Prospects for Sparticle Discovery in Variants of the MSSM

We discuss the prospects for detecting supersymmetric particles in variants of the minimal supersymmetric extension of the Standard Model (MSSM), in light of laboratory and cosmological constraints. We first assume that the lightest supersymmetric particle (LSP) is the lightest neutralino chi, and present scatter plots of the masses of the two lightest visible supersymmetric particles when the input scalar and gaugino masses are constrained to be universal (CMSSM), when the input Higgs scalar masses are non-universal (NUHM), and when the squark and slepton masses are also non-universal and the MSSM is regarded as a low-energy effective field theory valid up to the GUT scale (LEEST) or just up to 10 TeV (LEEST10). We then present similar plots in various scenarios when the LSP is the gravitino. We compare the prospects for detecting supersymmetry at linear colliders (LCs) of various energies, at the LHC, and as astrophysical dark matter. We find that, whilst a LC with a centre-of-mass energy E_{CM} <= 1000 GeV has some chance of discovering the lightest and next-to-lightest visible supersymmetric particles, E_{CM} >= 3000 GeV would be required to `guarantee' finding supersymmetry in the neutralino LSP scenarios studied, and an even higher E_{CM} might be required in certain gravitino dark matter scenarios. Direct dark matter experiments could explore part of the low-mass neutralino LSP region, but would not reveal all the models accessible to a low-energy LC.