This week a bunch of scientists crawled out of a deep hole in South Dakota, then they flew to Sheffield University to announce that the dark matter they were looking for was being elusive, after spending 20 months underground trying to find it.
The announcement was made at a Dark Matter conference at the University of Sheffield on Thursday, a five-day event where scientists from all over the world researching dark matter came together to share their findings. The LUX researchers’ findings show that dark matter was more elusive than they initially thought, despite the expense to build a first-of-its-kind sensor to look for dark matter, neutrinos and weakly interacting massive particles (WIMPS) deep inside a South Dakota mine.
For years, scientists have been searching for the existence of dark matter as the reason galaxies rotate and light bends as it travels through the universe.
The theory behind dark matter is that it is undetectable in our electromagnetic spectrum, but the effect it has on other matter outside of it proves that it exists. Many confuse dark matter with dark energy, but they are in fact two separate things.
A press release by the Sanford Underground Research Facility, which set up the underground lab, described why they could not detect the elusive particles. The researchers explained that sensitivity of the detector was initially increased by four times more than the goal they set for themselves, and worked hard to make sure they thoroughly held the sensitivity without interference from outside elements.
Part of the detection process is to isolate cooled liquid xenon in a container by surrounding it with water to prevent interference from outside particles, which they surround with instruments to detect the interaction of the xenon particles with outside particles, hoping to catch a flash when the elusive dark matter collides.
The press release provides details of the careful collaboration of those instruments and quotes physics professor Dan McKinsey on the details.
“As the charge and light signal response of the LUX experiment varied slightly over the dark matter search period, our calibrations allowed us to consistently reject radioactive backgrounds, maintain a well-defined dark matter signature for which to search and compensate for a small static charge buildup on the Teflon inner detector walls.”
The year-and-a-half experiment allowed them to thoroughly test out various models they initially constructed to know how to detect dark matter, and now that they’ve discovered how difficult the elusive matter is to find, they can approach other experiments in the future around newer models.
Rick Gaitskell also explained the next step in their in their search.
“We viewed this as a David and Goliath race between ourselves and the much larger Large Hadron Collider (LHC) at CERN in Geneva. LUX was racing over the last three years to get first evidence for a dark matter signal. We will now have to wait and see if the new run this year at the LHC will show evidence of dark matter particles, or if the discovery occurs in the next generation of larger direct detectors.”
The end of the experiment however doesn’t mean the end of LUX, as the next step is to increase the size of the xenon container, thereby ramping up the sensitivity by 70 times. The new project, named LUX Zeplin (LZ), is set to go online in 2020.
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The press release also offers details on the support the project gained since it employed miners, who were once with the mining company operating the mine before Sanford University set up their operation in it. The South Dakota Science and Technology Authority (SDSTA) reopened the mine in 2007 to prepare for the dark matter experiment, using $110 million in total funds from the South Dakota legislature and philanthropist T. Denny Sanford.
Twenty universities and national laboratories from Portugal, the United Kingdom and the United States were also involved with the research, which got additional support from the Department of Energy and the National Science Foundation. Researchers will be going over the collected data to narrow down their search for the elusive dark matter for future experiments.