For 20 years, an experiment in Italy known as dama has detected an oscillating signal that could be coming from dark matter—the fog of invisible particles that ostensibly fill the cosmos, sculpting everything else with their gravity.
One of the oldest and biggest experiments hunting for dark-matter particles, dama is alone in claiming to see them. It purports to pick up on rare interactions between the hypothesized particles and ordinary atoms. But if these dalliances between the visible and invisible worlds really do produce dama’s data, several other experiments would probably also have detected dark matter by now. They have not.
In a new paper that’s causing some buzz, Daniel McKinsey, a physicist at UC Berkeley, contends that the signal could come from argon contamination. Certain isotopes of argon radioactively decay more or less depending on the season. Yet this explanation works only if the nitrogen dama uses in one step of their procedure contains argon, which is unknown.