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

Asymmetric Dark Matter (ADM) models relate the dark matter density to the baryon asymmetry, so that a natural mass scale for ADM is around a few GeV. In existing models of ADM, this mass scale is unexplained; here we generate this GeV scale for dark matter (DM) from the weak scale via gauge kinetic mixing with a new Abelian dark force. In addition, this dark sector provides an efficient mechanism for suppressing the symmetric abundance of DM through annihilations to the dark photon. We augment this sector with a higher dimensional operator responsible for communicating the baryon asymmetry to the dark sector. Our framework also provides DM candidate for gauge mediation models. It results in a direct detection cross section of interest for current experiments: σ p 10 −42 cm 2 for DM masses in the range 1 − 15 GeV.

Recently the PAMELA satellite-based experiment reported an excess of galactic positrons that could be a signal of annihilating dark matter. The PAMELA data may admit an interpretation as a signal from a wino-like LSP of mass about 200 GeV, normalized to the local relic density, and annihilating mainly into W-bosons. This possibility requires the current conventional estimate for the energy loss rate of positrons be too large by roughly a factor of five. Data from anti-protons and gamma rays also provide tension with this interpretation, but there are significant astrophysical uncertainties associated with their propagation. It is not unreasonable to take this well-motivated candidate seriously, at present, in part because it can be tested in several ways soon.

Color-octet scalars, if present at the TeV scale, will be produced in abundance at the LHC. We discuss in some detail the phenomenology of scalars in the (8, 2) 1/2 representation, recently identified by Manohar and Wise as an addition to the standard-model Higgs sector consistent with the principle of minimal flavor violation. Couplings of this multiplet to the Higgs lift the mass degeneracy among its states, possibly allowing for two-body decays of a heavier colored scalar to a lighter one and a gauge boson. We perform a renormalization group analysis of these couplings and find that limits from Tevatron searches leave little room for these decays. This fact, and the assumption of minimal flavor violation, lead us to study the case where the octets decay to the heaviest kinematically accessible fermion pairs. Focusing on pair-production events leading to tttt, bbbb, and bbtt final states, we find that discovery at the LHC should be possible up to masses exceeding 1 TeV. I. INTRODUCTIONIn the coming year, the Large Hadron Collider (LHC) will begin its exploration of the high-energy frontier, and may very well uncover evidence for physics beyond the Standard Model. Even if LHC data indicate dramatic departures from Standard Model predictions, determining the correct interpretation for these deviations will likely be a complex and challenging process. It is therefore worthwhile to consider a range of possibilities for what new physics might emerge, and to understand how these different possibilities would reveal themselves experimentally.Exotic scalars are one possibility. If they are to couple to standard-model fermions via renormalizable Yukawa couplings, the candidate representations for these scalars are actually rather limited. Under SU(3) C × SU(2) L , the allowed representations include Of these, some are well-known possibilities with well-developed phenomenology, e.g. leptoquarks [1]. Here, we will focus on scalars, S, in the (8,2) representation, which are not as well studied. Colored representations are of perhaps the most immediate interest, because they are the ones that will be copiously produced in the pp collisions at the LHC, assuming their masses lie near the TeV scale.What happens once S particles are produced? This depends in detail on their couplings to matter. If the S fields couple to fermions very weakly or not at all, they are stable for collider purposes, and the details of how they can be detected depend on how they hadronize. In the most pessimistic case, where S particles hadronize completely into neutral states, they are detectable through initial and final state radiation in a monojet search, as discussed for long-lived gluinos in Ref. [2]. Here we will focus on the case where the octets arXiv:0710.3133v2 [hep-ph]