Scientists are still hard at work seeking answers regarding dark matter. This mysterious substance, known as dark energy, constitutes about 68% of the total mass-energy content of the universe. The search for dark matter particles, known as weakly-interacting massive particles (WIMPs), remains one of the most challenging puzzles in contemporary astrophysics. The CRESST experiment — located deep beneath the Gran Sasso Mountain in central Italy — is leading this hunt.
Dark matter has a very large possible mass range of more than 50 orders of magnitude. Initially, it was theorized that the mass of a dark matter particle could be as low as 10^-21 electron-volts (eV). In comparison, the range of individual dark matter particle masses is between 10^24 and 10^30 eV. This mass is on par with that of a single bacterium or a very small insect. This huge range of possible masses makes the search for these elusive particles even more difficult.
Weakly Interacting Massive Particles (WIMPs) are a leading candidate for dark matter. Their mass typically ranges from a few billion to a trillion electron volts. This mass range places them in the company of other heavy particles, like the W and Z bosons and top quark. Other contenders for the dark matter role include Q-balls, WIMPzillas, and sterile neutrinos. Each of these in turn helps widen the intricate and strange field of possible explanations of why dark matter exists.
The CRESST experiment has been operating for several years but has yet to confirm the detection of a dark matter particle. It has a huge crystal of calcium tungstate, more commonly known as Scheelite. This specialized crystal is designed to sense collisions between wimps and ordinary atoms.
“Structure of the CRESST experiment, whose aim is to find dark matter particles. Credit: A. Eckert”
CRESST is far from the only initiative dedicated to this pursuit. Researchers from countries all over the globe have participated in dozens of direct detection experiments. Most of these experiments employ scintillators paired with enormous pools of liquefied noble gases, like xenon. These experiments are looking to find definitive evidence that dark matter exists. This enigmatic material has only been hinted at through indirect observations until now.
Even with these challenges, researchers are looking ahead and finding hope in all the untapped discoveries awaiting us right around the corner. One researcher stated, “WIMPs aren’t the greatest idea in all of physics, and the whole dark matter hypothesis is all built on circumstantial evidence. Of all the options we’ve got, it’s the least bad one we have.”
The quest for dark matter represents, more than almost any other area of inquiry, the intricacies, allure and unpredictability of contemporary physics. As scientists refine their methods and technologies, they strive to unlock new insights into one of the universe’s most profound mysteries.