The End of the CMSSM Coannihilation Strip is Nigh

Abstract

A recent global fit to the CMSSM incorporating current constraints on supersymmetry, including missing transverse energy searches at the LHC, BR(B_s to mu+ mu-) and the direct XENON100 search for dark matter, favours points towards the end of the stau-neutralino (stau_1- chi) coannihilation strip with relatively large m_1/2 and 10 < tan beta < 40 and points in the H/A rapid-annihilation funnel with tan beta ~ 50. The coannihilation points typically have m_stau_1-m_chi < 5 GeV, and a significant fraction, including the most-favoured point, has m_stau_1-m_chi < m_tau. In such a case, the stau_1 lifetime would be so long that the stau_1 would be detectable as a long-lived massive charged particle that may decay inside or outside the apparatus. We show that CMSSM scenarios close to the tip of the coannihilation strip for tan beta < 40 are already excluded by LHC searches for massive charged particles, and discuss the prospects for their detection in the CMS and ATLAS detectors via time-of-flight measurements, anomalous heavy ionization or decays into one or more soft charged particles.