Abstract
Using the latest LHC data, we analyse and compare the lower limits on the masses of gluinos and the lightest stop in two natural supersymmetric motivated scenarios: one with a neutralino being the lightest supersymmetric particle (LSP) and the other one with gravitino as the LSP and neutralino as the next-to-lightest supersymmetric particle. In the second case our analysis applies to neutralinos promptly decaying to very light gravitinos, which are of cosmological interest, and are generic for low, of order mathcal{O} (100) TeV, messenger scale in gauge mediation models. We find that the lower bounds on the gluino and the lightest stop masses are stronger for the gravitino LSP scenarios due to the extra handle from the decay products of neutralinos. Generally, in contrast to the neutralino LSP case the limits now extend to a region of compressed spectrum. In bino scenarios the highest excluded stop mass increases from 1000 GeV to almost 1400 GeV. Additionally, in the higgsino-like NLSP scenario the higgsinos below 650 GeV are universally excluded and the stop mass limit is {m}_{tilde{t}} > 1150 GeV, whereas there is no limit on stops in the higgsino LSP model for {m}_{tilde{h}} = 650 GeV. Nevertheless, we find that the low messenger scale still ameliorates the fine tuning in the electroweak potential.
Highlights
On the corresponding LHC signatures1 [17, 18]
In the second case our analysis applies to neutralinos promptly decaying to very light gravitinos, which are of cosmological interest, and are generic for low, of order O(100) TeV, messenger scale in gauge mediation models
In this paper we have compared the lower bounds on the gluino and stop masses in two supersymmetric scenarios, one with neutralino as the lightest supersymmetric particle (LSP) and the other one with neutralino decaying into gravitino
Summary
We focus on models that have been motivated by the concept of natural SUSY, we consider spectra where among light particles we have gauginos/higgsinos, serving as the (next-to-lightest) supersymmetric particle, stops and gluinos. A stop-gluino model where both particles are within or close to kinematic reach of the LHC and no definite mass hierarchy is assumed. In all the models the strongly interacting particles are accompanied by electroweakinos: either the higgsino doublets, wino triplet or bino singlet — which are assumed to be lighter than the stops and gluinos. The mass hierarchy is as follows: mg, mt1 > mχ (> m3/2) These models are parametrised by the masses of participating particles: mg, mt, mχ. Since we assume that only one type of electroweakinos is present at a time, the mixing between gaugino-higgsino states is neglected, which implies that the additional charginos and neutralinos are almost mass degenerate with the lightest neutralino
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