Scrutinizing LSP Dark Matter at the LHC

Abstract

We show that LHC experiments might well be able to determine all the parameters required for a prediction of the present density of thermal LSP relics from the Big Bang era. If the LSP is an almost pure bino we usually only need to determine its mass and the mass of the SU(2) singlet sleptons. This information can be obtained by reconstructing the cascade $\tilde{q}_L \to \tildeχ_2^0 q \to \tilde{\ell}_R \ell q \to \tildeχ_1^0 \ell^+ \ell^- q$. The only requirement is that $m_{\tilde{\ell}_R} < m_{\tildeχ_2^0}$, which is true for most of the cosmologically interesting parameter space. If the LSP has a significant higgsino component, its predicted thermal relic density is smaller than for an equal--mass bino. We show that in this case squark decays also produce significant numbers of $\tildeχ_4^0$ and $\tildeχ_2^\pm$. Reconstructing the corresponding decay cascades then allows to determine the higgsino component of the LSP.