SUSY model and dark matter determination in the compressed-spectrum region at the ILC

Understand

It is an appealing possibility that the observed dark matter density in the universe can be fully explained by SUSY.

• The current experimental knowledge indicates that this possibility strongly favors a co-annihilation scenario.
• In such scenarios, the mass difference between the next-to-lightest SUSY particle (the NLSP) and the lightest one (the LSP) is quite small, which assures that the annihilation cross-section is sufficient not to predict a too large abundance of dark matter.
• However, the small mass difference also means that observing SUSY becomes hard at hadron colliders, where the observation hinges on the tell-tale signature of missing transverse energy: if the mass difference NLSP-to-LSP is small, only little energy is carried away by the invisible LSP.