Hello folks! Welcome to the second episode of ‘Antimatter Unraveled’! Today, we are going to understand the discovery of CP violation, an asymmetry in processes producing matter and antimatter, in processes involving strange quarks. But, if you haven’t read the first episode yet, you would like to check it out to understand what antimatter is and how it was discovered!

In this vast and intricate universe, one of the greatest mysteries that continues to baffle physicists is the question of why our universe is dominated by matter rather than antimatter. The observable universe seems to be overwhelmingly composed of matter, however, according to the Standard Model of particle physics and the principles of quantum field theory, the Big Bang should have produced equal amounts of both.  To understand this imbalance, scientists have explored the subtle intricacies of particle physics which led to one of the most significant discoveries; THE CP VIOLATION.

Let’s first try to grasp the concept of CP symmetry in brief. Here, ‘C’ stands for charge conjugation; which is a transformation that swaps a particle with its antiparticle, and ‘P’ stands for parity; a transformation that inverts the spatial coordinates, while creating a mirror image of a physical system. These two transformations, known as CP symmetry, should result in leaving the laws of physics unchanged.

In 1964, James Cronin and Val Fitch led an experiment and studied the behavior of neutral kaons, particles containing a strange quark and a down antiquark. Kaons are known for their ability to oscillate between their particle and antiparticle states. However, this experiment revealed that the decay of kaons did not always respect CP symmetry.

Kaons, as we already discussed, belong to a group of particles called mesons, which are composed of a quark and an antiquark. The strange quark which is present in kaons plays a crucial role in the CP violation. The inclusion of Strange Quarks in the study of CP violation has been remarked as a significant asymmetry in the laws of physics.

There are two ways in which the CP violation gets manifested in the system of kaon; indirect and direct. Indirect CP violation occurs when the mixing between the kaon and its antiparticle states does not preserve CP symmetry. Direct CP violation, on the other hand, occurs in the decay process itself, where the decay rate of kaons differs from that of antikaons.

The discovery of  CP violation in kaons gave birth to the idea that the universe might inherently favor matter over antimatter, offering a possible explanation for the observed matter-antimatter asymmetry.

While CP violation in the kaon system is a step towards understanding the matter-antimatter imbalance, it alone is not sufficient to account for the observed dominance of matter. The degree of CP violation observed in kaons is too small to explain the vast difference.

The discovery of CP violation was a profound milestone, but it also left many questions unanswered. Why does CP violation occur? Are there other, more significant sources of CP violation in the universe? Could these be the key to solving the matter-antimatter puzzle?

The subatomic world is where physicists continue to explore, and they are trying to solve the puzzle of the beginnings of Earth. The strange quarks and their role in CP violation offer us a look at the subtle powers that have influenced our universe. Nevertheless, each finding we make pushes us towards comprehending what reality is, even if everything has not been explained by a given theory.

That’s it for this episode, I hope it helps you in continuing your exploration of the fascinating world of antimatter. In the next episode, we will dive deeper into the Low Energy Antiproton Ring (LEAR) at CERN and its aim of manufacturing antihydrogen, so stay tuned!