From dark matter to squirrels

The advantage of the snowball chamber over many other experimental setups is that if a passing dark matter particle gives even the tiniest nudge to the nucleus of an atom in supercooled water, it can trigger the water to spontaneously freeze. If all other possible causes of nucleation are eliminated, this would indicate that an interaction with a dark matter particle occurred.Unlike other methods that attempt to detect dark matter, which are suited for hunting particles hundreds to thousands of times heavier than the mass of a proton, the researchers point out the snowball chamber might allow them to expand their search to lower mass alternatives — including dark matter particles less than about a dozen times the mass of a proton."All of my work is motivated by the search for dark matter, a form of matter we're sure is out there because we can observe its indirect gravitational effects," said Szydagis. "It makes up a significant fraction of the universe, but we have yet to uncover direct, conclusive and unambiguous evidence of it within the lab."Although the researchers point out the sensitivity of the snowball chamber is currently below the threshold needed to detect low-mass dark matter particles, they have identified where improvements can be made. According to the study, they will continue to work on increasing both the purity of the water and the cleanliness of the container, as well as supercooling the water to even lower temperature than the -4 F (-20 C) they achieved. Additionally, since particle physics is often a numbers game, they would like to increase the size of the snowball chamber so it can hold tens — or even hundreds — of kilograms of supercooled water.But that's much farther down the road. "Since this is basic research that has never been done before, there was no guarantee it would work," Szydagis said. "It was a 'let's try it and see' approach — the scientific method in its most basic form."Though the newly developed snowball chamber may one day aid in the hunt for dark matter, the paper points out that it could be used for studying other worthwhile topics. For example, according to the paper, "Planets like those in the Trappist-1 system close to a red dwarf star [produce] more radiation than our Sun." If these planets have supercooled water in their atmospheres, they "may experience different cloud formation rates and climate than currently modelable."But astrophysics is not the only discipline that may benefit from research carried out with the snowball chamber. Atmospheric scientists could also use it to study how cosmic rays may trigger the nucleation of supercooled water in Earth's atmosphere. Or, according to the paper, "in biochemistry, our new result may affect the study of animals which capitalize on supercooling of their blood," like the arctic ground squirrel "All in all, this is a promising start to a completely new technology," the APS presentation concluded. preprint of the research is available for review on arXiv.org.