Dark-Matter Hunt Appears to Be Zeroing In on a Leading Contender

BY JENNIFER OUELLETTE,


Pity the poor physicist searching for dark matter, the exotic substance that accounts for roughly one-quarter of all the stuff in the cosmos, yet only interacts with the rest of the universe through gravity and the weak nuclear force. Hardly a week goes by, it seems, without a tantalizing new hint of a dark matter particle hovering at the threshold of statistical significance that eventually goes poof, dashing hopes yet again.

The search for dark matter involves a dizzying array of experiments, a veritable alphabet soup of acronyms, all using different techniques and technologies. This is how physicists look for something when they don’t know its precise properties. The problem is that although several experiments have detected possible hints of dark matter, the hints don’t agree with one another. Plot the color-coded results from various experiments onto a single graph, and it looks like abstract art.

Two years ago, Juan Collar of the University of Chicago was hopeful that dark matter was on the verge of being detected. But every subsequent new result seemed to point in a different direction. Small wonder that he opened a recent talk with a slide paraphrasing The Big Lebowski: “We are nihilists. We believe nothing.”

“We seem to be chasing our tails for the last two or three years,” Collar said in an interview.

The good news is that things might be looking up again. Physicists are seeing signs in the sky and deep underground, and they are looking for others at the Large Hadron Collider, which recently launched a hunt for dark matter. The whispers of dark matter are becoming louder, with a series of signals that seem to be converging toward a narrowed range. The bad news is that those hints still don’t agree exactly, and each hint on its own is “shaky,” according to the University of Michigan’s Kathryn Zurek. There remain many physicists who are skeptical that these will turn out to be dark matter signals. A few physicists are flirting with outright nihilism, including Collar, who said, “It’s hard not to be a nihilist the way things are going.”

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