‘Wimp’ particle offers clue to identity of dark matter

{"text":[[{"start":5.92,"text":"A flash of light in a huge tank 1.5km underground has provided the best clue yet to the nature of the mysterious “dark matter” that is at least five times more abundant than the ordinary matter in the visible universe."}],[{"start":20.439,"text":"The tell-tale flash occurred in a detector called Lux-Zeplin at the Sanford Underground Research Facility in South Dakota, one of several experiments around the world designed to identify particles of dark matter and solve the biggest puzzle in contemporary physics."}],[{"start":35.756,"text":"That flash was most likely caused by a particle of dark matter hitting an atomic nucleus in the detector’s 10 tonnes of liquid xenon, according to a scientific paper released on Tuesday at an astrophysics conference in Tokyo."}],[{"start":55.68,"text":"Scientists had long suggested that hypothetical “weakly interacting massive particles” made up dark matter but these Wimps had not previously been observed."}],[{"start":58.517,"text":"“Following a huge amount of scientific effort, this is incredibly exciting,” said Sam Eriksen of the University of Bristol, who led the international Lux-Zeplin study."}],[{"start":null,"text":"

"}],[{"start":68.656,"text":"“Scientists have been trying to better understand dark matter, which makes up the vast majority of matter in the universe, for nearly a century,” he said. “What we have observed in this analysis could be the first step in understanding dark matter as a particle.”"}],[{"start":83.166,"text":"The light signal in Lux-Zeplin’s underground tank was generated when a Wimp collided with a xenon atom, according to the study."}],[{"start":90.696,"text":"This Wimp would have a mass more than 200 times greater than a proton or neutron, the constituents of ordinary atoms. Such encounters with ordinary matter are extremely rare but physicists calculate that they must occasionally take place."}],[{"start":104.256,"text":"Almost all Wimps pass through ordinary matter as if it wasn’t there. “We don’t quite know the numbers but if you hold your finger up you get something like 100,000 Wimps through your fingertip every second and they’d be moving at about half a million miles an hour,” said Chamkaur Ghag, physics professor at University College London and a Lux-Zeplin researcher."}],[{"start":null,"text":""}],[{"start":125.28,"text":"The Lux-Zeplin result has not reached 5-sigma statistical significance, the conventional threshold for a discovery in physics, when there is less than one chance in a million that it is wrong. The latest analysis is 2.6-sigma, which means that there is a 0.5 per cent chance that the event could have another explanation such as a background effect that the researchers have not taken into account."}],[{"start":148.304,"text":"The study is based on 220 days of observations at Sanford Underground Research Facility. As more data accumulates, the findings will either grow in significance or fade away."}],[{"start":158.791,"text":"At the same time dark matter detectors in Italy, Canada and China — all buried deep underground to shield them from background radiation — will be on the lookout for similar evidence."}],[{"start":168.791,"text":"In addition to these underground labs, other laboratories are using different methods to search for incoming dark matter. At the Large Hadron Collider in Cern, Switzerland, for example, scientists are attempting to produce a new dark matter particle in high-energy collisions within an accelerator."}],[{"start":185.22,"text":"On the cosmic scale, observatories such as the Nancy Grace Roman Space Telescope launched on Sunday are assessing the effects of dark matter and its equally mysterious counterpart, dark energy, on the distribution of galaxies across the universe."}],[{"start":199.36,"text":"Even if the Lux-Zeplin discovery was confirmed, much would remain mysterious about the Wimp, including whether it was the main component of dark matter and whether it interacted with other undiscovered particles in the dark universe, said Ghag."}],[{"start":213.67,"text":"“Understanding dark matter and dark energy is beyond a shadow of doubt the biggest question in physics.”"}],[{"start":221.2,"text":""}]],"url":"https://audio.ftcn.net.cn/album/a_1788311685_4946.mp3"}