The Large Hadron Collider may have discovered why we don't live in a universe of antimatter

The Large Hadron Collider is constantly on the hunt for "new physics" — discoveries that confound and expand our current understanding of the universe... and it may have found one in the decay patterns of a subatomic particle and its antimatter counterpart.

Photo via NASA/Chandra Observatory.

Specifically, particles called D-mesons appear to decay in a slightly different way than their antiparticles, and this seemingly small finding could explain why the early universe became dominated by matter instead of antimatter. According to project physicist Matthew Charles, the results have a statistical certainty of 3.5 sigma - meaning there's a 99.95% chance that these results will hold up, but still short of the 5 sigma level needed to declare this a formal discovery. However, the team still has a huge amount of data still to work through, so there's an excellent chance that we'll know one way or the other about this result in the near future.

So what exactly is going on here? The result comes from the LHCb Collaboration, one of six ongoing experiments at the Large Hadron Collider. This particular experiment is focused on the decay of particles known as bottom quarks, one of the most massive quarks. D-mesons are particles containing charm quarks that are created in this decay process, and which can in turn decay into other particles called kaons and pions.

According to our currently understanding of physics, the decay process for a D-meson and an anti-D-meson should be identical to within 0.1%, and that's been backed up by previous experiments at less powerful particle accelerators like the one at Fermilab. But the LHCb Collaboration is able to probe the decay rate with far more precision than previous generation accelerators, and the physicists have discovered the decay rate actually varies by 0.8%.

Dr. Charles explains the potential importance of this finding:

"Certainly this kind of effect, a new source of CP violation, could be a manifestation of the physics which drives the matter - antimatter asymmetry. This result is a hint of something interesting and if it bears out, it will mean that, at a minimum, our current theoretical understanding needs improving. It's exactly the sort of thing for which the LHC was originally built."

It may not seem like much, but even a 0.8% imbalance in these decay rates could have made all the difference in the evolution of the early universe. By creating just a tiny inequality in one type of subatomic particle in the aftermath of the Big Bang, matter could have completely overwhelmed antimatter, annihilating the antiparticles while still leaving more than enough particles left over to build the known universe. There's still a ways to go before this can be considered a formal discovery — or indeed, for its full impact on the early universe to be understood — but this is still a seriously exciting find for the Large Hadron Collider.

Original findings via BBC News. Photo of LHCb Collaboration via official website.