Target dark matter detection rates in models with a well-tempered neutralino

Abstract

In the post-LEP2 era, and in light of recent measurements of the cosmic abundance of colddark matter (CDM) in the universe from WMAP, many supersymmetric models tend topredict (i) an overabundance of CDM and (ii) pessimistically low rates for direct detectionof neutralino dark matter. However, in models with a ‘well-tempered neutralino’, where theneutralino composition is adjusted to give the measured abundance of CDM, theneutralino is typically of the mixed bino–wino or mixed bino–higgsino state. Alongwith the necessary enhancement to neutralino annihilation rates, these modelstend to give elevated direct detection scattering rates compared to predictionsfrom SUSY models with universal soft breaking terms. We present neutralinodirect detection cross sections from a variety of models containing a well-temperedneutralino, and find cross section asymptotes with detectable scattering rates. Theseasymptotic rates provide targets that various direct CDM detection experimentsshould aim for. In contrast, in models where the neutralino mass rather thanits composition is varied to give the WMAP relic density via either resonanceannihilation or co-annihilation, the neutralino remains essentially bino-like, and directdetection rates may be below the projected reaches of all proposed experiments.