In a paper submitted to the journal Physical Review Letters, the researchers propose a new mechanism that generates slightly different masses for the proton and antiproton, which allowed the Universe to evolve toward a state containing much more matter than antimatter.
"Many models have been proposed to explain this mystery, but the problem with the vast majority of these models is that they require conditions in the early Universe that don't have any obvious explanations," said Hitoshi Murayama, a UC Berkeley professor of physics. "In our work, we found that a simple and very well-motivated mechanism naturally arises from a widely-studied and well-known extension of the standard model, called Supersymmetry."
According to the Standard Model of Physics, all matter is made up of subatomic particles called quarks and leptons, and the forces that act between these particles are mediated by bosons. The Standard Model also predicts the existence of antiparticles for each of these particles, which have the same mass as their corresponding particles but opposite electric charge.
In the early universe, it is thought that particles and antiparticles were created in equal amounts. However, within a tiny fraction of a second, the vast majority of these particles and antiparticles annihilated each other, leaving behind a small excess of matter. This excess of matter is what eventually formed the galaxies and stars that we see in the universe today.
The researchers found that the Supersymmetric version of the Standard Model naturally leads to a small difference in mass between the proton and antiproton. This mass difference is sufficient to allow the universe to evolve toward a state containing much more matter than antimatter.
In the Supersymmetric model, the proton and antiproton are hypothesized to be made up of three quarks, one of which is a heavy "supersymmetric quark" that is unique to the Supersymmetric model. The researchers propose that the interaction between heavy quarks and the Higgs particle could generate the mass difference between proton and antiproton.
"The mechanism that we propose requires only a very small modification of the Standard Model, which is quite compelling from a theoretical point of view," said Murayama. "Our next step is to see whether our proposal is consistent with various experimental data such as those obtained by the LHC at CERN."
If the researchers' proposal is correct, it may provide a partial explanation for the great mystery of why the universe has less antimatter than matter. It could also provide insights into the nature of supersymmetry, a theory that has been widely studied in physics but has yet to be experimentally confirmed.
