Neutralino-proton cross sections in supergravity models

The neutralino-proton cross section is examined for supergravity models with R-parity invariance with universal and non-universal soft breaking. The region of parameter space that dark matter detectors are currently (or will be shortly) sensitive, i.e., (0.1-10) x 10(-6) pb, is examined. For universal soft breaking (mSUGRA), detectors with sensitivity sigma(<(chi)over bar>10-p) 1 x 10(-6) pb will be able to sample parts of the parameter space for tan beta greater than or similar to 25. Current relic density bounds restrict m(<(chi)over bar>10) less than or equal to 120 GeV for the maximum cross sections, which is below where astronomical uncertainties about the Milky Way are relevant. Nonuniversal soft breaking models can allow much larger cross sections and can sample the parameter space for tan beta greater than or similar to 4. In such models, m(0) can be quite large reducing the tension between proton decay bounds and dark matter analysis. We note the existence of two new domains where coannihilation effects can enter, i.e., for mSUGRA at large tan beta, and or nonuniversal models with small tan beta. (C) 2000 Elsevier Science B.V. All rights reserved.