Gauginos

Gauginos are the fermionic superpartners of the gauge bosons in supersymmetric theories. In the Minimal Supersymmetric Standard Model (MSSM) there are three gauge groups—SU(3) for color, SU(2) for weak isospin, and U(1) for hypercharge—whose gauge bosons have corresponding gauginos: the gluino (partner of the gluon), winos (partners of the SU(2) gauge bosons, producing charged winos), and bino (partner of the U(1) hypercharge gauge boson). In practice, the electroweak gauginos mix with the higgsinos, the fermionic partners of the Higgs fields, to form the physical mass eigenstates known as neutralinos and charginos. Neutralinos are neutral Majorana fermions arising from mixtures of bino, wino, and higgsinos; charginos are charged fermions arising from mixtures of charged winos and charged higgsinos. The gluino is a color-octet Majorana fermion and does not mix with the electroweak gauginos in the simplest constructions.

Gaugino masses originate from supersymmetry breaking and are described by soft terms M1, M2, and M3 for bino, wino, and gluino, respectively. Depending on the model, these masses can obey high-scale relations, such as universality in certain scenarios, which influence the expected spectrum of gauginos and their mixing with higgsinos.

Gauginos interact through gauge couplings and can be produced at colliders via strong or electroweak processes. Their decays typically proceed through cascades that end with the lightest supersymmetric particle (LSP), often a neutralino, which is stable if R-parity is conserved and a candidate for dark matter. No experimental confirmation of gauginos has been observed to date; current searches at the Large Hadron Collider set limits that depend on the assumed mass spectrum and decay patterns.