidate, R-parity Violating Couplings of The MSSM, Proton Decay, Possible Origins of R-parity