Supersymmetric dark matter and the energy of a linear electron-positron collider

We suggest that supersymmetric dark matter be used to set the energy scale of a linear e(+)e(-) collider. Assuming that the lightest supersymmetric particle (LSP) is a stable neutralino chi, as in many incarnations of the MSSM with conserved R parity, previous calculations that include coannihilation effects have delineated the region of the (m(1/2),m(0)) plane where the LSP cosmological relic density lies in the preferred range 0.1 less than or similar to Omega(chi)h(2) less than or similar to 0.3, We evaluate here the total cross section for e(+)e(-) --> visible pairs of supersymmetric particles, for different values of m(1/2) and m(0), and investigate how much of the dark matter region can be explored by e(+)e(-) colliders with different centre-of-mass energies E-CM. We find that a collider with E-CM = 500 GeV or 1 TeV can only explore part of the cosmological region, and that a collider with E-CM = 1.5 TeV with sufficient luminosity can explore all of the supersymmetric dark matter region. (C) 2000 Published by Elsevier Science B.V. All rights reserved.