Signal modulation in cold-dark-matter detection

If weakly interacting massive.particles (WIMPS) are the dark matter in the galactic halo, they may be detected in low background ionization detectors now operating or with low temperature devices under development. In detecting WIMPS of low msss or WIMPS with spin-dependent nuclear interactions (e.g., photinos), a principal technical difficulty appears to be achieving very low thresh- olds (5 O(keV)) in large (- kg) detectors with low background noise. We present an analytic treatment of WIMP detection and show that the seasonal modula- tion of the signal can be used to detect WIMPS even at low signal-twbackground levels and thus without the necessity of going to very low energy thresholds. As a result, the prospects for detecting a variety of cold dark matter candidates may be closer at hand than previously thought. We discuss in detail the detector characteristics required for a number of WIMP candidates, and carefully work out expected event rates for several present and proposed detectors.