Аннотация:

Among all the possible signals of new physics at the LHC search for dark matter particles in different models and in «model-independent» portal approaches occupies an important place. In this context, checking the predictions of supersymmetric theories, primarily the MSSM and its various extensions, has always looked very attractive, because of its well-motivated nature and optimistic estimates of the possibilities of experimental study at the LHC. Unfortunately, the two previous cycles of operation of this accelerator, RUN1 and RUN2, showed no signs of new physics or indications of the expected signals. The standard analysis with a large missing transverse momentum in events and with prompt decays in supersymmetric cascades (which occurs very close to the production point of the primary particles and in very short times), has, in fact, almost reached its limits. However, this approach leaves completely uncovered a fairly large class of models and signals that can still be studied at the LHC. We are talking about long-lived particles (LLP), which participate in decay chains and greatly change the usual picture and approach to physical analysis. In the talk I discuss a proposal to dark matter search in the stealth supersymmetry model. The long lifetime of intermediate states is ensured due to the close mass degeneracy, and the possibility for the lightest stable neutral superpartner to have a small and even very small mass gives a non-standard signature with small energy losses, which, however, still can be observed at the LHC.