Gluino

The gluino is the fermionic superpartner of the gluon in supersymmetric theories. It is a Majorana fermion transforming in the adjoint (octet) representation of SU(3) color. Its mass and other properties arise from supersymmetry breaking, and in many models it lies in the range from hundreds of GeV to multi-TeV.

Gluinos interact primarily through the strong force, with couplings proportional to the strong coupling constant. They belong to the gauge sector alongside the gluon and other gauginos and are produced at colliders mainly in gluon-gluon and quark-antiquark collisions, typically in pairs.

Decays depend on the superpartner spectrum. When squarks are lighter than the gluino, the two-body decay gluino -> quark + squark dominates, with the squark then decaying to a quark and a neutralino or chargino. If squarks are heavier, gluinos decay via off-shell squarks to multi-body final states, typically quark-antiquark plus a neutralino or chargino. In models with R-parity conservation, the lightest supersymmetric particle (often the neutralino) is stable, leading to missing energy signatures. In some scenarios, long-lived gluinos hadronize into R-hadrons and can traverse detectors.

Experimental status: No discovery of gluinos has been reported. LHC searches for jets plus missing energy and dedicated R-hadron analyses have set lower limits on the gluino mass that depend on decay modes and spectrum; typical bounds lie around 1–2 TeV for many simplified model assumptions. The bounds are weaker for compressed spectra or for long-lived gluinos.

The gluino is a central component of many supersymmetric theories, influencing collider phenomenology, precision observables, and dark matter considerations. While it is not itself a dark matter candidate in standard scenarios, its properties affect the viability of neutralino dark matter and the overall SUSY parameter space.