Using the Universe to calculate the mass of a dark matter candidate
This year, the Large Hadron Collider has produced more than 10 times the data that it generated in the previous year's run. While most of that hasn't been analyzed yet, none of the data looked at so far contains an obvious sign of one of the Universe's big mysteries: a dark matter particle. With each year's failure to turn up a WIMP (weakly interacting massive particle), it gives us a little more motivation to consider alternatives.
One of the more compelling alternatives is a particle called an axion. Axions were first proposed to solve a different problem in physics, one involving the forces that pulls quarks and gluons together to form things like protons and neutrons. But if axions exist and have mass, they would seem to have the properties needed to produce the effects we ascribe to dark matter.
One nice thing about axions is that, since they have to perform another role, their properties are a bit constrained. Now, a team of researchers have used that fact to calculate the mass we should expect an axion to have. The input parameters to that calculation? Nothing more than the Universe itself.