About a kilometre underground in an abandoned gold mine, one of the most important quests in physics has come up empty-handed in the search for the elusive substance known as dark matter, scientists say.
The most advanced Earth-based search for the mysterious material that has mass but cannot be seen turned up "absolutely no signal" of dark matter, said Richard Gaitskell of Brown University, a scientist working on the Large Underground Xenon experiment.
A detector attached to the International Space Station has so far also failed to find any dark matter.
Physicists released their initial findings on Wednesday after the experiment's first few months of operation at the Sanford Underground Research Facility, which was built in the former Homestake gold mine in South Dakota's Black Hills.
With 1400 meters of earth helping screen out background radiation, scientists tried to trap dark matter, which they hoped would be revealed in the form of weakly interacting massive particles, nicknamed WIMPS.
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The search, using the most sensitive equipment in the world, tried looking for the light fingerprint of a WIMP bouncing off an atomic nucleus of xenon cooled to minus minus 101 Celsius.
But nothing was found, said co-investigator Daniel McKinsey, a physicist at Yale University.
The team plans to keep looking for another year, but McKinsey and Gaitskell were not optimistic about finding dark matter with the current setup.
They are already planning to build a more sensitive experiment on the site, using a bigger tank of xenon.
