arXiv:hep-ph/9806361v2 21 Sep 1998 University of California - Davis UCD-98-8 FSU-HEP-980612 hep-ph/9806361 June, 1998 Revised: September, 1998 A HEAVY GLUINO AS THE LIGHTEST SUPERSYMMETRIC PARTICLE Howard Baer 1,2 , Kingman Cheung 1 and John F. Gunion 1 1 Davis Institute for High Energy Physics University of California, Davis, CA 95616 2 Department of Physics, Florida State University Tallahassee, FL 32306 Abstract We consider the possibility that the lightest supersymmetric particle is a heavy gluino. After discussing models in which this is the case, we demon- strate 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 anal- yses. 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. 1 Introduction In the conventional minimal supergravity (mSUGRA) and minimal gauge-mediated (mGMSB) supersymmetry models, the gaugino masses M i at low energy are pro- 1