A possible return on race

Third generation superparticles search is one of the main goals of the present LHC activities.

Previous LHC data has been especially effective in ruling out the existence of coloured supersymmetric particles (primarily the gluino and the first two generations of s-quarks) with masses below \sim 1\ TeV. However, such constraints are relaxed, in some cases by as much as a factor of two, in more generic frameworks of the MSSM.

The main production mechanisms of massive coloured s-particles at hadron colliders are squark-squark, squark-gluino and gluino-gluino production.

The typical SUSY search signature at hadron colliders contains high p_T jets which are produced in the decay chains of heavy squarks and gluinos, and significant missing momentum originating from the two LSPs produced at the end of the decay chain. The main s-bottom decay modes include the decay to either the lightest or the second lightest neutralino (\tilde{\chi}_2^0) plus ab quark (\tilde{b}_1 \rightarrow b\tilde{\chi}_1^0,b\tilde{\chi}_2^0), or to charginos via\tilde{b}_1\rightarrow t\tilde{\chi}_1^\pm.
In scenarios where the s-bottom is produced in pairs and decays chiefly via\tilde{b}_1\rightarrow b\tilde{\chi}_1^0, signal events have ab\overline{b}\tilde{\chi}_1^0 \tilde{\chi}_1^0 final state.

No excess has been observed in data above the Standard Model predictions and the current exclusion limits reach s-top and s-bottom masses at the level of 600\div 700\ GeV in models with one step decays such as\tilde{b}_1\rightarrow b\tilde{\chi}_1^0 or \tilde{t}_1\rightarrow t\tilde{\chi}_1^0.

Although the search for SUSY at the LHC has just begun, the results of the ATLAS and CMS experiments are already probing direct production of SUSY particles at the 1\ TeV mass scale. So far, no evidence of new particle production has been observed in the data and therefore, limits on allowed parameter space in various models have been set.

While typically s-quark and gluino masses around 1\ TeV and below are excluded in constrained models, weaker bounds on SUSY particle masses are obtained in less constrained scenarios demonstrating that SUSY below the 1\ TeV scale is certainly not ruled out in general. The impact of the LHC is to a large extent yet to come, and limits from LEP and the Tevatron are still competitive, for non-coloured s-particles.

Like the experimental landscape of SUSY searches, the field of global interpretations of allowed SUSY parameters is still rapidly changing. Yet, it seems reasonable to expect that the emphasis on interpretations in constrained SUSY models is now shifting towards more flexible models, which in turn motivates an even stronger experimental emphasis on searches for direct production of third generation s-quarks, of electroweak gauginos, or involving compressed m_{mother}-m_{\tilde{\chi}_1^0} mass spectra.

An increased emphasis on R-parity violating models and on models with long-lived particles can also be expected.

 

References and further readings
PDG, Review of Particle Physics (Phys. Rev. D, 86), 2012, 010001
J. Poveda on behalf of the ATLAS and CMS Collaborations, Third generation superpartners: Results from ATLAS and CMS, [arXiv:1402.6253v1], 2014
A. Cakir, Searches for Supersymmetry with the CMS Experiment, [arXiv:1111.4820v1], 2011
The CMS Collaboration, Searches for new physics in the multijet
and missing transverse momentum final state in proton–proton collision at \sqrt{s}= 8\ TeV, [arXiv:1402.4770v1], 2014
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