Antimatter hunt closes in on the Big Bang’s biggest head-scratcher

Chris Davies - Apr 16, 2020, 12:16pm CDT
Antimatter hunt closes in on the Big Bang’s biggest head-scratcher

One of the core secrets of the universe could be another step closer to a solution, with scientists making a huge breakthrough in understanding matter and antimatter and the interplay between the two. Little-comprehended and shrouded with questions, antimatter theory has nonetheless become a key part of many explanations about modern physics. However uncertainty about its proportions has continued to frustrate researchers.

Each particle of matter, so modern physics suggests, would have a corresponding antiparticle of antimatter. That would have the same mass, but an opposite electric charge, among other things. Collisions between the two would lead to mutual annihilation.

What that doesn’t explain is why there’s not more antimatter out there. The universe – at least the observable universe – is mostly made up of matter. Antimatter, however, is far rarer, rather than the 50-percent that you’d expect it to comprise had the Big Bang which created the universe generated both types of energy in equal measure.

“When particle physicists make new particles in accelerators, they always find that they produce particle-antiparticle pairs: for every negative electron, a positively charged positron,” Professor Lee Thompson, a physicist at the University of Sheffield’s Department of Physics and Astronomy, and one of an international team of scientists involved in the new antimatter research explains. “So why isn’t the universe 50 per cent antimatter? This is a long-standing problem in cosmology – what happened to the antimatter?”

The so-called T2K experiment involved more than 350 scientists around the world, using the SuperKamiokande detector to observe neutrinos and antineutrinos that had been generated at the Japanese Proton Accelerator Research Complex (J-PARC). Those sites are more than 180 miles apart, and as the elementary particles travel through the Earth they oscillate between different physical properties. These are known as “flavors.”

Comparing the flavor at the origin, and at the point of detection, the T2K team realized there was a mismatch in the way the neutrinos and antineutrinos oscillate. That asymmetry in their physical properties – charge-conjugation and parity reversal (CP) violation – could explain why matter is so abundant but antimatter is so rare.

The findings have been published in Nature this week. Though no exact conclusions about the matter/antimatter question have been reached, the study does reach an important three standard deviation confidence interval, the degree of statistical significance which indicates the CP violation is indeed being observed.

Future studies hope to use this as the basis for new experiments, which could come closer to understanding why antimatter is missing. In turn, that could address one of the biggest questions remaining around the Big Bang and the formation of our universe.


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