We propose a new class of models called Little Z models in order to reduce the fine-tuning due to the current experimental limits on the Z mass in E 6 inspired supersymmetric models, where the Higgs doublets are charged under the extra U (1) gauge group. The proposed Little Z models allow a lower mass Z due to the spontaneously broken extra U (1) gauge group having a reduced gauge coupling. We show that reducing the value of the extra gauge coupling relaxes the experimental limits, leading to the possibility of low mass Z resonances, for example down to 200 GeV, which may yet appear in LHC searches. Although the source of tree level fine-tuning due to the Z mass is reduced in Little Z models, it typically does so at the expense of increasing the vacuum expectation value of the U (1) -breaking standard model singlet field, reducing the fine-tuning to similar levels to that in the Minimal Supersymmetric Standard Model.
We point out that the extra neutralinos and charginos, generically appearing in a large class of E6 inspired models, lead to distinctive signatures from gluino cascade decays involving longer decay chains, more visible transverse energy, softer jets and leptons and less missing transverse energy than in the Minimal Supersymmetric Standard Model (MSSM). On the one hand, this makes the gluino harder to discover for certain types of conventional analysis. On the other hand, the E6 inspired models have enhanced 3-and 4-lepton signatures, as compared to the MSSM, making the gluino more visible in these channels. After extensive scans over the parameter space, we focus on representative benchmark points for the two models, and perform a detailed Monte Carlo analysis of the 3-lepton channel, showing that E6 inspired models are clearly distinguishable from the MSSM in gluino cascade decays.
We point out that the extra neutralinos and charginos generically appearing in a large class of E6 inspired models lead to distinctive signatures from gluino cascade decays in comparison to those from the Minimal Supersymmetric Standard Model (MSSM). These signatures involve longer decay chains, more visible transverse energy, higher multiplicities of jets and leptons, and less missing transverse energy than in the MSSM. These features make the gluino harder to discover for certain types of conventional analyses, for example in the 6 jet channel we show that a 1 TeV MSSM gluino may resemble an 800 GeV E6 gluino. However, the enriched lepton multiplicity provides enhanced 3-and 4-lepton signatures, which are much more suppressed in the case of the MSSM. As an example we analyse various scenarios in the E6SSM, demonstrating the utility of a CalcHEP model that we have now made publicly available on HEPMDB (High Energy Physics Models DataBase). After extensive scans over the parameter space, we focus on representative benchmark points. We perform detailed Monte Carlo analyses, concentrating on the 3-lepton channel at the 7, 8, and 14 TeV Large Hadron Collider (LHC), and demonstrate that E6 inspired models are clearly distinguishable from the MSSM in gluino cascade decays. We emphasise to the LHC experimental groups that the distinctive features present in gluino cascade decays, such as those discussed here, not only represents a unique footprint of a particular model but also may provide the key to an earlier discovery of supersymmetry.
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