CERN's LHCb experiment hints at why universe has more matter than antimatter

Why do we exist? This is arguably 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.To understand why let’s go back in time some 13.8 billion years to the Big Bang. This event produced equal amounts of the matter you are made of and something called antimatter. It is believed that every particle has an antimatter companion that is virtually identical to itself but with the opposite charge. When a particle and its antiparticle meet, they annihilate each other – disappearing in a burst of light.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.[caption id="attachment_6307761" align="alignnone" width="1280"] The Milky Way as seen from Yellowstone National Park. Image courtesy: Neal Herbert/Flickr[/caption]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.The fundamental building blocks of matter that make up atoms are elementary particles called quarks and leptons. There are six kinds of quarks: up, down, strange, charm, bottom and top. Similarly, there are six leptons: the electron, muon, tau and the three neutrinos. There are also antimatter copies of these twelve particles that differ only in their charge.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.[caption id="attachment_5904501" align="alignnone" width="1280"] CERN's concept for the Future Circular Collider dwarfs the existing LHC experiment. Image: CERN[/caption]

Third time’s a charm

Next steps

The discovery will be followed by an increased number of theoretical works, which help to interpret the result. But more importantly, it will outline further tests to deepen the understanding following our finding – with a number of such tests already ongoing.Over the coming decade, the upgraded LHCb experiment will boost the sensitivity for these kinds of measurements. This will be complemented by the Japan-based Belle II experiment, which is just starting to operate. These are exciting prospects for research into matter-antimatter asymmetry.Antimatter is also at the heart of a number of other experiments. Whole anti-atoms are being produced at CERN’s Antiproton Decelerator, which feeds a number of experiments conducting high precision measurements. The AMS-2 experiment aboard the International Space Station is on the lookout for antimatter of cosmic origin. And a number of current and future experiments will tackle the question of whether there is antimatter-matter asymmetry among neutrinos.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.Marco Gersabeck, Lecturer in Physics, University of ManchesterThis article is republished from The Conversation under a Creative Commons license. Read the original article.