The conversion of a single photon into a particle-antiparticle pair is a process that can occur under certain conditions in the presence of a sufficiently strong electromagnetic field. This process is known as pair production. The most common example of pair production is the creation of an electron-positron pair from a photon in the presence of a nucleus or another charged particle.
Pair production requires the conservation of energy and momentum. In order for this process to occur, the energy of the photon must be sufficient to create a particle-antiparticle pair. This energy requirement is dictated by Einstein's equation, E=mc², where E is the energy, m is the mass of the particle, and c is the speed of light. If the energy of the photon is greater than or equal to the combined rest mass of the particle-antiparticle pair, pair production can take place.
As for the slightly greater production of particles compared to antiparticles, this phenomenon is known as the matter-antimatter asymmetry problem. The observed universe is predominantly composed of matter, while antimatter is relatively rare. The exact reason for this imbalance is not yet fully understood and remains an active area of research in particle physics.
One of the proposed explanations for the matter-antimatter asymmetry is a process called baryogenesis, which involves violations of certain fundamental symmetries in the early universe. It is thought that during the early stages of the universe, there were slight differences in the behavior of matter and antimatter that led to a small excess of matter over antimatter. This imbalance then became amplified as the universe expanded and cooled.
However, the specific mechanisms behind baryogenesis and the precise reasons for the matter-antimatter asymmetry are still subject to ongoing scientific investigation. Researchers are conducting experiments and theoretical studies to better understand these fundamental questions about the nature of our universe and the origin of the matter-antimatter imbalance.