Dark matter already sounds like something out of a science fiction movie, but now imagine a lab under a mountain where scientists are trying to detect any trace of it with an enormous vat of liquid xenon.
The XENON1T experiment is that vat, aka the most sensitive dark matter detector ever, surrounded by a team of scientists trying to bring dark matter to light, deep under a mountain in Gran Sasso, Italy. Those often-controversial theories on how to prove the existence of this mysteriously abundant stuff that cannot be touched or seen might be onto something. 85% of the matter in the entire universe is believed to be invisible and intangible. You’d think that much matter floating around in the chasm of space would have to eventually be picked up by some other method if it eludes the human eye. Nothing yet from the XENON1T experiment, but at least they got the thing to work.
“I think the most exciting thing is the fact that the detector works as we expect,” said professor Laura Baudis of the Physik Institut of the University of Zurich.
Dark matter supposedly swarms with infinitesimal particles, which were previously thought to have only weak interactions with nuclei of “normal” matter atoms. Enter the liquid xenon. Forward-thinking physicists theorize that dark matter particles could produce light particles and knock an electron out when they slam into xenon nuclei. This process would spark two subsequent photon signals. How much time elapses between the photon signal from the initial collision and the next from the electron knockout would depend on where the epic crash happened. The signal would then be amped by photomultiplier tubes that would make it show up like a blip on a digital screen. It’s sort of like atomic pinball.
“These first results demonstrate that XENON1T has the lowest low-energy background level ever achieved by a dark matter experiment,” said Baudis and her team in a recent publication. “The sensitivity of XENON1T is the best to date.”
XENON1T has only seen a month’s worth of data, so the research team is still optimistic. Scientists will ultimately determine whether dark matter can be identified at the mass detectable by the experiment’s sensitivity. At the very least, it could take several years to come to any sort of conclusion about the existence or non-existence of something so elusive. The sheer size of this experiment improves the chance of detection—but seeing nothing in the end won’t necessarily black out dark matter theories. Since we already don’t know where to look, we might just need to look elsewhere.