The extent of the stop coannihilation strip

Many supersymmetric models such as the constrained minimal supersymmetric extension of the Standard Model (CMSSM) feature a strip in parameter space where the lightest neutralino χ is identified as the lightest supersymmetric particle, the lighter stop squark t~1 is the next-to-lightest supersymmetric particle (NLSP), and the relic χ cold dark matter density is brought into the range allowed by astrophysics and cosmology by coannihilation with the lighter stop squark t~1 NLSP. We calculate the stop coannihilation strip in the CMSSM, incorporating Sommerfeld enhancement effects, and we explore the relevant phenomenological constraints and phenomenological signatures. In particular, we show that the t~1 may weigh several TeV, and its lifetime may be in the nanosecond range, features that are more general than the specific CMSSM scenarios that we study in this paper