Simplified models for dark matter searches at the LHC

Abstract

International audienceThis document outlines a set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these simplified models have when applied to dark matter searches at the LHC, and to provide a number of useful expressions for reference. The list of models includes both s-channel and t-channel scenarios. For s-channel, spin-0 and spin-1 mediation is discussed, and also realizations where the Higgs particle provides a portal between the dark and visible sectors. The guiding principles underpinning the proposed simplified models are spelled out, and some suggestions for implementation are presented

Robustness of dark matter constraints and interplay with collider searches for New Physics

“…The main background for monojet searches stems from Z or W -boson and a jet, with the Z-boson decaying to neutrinos and the W -boson decaying to leptons which are missed by the detector. Considering models in which a single mediator relates the dark matter particles to the SM particles reveals that the LHC can have a competitive or even superior reach compared to the dark matter detection experiments [176][177][178][179]. However, the simple description of dark matter production at the LHC based on a single mediator is not realistic with regard to concrete models such as the pMSSM, in which co-annihilations are favoured by the relic density constraints.…”

“…This is generally true for simplified dark matter models [179], because the relic density is directly related to the annihilation cross sections. However, in a complete model such as the MSSM, the value of the relic density is often led by the co-annihilations, especially when both the upper and lower bounds of the Planck dark matter density measurements are applied.…”

Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS

“…Ref. [3]). Such models are characterized by the most important state mediating the DM particle interactions with the SM and hence explicitly include the particles at higher masses, as well as the DM particle itself.…”

“…5.1, two approaches are commonly used to model generic processes yielding a nal state with a particle X recoiling against a system of noninteracting particles, either with an e ective eld theory (EFT) framework [8], where particles that mediate the interactions between DM and SM particles are too heavy to be produced directly in the experiment and are described by contact operators, or using simpli ed models that are characterized by a minimal number of renormalizable interactions and hence explicitly include the particles at higher masses [3]. The two approaches are complementary and both are included in this analysis.…”

“…One option is to use nonrenormalizable operators in an e ective eld theory (EFT) framework [8], where particles that mediate the interactions between DM and SM particles are too heavy to be produced directly in the experiment and are described by contact operators. Alternatively, simpli ed models that are characterized by a minimal number of renormalizable interactions and hence explicitly include the particles at higher masses can be used [3]. The EFT approach is more modelindependent, but is not valid when a typical momentum transfer of the process approaches the energy scale of the contact operators that describe the interaction.…”