Calculations of neutralino-stop coannihilation in the CMSSM

We present detailed calculations of the (χ) over tilde(t) over tilde (1) coannihilation channels that have the largest impact on the relic (χ) over tilde density in the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which scalar masses m(0), gaugino masses m(1/2) and the trilinear soft supersymmetry-breaking parameters A(0) are each assumed to be universal at some input grand unification scale. The most important (t) over tilde (1)(t) over tilde (1)* and (t) over tilde (1)(t) over tilde (1) annihilation channels are also calculated, as well as (t) over tilde (1)(l) over tilde coannihilation channels. We illustrate the importance of these new coannihilation calculations when A(0) is relatively large. While they do not increase the range of m(1/2) and hence m(%) allowed by cosmology, these coannihilation channels do open up new 'tails' of parameter space extending to larger values of m(0). (C) 2002 Elsevier Science B.V. All rights reserved.