Why do we exist? The most profound question there is and one that may seem completely outside the scope of particle physics. But our new experiment at CERN’s Large Hadron Collider has taken us a step closer to figuring it out.
Why the universe we see today is made entirely out of matter is one of the greatest mysteries of modern physics. Had there ever been an equal amount of antimatter, everything in the universe would have been annihilated. Our research has unveiled a new source of this asymmetry between matter and antimatter.
Antimatter was first postulated by Arthur Schuster in 1896, given a theoretical footing by Paul Dirac in 1928, and discovered in the form of anti-electrons, dubbed positrons, by Carl Anderson in 1932. The positrons occur in natural radioactive processes, such as in the decay of Potassium-40.
This means your average banana (which contains Potassium) emits a positron every 75 minutes. These then annihilate with matter electrons to produce light. Medical applications like PET scanners produce antimatter in the same process.
Antimatter particles should in principle be perfect mirror images of their normal companions. But experiments show this isn’t always the case. Take for instance particles known as mesons, which are made of one quark and one anti-quark.
Neutral mesons have a fascinating feature: they can spontaneously turn into their anti-meson and vice versa. In this process, the quark turns into an anti-quark or the anti-quark turns into a quark.
But experiments have shown that this can happen more in one direction than the opposite one – creating more matter than antimatter over time.
While we still cannot completely solve the mystery of the universe’s matter-antimatter asymmetry, our latest discovery has opened the door to an era of precision measurements that have the potential to uncover yet unknown phenomena. There’s every reason to be optimistic that physics will one day be able to explain why we are here at all.