Neutrinos, elusive fundamental particles, can act as a window into the center of a nuclear reactor, the interior of the Earth, or some of the most dynamic objects in the universe. Their tendency to change “flavors” may provide clues into the prominence of matter over antimatter in the universe or explain the existence of dark matter.

Physicists are particularly interested in proving the existence of “sterile” neutrinos. Their discovery would reveal a new form of matter that interacts only with gravity and could influence the evolution of the universe.

In a new study published in Physical Review Letters, a team of researchers from U.S. universities and national laboratories has set stringent limits on the existence and mass of sterile neutrinos. While they have yet to find the particles, they now know where not to look.