Ancient rocks may unearth dark matter

The visible universe—all the potatoes, gas giants, hot romance novels, black holes, questionable tattoos, and written-on sentences—makes up only 5 percent of the universe.

A team led by Virginia Tech is searching for the rest, not with telescopes or particle colliders, but by examining billions of years old rocks for traces of dark matter.

Patrick Huber, who studies physics, leads an interdisciplinary team from multiple universities in this unusual research, also taking an unusual step: from theoretical work to experimental work.

With support from a $3.5 million Growing Convergence Research award from the National Science Foundation and a separate $750,000 award from the National Nuclear Security Administration, Huber is building a new lab in Robeson Hall to test dark matter theories and see what else might come to light. building along the way.

Dark matter super dark

Scientists can only conclude the existence of dark matter because objects in the universe fall faster than they should around the centers of galaxies. The gravity of this unseen matter explains the extra attraction.

Unlike the bumps and crushes of ordinary matter, dark matter is thought to interact only very weakly with other matter; It cannot be detected except when it hits the nucleus of a visible matter atom. Retracting from the collision like an atomic billiard ball, the nucleus emits a spark of energy.

Over the past 50 years, physicists have performed all kinds of dark matter experiments in the hopes of witnessing one of these rare rebound events.

So far? Dark matter remained dark. Physicists have found no concrete evidence of dark matter. Now they’re coming back somewhere deep inside.

paleodetectives

If dark matter exists, there’s a chance it may have interacted with Earth at some point in its 4.6 billion year history. What about instead of waiting for dark matter to come to them?, Can scientists extract ancient evidence from minerals deep within the earth?

Although the idea of ​​using rocks as underground detectors was first proposed in the 1980s, technological advances have led researchers, including Huber, to rethink the idea.

“This is crazy. When I first heard this idea I thought: This is crazy. I want to do this,” said William E. Hassinger Jr. Senior Lecturer Huber.

Huber, a theoretical physicist, came up with a theory on how to solve this. But theory was not enough. If this plan were possible, he wanted to see what it would take to bring it to fruition.

“Other people in midlife crisis might take a mistress or buy a sports car. I have a laboratory,” Huber said.

Who stole the beans?

By developing and using sophisticated imaging techniques, Huber and his colleagues hope to reveal miniature traces of destruction left by long-ago dark matter interactions within crystal lattice structures.

When a high-energy particle hits a core inside a rock, the recoil of the explosive can dislodge the core, said Vsevolod Ivanov, a researcher at the National Security Institute at Virginia Tech who collaborated with Huber. The ejected nucleus and the empty space it leaves behind represent structural changes within the crystal.

“We will take a crystal that has been exposed to different particles for millions of years and extract distributions that correspond to things we know,” Ivanov said. “Everything that remains must be something new, and that could be dark matter.”

Most dark matter experiments are conducted underground to reduce interference from other high-energy particles called cosmic rays, but going underground presents a new set of problems. The planet pulsates with a radioactive background that can also shake the cores. Distinguished Professor of the University, Robert Bodnar, recently Inducted into the National Academy of SciencesHe will work with Huber’s team to identify, locate and characterize minerals that can be used as suitable detectors.

3D proof

To begin this massive imaging task, Huber is working with researchers at the University of Zurich’s Brain Research Institute, who have access to specialized microbiology imaging technology often used to image animal nervous systems.

The team has already begun creating 3D images of high-energy particle tracks in synthetic lithium fluoride. Huber said this artificial crystal will not be a good dark matter detector, but it will help detect any signals while keeping the crystal intact. In an unexpected development, applications of lithium fluoride imaging technology include “nuclear transparency devices” that could resemble backpack-sized monitoring devices for nuclear reactors.

Since the immediate value of tangential outputs from this “crazy” research goal has already been proven, Huber and his collaborators will dig deeper and look closer to see if an ancient rock can tell us how stars flew across the galaxy.