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.

The naturalness of a Higgs boson with a mass near 125 GeV is explored in a variety of weak-scale supersymmetric models. A Higgs mass of this size strongly points towards a non-minimal implementation of supersymmetry. The Minimal Supersymmetric Standard Model now requires large A-terms to avoid multi-TeV stops. The fine-tuning is at least 1% for low messenger scales, and an order of magnitude worse for high messenger scales. Naturalness is significantly improved in theories with a singlet superfield S coupled to the Higgs superfields via λSH u H d . If λ is perturbative up to unified scales, a fine-tuning of about 10% is possible with a low mediation scale. Larger values of λ, implying new strong interactions below unified scales, allow for a highly natural 125 GeV Higgs boson over a wide range of parameters. Even for λ as large as 2, where a heavier Higgs might be expected, a light Higgs boson naturally results from singlet-doublet scalar mixing. Although the Higgs is light, naturalness allows for stops as heavy as 1.5 TeV and a gluino as heavy as 3 TeV. Non-decoupling effects among the Higgs doublets can significantly suppress the coupling of the light Higgs to b quarks in theories with a large λ, enhancing the γγ and W W signal rates at the LHC by an order one factor relative to the Standard Model Higgs.

This document proposes a collection of simplified models relevant to the design of new-physics searches at the Large Hadron Collider (LHC) and the characterization of their results. Both ATLAS and CMS have already presented some results in terms of simplified models, and we encourage them to continue and expand this effort, which supplements both signature-based results and benchmark model interpretations. A simplified model is defined by an effective Lagrangian describing the interactions of a small number of new particles. Simplified models can equally well be described by a small number of masses and cross-sections. These parameters are directly related to collider physics observables, making simplified models a particularly effective framework for evaluating searches and a useful starting point for characterizing positive signals of new physics. This document serves as an official summary of the results from the 'Topologies for Early LHC Searches' workshop, held at SLAC in September