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| gluino | |
|---|---|
| Name | Gluino |
| Type | Fermion |
| Spin | 1/2 |
| Color | Octet (adjoint) |
| Charge | 0 e |
| Mass | model-dependent |
| Status | Hypothetical |
gluino The gluino is the hypothetical fermionic superpartner of the gluon in supersymmetric extensions of the Standard Model. Proposed within supersymmetry frameworks such as the Minimal Supersymmetric Standard Model and variants developed by researchers including Howard Georgi and Sergio Ferrara, gluinos are color-octet Majorana fermions whose properties and interactions mirror those of gluons under quantum chromodynamics. Searches for gluinos have been central to experimental programs at facilities like CERN, Fermilab, and collaborations such as ATLAS and CMS.
In supersymmetric theories motivated by efforts from figures like Peter van Nieuwenhuizen and Julius Wess, each boson has a fermionic superpartner. The gluino arises as the partner of the gauge boson associated with the SU(3) gauge symmetry in quantum chromodynamics (QCD). Early theoretical work by groups including Noboru Sakai and Pierre Fayet formalized gluino interactions within gauge multiplets. Gluinos appear in model catalogs maintained by groups at DESY, SLAC, and national theory centers, and influence collider phenomenology, dark matter studies, and grand unified theories considered by researchers at institutions such as Princeton University and Institute for Advanced Study.
Gluinos are color-octet fermions transforming in the adjoint representation of SU(3) with no electroweak charge, similar to the gluon but with spin-1/2. In many constructions gluinos are Majorana particles, a possibility explored alongside Majorana neutrino hypotheses by theorists like Ettore Majorana and later analyzed by Rolf Hagedorn in model contexts. Their mass arises from supersymmetry breaking mechanisms studied in frameworks like gravity mediation, gauge mediation, and anomaly mediation, each developed by teams at institutions such as Harvard University and Institute for Theoretical Physics (Vienna). Renormalization group running of gluino masses ties them to squark spectra and gaugino unification conditions proposed in grand unified theory scenarios by researchers at Los Alamos National Laboratory and CERN.
Within the Minimal Supersymmetric Standard Model, gluinos mediate QCD-strength interactions between squarks and quarks analogous to gluon exchanges, affecting processes analyzed in studies by groups at Rutgers University and University of California, Berkeley. Their virtual effects enter precision observables measured by collaborations like LEP and Tevatron, and they contribute to loop corrections in Higgs-sector calculations pursued by teams at DESY and KEK. In gauge-coupling unification proposals championed by scholars at SLAC and University of Cambridge, gluino masses influence unification scales and proton-decay expectations tested by experiments such as Super-Kamiokande.
Gluinos would be produced copiously at hadron colliders via QCD processes: pair production through quark-antiquark annihilation or gluon-gluon fusion, processes studied in Monte Carlo programs developed by collaborations at CERN and Fermilab. Event topologies involving gluinos were modeled by groups working on PYTHIA and HERWIG event generators, with detector response simulated for experiments like ATLAS, CMS, and CDF. Proposed future facilities including the High-Luminosity Large Hadron Collider and proposed colliders discussed at ICFA workshops would extend sensitivity. Fixed-target and heavy-ion programs at RHIC provided complementary techniques for heavy colored state searches, while dedicated experiments at LHCb explored long-lived colored particle signatures.
Gluino decays depend on mass hierarchies and mediation mechanisms. If lighter than squarks, gluinos may undergo three-body decays through virtual squark exchange to produce jets plus neutralinos or charginos, decay patterns analyzed by theorists at University of Chicago and Columbia University. For scenarios with compressed spectra, gluino decays yield soft jets and missing transverse energy signatures pursued by CMS and ATLAS analyses. If gluinos are long-lived due to small phase space or suppressed couplings, they can form bound R-hadrons—color-singlet composites investigated by collaborations at CERN and modeled in lattice studies by groups at Brookhaven National Laboratory and Argonne National Laboratory. Such R-hadrons produce anomalous ionization, time-of-flight, and displaced-vertex signatures utilized in searches by LHCb and MoEDAL.
Searches at LEP provided indirect constraints via virtual effects, while direct exclusions have primarily come from Tevatron and LHC experiments. Results published by ATLAS and CMS set lower mass limits on promptly decaying gluinos in simplified models, with limits dependent on final state assumptions and analyses produced by collaborations at CERN. Long-lived gluino searches by ATLAS, CMS, and MoEDAL set complementary bounds using heavy-stable-charged-particle techniques and calorimeter timing, with reinterpretations by theory groups at IPPP (Durham) and CERN Theory refining constraints. Global fits incorporating results from Planck (spacecraft) and flavor experiments at Belle and BaBar examine indirect implications for gluino parameter space.
Gluino properties inform supersymmetry-breaking model building, dark matter frameworks promoted by researchers at University of Michigan and Stanford University, and grand unification scenarios developed at Los Alamos and CERN. The possibility of relatively light gluinos was explored in split supersymmetry proposals by theorists including Nima Arkani-Hamed and Savas Dimopoulos, whereas heavy gluinos appear in high-scale supersymmetry models considered at Perimeter Institute. Lattice QCD studies and nonperturbative analyses by groups at CERN and Brookhaven assess R-hadron spectroscopy, while precision collider phenomenology efforts at SLAC and DESY continue to refine signatures. Continued searches at international facilities and theoretical advances at universities such as Oxford and MIT will determine whether gluinos manifest or whether alternative mechanisms beyond supersymmetry explain observed phenomena.
Category:Hypothetical particles