Patience is a virtue in the hunt for dark matter. Experiment after experiment has come up empty in the search — and the newest crop is no exception.
Observations hint at the presence of an unknown kind of matter sprinkled throughout the cosmos. Several experiments are focused on the search for one likely dark matter candidate: weakly interacting massive particles, or WIMPs (SN: 11/12/16, p. 14). But those particles have yet to be spotted.
Recent results, posted at arXiv.org, continue the trend. The PandaX-II experiment, based in China, found no hint of the particles, scientists reported August 23. The XENON1T experiment in Italy also came up WIMPless according to a May 18 paper. Scientists with the DEAP-3600 experiment in Sudbury, Canada, reported their first results on July 25. Signs of dark matter? Nada. And the SuperCDMS experiment in the Soudan mine in Minnesota likewise found no hints of WIMPs, scientists reported August 29.
Another experiment, PICO-60, also located in Sudbury, reported its contribution to the smorgasbord of negative results June 23 in Physical Review Letters.
Scientists haven’t given up hope. Researchers are building ever-larger detectors, retooling their experiments and continuing to expand the search beyond WIMPs.