Neutralino
In supersymmetry, the neutralino is a hypothetical particle. In the Minimal Supersymmetric Standard Model (MSSM), a popular model of realization of supersymmetry at a low energy, there are four neutralinos that are fermions and are electrically neutral, the lightest of which is stable in an R-parity conserved scenario of MSSM. They are typically labeled N͂01 (the lightest), N͂02, N͂03 and N͂04 (the heaviest) although sometimes χ ~ 1 0 , … , χ ~ 4 0 {\displaystyle {\tilde {\chi }}_{1}^{0},\ldots ,{\tilde {\chi }}_{4}^{0}} is also used when χ ~ i ± {\displaystyle {\tilde {\chi }}_{i}^{\pm }} is used to refer to charginos.