Gluino

About: Gluino is a research topic. Over the lifetime, 1921 publications have been published within this topic receiving 60868 citations.

The Neutralino relic density in minimal $N=1$ supergravity

Abstract: We compute the cosmic relic (dark-matter) density of the lightest supersymmetric particle (LSP) in the framework of minimal [ital N]=1 supergravity models with radiative breaking of the electroweak gauge symmetry. To this end, we recalculate the cross sections for all possible annihilation processes for a general, mixed neutralino state with arbitrary mass. Our analysis includes effects of all Yukawa couplings of third-generation fermions, and allows for a fairly general set of soft supersymmetry- (SUSY-) breaking parameters at the Planck scale. We find that a cosmologically interesting relic density emerges naturally over wide regions of parameter space. However, the requirement that relic neutralinos do not overclose the Universe does not lead to upper bounds on SUSY-breaking parameters that are strictly valid for all combinations of parameters and of interest for existing or planned collider experiments; in particular, gluino and squark masses in excess of 5 TeV cannot strictly be excluded. On the other hand, in the generic'' case of a gauginolike neutralino whose annihilation cross sections are not accidentally'' enhanced by a nearby Higgs boson or [ital Z] pole, all sparticles should lie within the reach of the proposed [ital pp] and [ital e][sup +][ital e[minus]] supercolliders. We also find thatmore » requiring the LSP to provide all dark matter predicted by inflationary models imposes a strict lower bound of 40 GeV on the common scalar mass [ital m] at the Planck scale, while the lightest sleptons would have to be heavier than 100 GeV. Fortunately, a large relic neutralino density does not exclude the possibility that charginos, neutralinos, gluinos, and squarks are all within the reach of the CERN [ital e][sup +][ital e[minus]] collider LEP 200 and the Fermilab Tevatron.« less

Natural SUSY Endures

Abstract: The first 1 fb−1 of LHC searches have set impressive limits on new colored particles decaying to missing energy. We address the implication of these searches for naturalness in supersymmetry (SUSY). General bottom-up considerations of natural electroweak symmetry breaking show that higgsinos, stops, and the gluino should not be too far above the weak scale. The rest of the spectrum, including the squarks of the first two generations, can be heavier and beyond the current LHC reach. We have used collider simulations to determine the limits that all of the 1 fb−1 searches pose on higgsinos, stops, and the gluino. We find that stops and the left-handed sbottom are starting to be constrained and must be heavier than about 200–300 GeV when decaying to higgsinos. The gluino must be heavier than about 600–800 GeV when it decays to stops and sbottoms. While these findings point toward scenarios with a lighter third generation split from the other squarks, we do find that moderately-tuned regions remain, where the gluino is just above 1 TeV and all the squarks are degenerate and light. Among all the searches, jets plus missing energy and same-sign dileptons often provide the most powerful probes of natural SUSY. Overall, our results indicate that natural SUSY has survived the first 1 fb−1 of data. The LHC is now on the brink of exploring the most interesting region of SUSY parameter space.