… in the fact that their instruments are now much more sensitive, so if it were there, they would not be missing it:
From the New York Times:
As has become de rigueur for such occasions, the scientists took pride and hope in how clearly they did not see anything. “In 25 years of searching, this is the cleanest signal I’ve ever seen,” Dr. Gaitskell said in an interview.
…
Dark matter has teased and tantalized physicists since the 1970s, when it was demonstrated that some invisible material must be providing the gravitational glue to hold galaxies together. Determining what it is would provide insight into particles and forces not described by the Standard Model that now rules physics, not to mention a slew of Nobel Prizes.
Physicists’ best guess is that this dark matter consists of clouds of exotic subatomic particles left over from the Big Bang and known generically as WIMPs, for weakly interacting massive particles, which would weigh several hundred times as much as a proton but could nevertheless pass through the Earth like smoke through a screen door. They are a generic feature of a much-hyped idea known as supersymmetry.
Dark matter is currently thought to comprise a quarter of the universe.
What would cosmology look like if it is never detected?