The first observation of baryonic matter and antimatter behaving differently was presented on Monday by an international team of physicists from CERN. The result announced at the Rencontres de Moriond conference marks a milestone in the history of particle physics. This fundamental discovery expands our understanding of the differences between matter and antimatter and opens up new ways for scientists to understand why at the origin of the universe it was matter that won.
Cosmological models assume that the so-called Big Bang created equal amounts of matter and antimatter. However, one of the great unsolved mysteries of cosmology is why, instead of all particles and their antiparticles disappearing, leaving only radiation, a small amount of matter remained. The explanation of the mystery might be facilitated by the CERN physicists’ discovery.
The theory presumes that matter in our world should behave just like antimatter in the mirror world, but as long as 60 years ago physicists observed a violation of this state, known as CP-symmetry, in particles called mesons. The same behaviour was then predicted also for the other main group of particles – baryons – which include protons and neutrons constituting atomic nuclei. It was, however, not until the Large Hadron Collider (LHC) at CERN provided enough data that these expectations were confirmed.
"The new discovery by scientists from the LHCb experiment opens the door for further theoretical and experimental studies of the nature of CP-symmetry violation, which may show us the way to look beyond the Standard Model for new physics," explains physicist Tomáš Jakoubek from the Institute of Physics of the Czech Academy of Sciences. He has been working in this field at CERN for 15 years and recently joined the LHCb experiment.
All known particles, their behaviour and interactions are described by the Standard Model of Elementary Particle Physics. "Despite all the success of this model and its predictive power (for example, the Higgs boson prediction), it is not a perfect theory – for example, it does not describe gravity, it cannot explain dark matter and dark energy, and although it predicts CP-symmetry violation, it does so on a much smaller scale than is needed to explain the observed asymmetry in the universe. Because of these and other shortcomings, physicists believe that the Standard Model will eventually be extended or replaced by a better theory, just as Newtonian mechanics was eventually replaced by Einstein's general theory of relativity," Jakoubek said.