For more than a decade, scientists have known that the subatomic particles called charm mesons can travel as a mixture of their particle and antiparticle states. Now, a new discovery made by Oxford physicists analyzing data from the Large Hadron Collider (LHC, part of CERN) is showing for the first time that they can also oscillate between these two states.
Achieving the discovery was no small feat. "What makes this discovery of oscillation in the charm meson particle so impressive is that, unlike the beauty mesons, the oscillation is very slow and therefore extremely difficult to measure within the time that it takes the meson to decay," Professor Guy Wilkinson of the University of Oxford said in a statement.
"This result shows the oscillations are so slow that the vast majority of particles will decay before they have a chance to oscillate. However, we are able to confirm this as a discovery because LHCb has collected so much data."
To come to their conclusion the physicists used data collected during the second run of the Large Hadron Collider and found a difference in mass between the two particles of 0.00000000000000000000000000000000000001 grams – or in scientific notation 1x10-38 g.
Ultimately, although this latest work does offer new insights, a number of questions still remain about the nature and function of antimatter. Case in point, when the Big Bang occurred some 13.8 billion years ago, both matter and antimatter should have been created in equal amounts.
And since the two annihilate each other when they come into contact, we should live in a massive, black void. An empty expanse without planets, or stars, or life. However, as we all know, we live in a matter-dominated cosmos, which means that there was more matter than antimatter.
To find out what caused this difference, and uncover more information about the birth and evolution of our universe, particle physicists have been trying to test the properties of matter and antimatter to compare them. For matter, this is actually pretty simple. Matter exists, and we can easily interact with it. But remember that antimatter is annihilated (along with matter) the moment the two come into contact.
This obviously makes studying antimatter exceedingly challenging. Specifically, keeping it intact long enough for a detailed investigation is difficult. Over the years, scientists have gotten better at isolating increasing quantities of antimatter in a vacuum for longer and longer periods, which has enabled a host of new research breakthroughs. But despite all of the recent breakthroughs, like the observations mentioned here, we still don't know why we have a universe of matter instead of antimatter.
In fact, to explain the matter-antimatter problem, we know that something in the Standard Model of physics must be wrong. The Standard Model is the framework that explains all known subatomic particles and fundamental forces except gravity. So if something is wrong with the Standard Model, something is fundamentally wrong with our understanding of physics and, by extension, the universe itself.
However, scientists hope that breakthroughs like the one made here might, eventually, finally reveal the nature of antimatter.