The Brown University researchers analyzed data collected over three years by NASA's Fermi gamma-ray space telescope and measured the number of photons emitted from the dwarf galaxies. From the number of photons, they were able to determine the rate of quark production... which in turn allowed them to establish constraints on the mass of dark matter particles.
Based on the known rate of the expansion of the universe and the rate at which particles in the dwarf galaxies canceled each other out, Koushiappas and Geringer-Sameth reported that dark matter must have a mass greater than 40 giga-electron volts (GeV).
"What we find is if a particle's mass is less than 40 GeV, then it cannot be the dark matter particle," said Koushiappas.
Previous reports of dark matter WIMPs by researchers at the Gran Sasso facility in Italy showed particles in the 7 to 12 GeV range, much lower than the Brown researchers' limit. This will help narrow down the range of what defines dark matter particles.
"This is the first time that we can exclude generic WIMP particles that could account for the abundance of dark matter in the universe," Koushiappas said.