Heavy gluino as the lightest supersymmetric particle

Abstract

We consider the possibility that the lightest supersymmetric particle is a heavy gluino. After discussing models in which this is the case, we demonstrate that the g-LSP could evade cosmological and other constraints by virtue of having a very small relic density. We then consider how neutral and charged hadrons containing a gluino will behave in a detector, demonstrating that there is generally substantial apparent missing momentum associated with a produced g-LSP. We next investigate limits on the g-LSP deriving from LEP, LEP2 and RunI Tevatron experimental searches for excess events in the jets plus missing momentum channel and for stable heavily-ionizing charged particles. The range of m g that can be excluded depends upon the path length of the g in the detector, the amount of energy it deposits in each hadronic collision, and the probability for the g to fragment to a pseudo-stable charged hadron after a given hadronic collision. We explore how the range of excluded m g depends upon these ingredients, concluding that for non-extreme cases the range 3 GeV < ∼ m g < ∼ 130 − 150 GeV can be excluded at 95% CL based on currently available OPAL and CDF analyses. We find that RunII at the Tevatron can extend the excluded region (or discover the g) up to m g ∼ 160 − 180 GeV. For completeness, we also analyze the case where the g is the NLSP (as possible in gauge-mediated supersymmetry breaking) decaying via g → g + gravitino. We find that the Tevatron RunI data excludes m g ≤ 240 GeV. Finally, we discuss application of the procedures developed for the heavy g-LSP to searches for other stable strongly interacting particles, such as a stable heavy quark.

Stable colored particles R-SUSY relics or not?

“…Both direct searches for dark matter and searches for anomalously heavy seawater [52] preclude dark matter from having SU(3) C charge. This places strong limits on the mass of any new stable colored particle; gluinos, for example, can evade cosmological bounds only if their masses are less than about a TeV [39], and seawater tests may lower the allowed mass to ∼ 100 GeV.…”

Non-baryonic dark matter

“…There are other possible production mechanisms and cosmological scenarios for massive axinos. 6 Even if the primordial population of axinos is inflated away (which would happen if the reheating temperature T reh ≪ f a ), they can be regenerated from thermal background processes at high enough T reh .…”

“…The axial couplings (6) are determined by the experimental values of the spin constants ∆u (p) = ∆d (n) = 0.78, ∆d (p) = ∆u (n) = −0.5 and ∆s (p) = ∆s (n) = −0.16. The effective couplings d q depend on the WIMP properties and for the neutralino they can be found, e.g., in the Appendix of Ref.…”

“…On the other hand, they could in principle carry color charges. (For example, a stable gluino above 130 − 150 GeV [6], or in an experimentally allowed window 25 − 35 GeV [7], could still be the lightest SUSY particle (LSP) although its relic abundance would be very small [6].) In a halo they would exist as neutral states by forming composites with gluon or quarks.…”

Collider phenomenology of light strange-beauty squarks

“…Some theoretical studies on massive stable charged particles exist for gluino LSP models [13], colored Higgs bosons and Higgsinos [14], and scalar leptons [15].…”