Physicists have narrowed the mass range for hypothetical dark matter axions
Bit by bit, physicists are winnowing down the potential masses for hypothetical particles called axions. If they exist, the subatomic particles could make up dark matter, a mysterious source of mass that pervades the universe. Axions are expected to be extremely lightweight — billionths or trillionths the mass of an electron. But there were no sightings of the elusive particles in a mass range between 2.81 millionths and 3.31 millionths of an electron volt (between about 5.5 trillionths and 6.5 trillionths of an electron’s mass), physicists with the ADMX experiment report in a paper in press in Physical Review Letters. Scientists expect axions to have masses between a millionth and a thousandth of an electron volt. Previously, ADMX searched a small range of masses, and scientists are now expanding that range (SN: 4/9/18). The new result is “one step on a long road to exploring the whole plausible range,” says physicist Gray Rybka of the University of Washington in Seattle, co-spokesperson of ADMX. Another team...