Dark Matter Experiment Detects Nothing, So Far
An experiment designed to detect evidence of so-far theoretical “dark matter” has ended its first phase with nothing detected, but scientists remain hopeful:
The former Homestake Gold Mine in Lead, S.D., has a hallowed place in the history of physics as a spot where nothing happens.
It was there, in the 1970s, that Raymond Davis Jr. attempted to catch neutrinos, spooky subatomic particles emitted by the sun, in a vat of cleaning fluid a mile underground and for a long time came up empty. For revolutionizing the study of those particles, he shared the Nobel Prize in Physics in 2002.
On Wednesday, an international team of physicists based in the same cavern of the former mine announced a new milestone of frustration, but also hope — this time in the search for dark matter, the mysterious, invisible ingredient that astronomers say makes up a quarter of the cosmos.
In the first three months of running the biggest, most sensitive dark matter detector yet — a vat of 368 kilograms of liquid xenon cooled to minus 150 degrees Fahrenheit — the researchers said they had not seen a trace of the clouds of particles that theorists say should be wafting through space, the galaxy, the Earth and, of course, ourselves, knocking out at least one controversial class of dark matter candidates.
But the experiment has just begun and will run for all of next year. The detector, already twice as sensitive as the next best one, will gain another factor of sensitivity in the coming run.
“Just because we don’t see anything in the first run doesn’t mean we won’t see anything in the second,” said Richard Gaitskell, a professor of physics at Brown University and a spokesman for an international collaboration that operates the experiment known as LUX, for the Large Underground Xenon dark matter experiment.
As has become de rigueur for such occasions, the scientists took pride and hope in how clearly they did not see anything. “In 25 years of searching, this is the cleanest signal I’ve ever seen,” Dr. Gaitskell said in an interview.
That meant, the scientists said, that their detector was working so well that they would easily see a dark matter particle if and when it decided to drop by.
The alternative, of course, is that the dark matter hypothesis is wrong, or that scientists are looking in the wrong place to determine the source of the gravitational forces holding galaxies together.