Simplified Dark Matter Models

Searches for new physics at the LHC are often interpreted in terms of simplified models. Simplified models provide a generic framework for analysing experimental signatures using a small number of parameters, such as masses and couplings of new fields, without reference to specific UV-complete models. Such an approach is particularly well-suited for interpreting the search for Dark Matter (DM) in a more model-independent way, and can be used to connect results from the LHC with dark matter searches in direct detection and from the observation of cosmic rays.

Several models are on the market. The ones below have all have a vector mediator. The first has a majorana fermion as the DM candidate, and the mediator only couples to first generation quarks (the model considered in [112]). The second is the same but the mediator couples to all generations of quarks. The third and fourth have a Dirac fermion as DM, and are considered in several CMS analysis and in the ATLAS summary [47], with various options for coupling to quarks and leptons.

Light Scalars decaying to gauge bosons

R-Parity-Violating Supersymmetry

Supersymmetric extensions of the SM typically conserve a quantum number known as R-Parity, written as \(R_p = (−1)^{3B+L+2S}\). This has the effect of suppressing proton decay, excluding the single production of supersymmetric particles, and ensuring the stability of the lightest SUSY particle (LSP). However, the most general SUSY lagrangian allows R-Parity violating (RPV) terms; subsets of these terms can be included in a model without inducing unacceptably high rates of proton decay. RPV superymmetric models retain many of the theoretical motivations of supersymmetry (and may in some cases even retain a viable Dark Matter candidate). However, R-Parity violation in general can change the collider phenomenology significantly. For example in many cases the LSP decay removes the typical missing momentum signatures upon which many collider searches rely. For this reason the phenomenology of RPV models has been studied at past colliders (see for example [63][106][184]) and is currently a topic of interest at the LHC [161], perhaps especially as more conventional SUSY searches continue to draw blanks.