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CP Violation PDF Print E-mail
Tuesday, 24 November 2009 02:18

As the Universe expands and cools and the process of creation and annihilation of matter/anti-matter pairs slows down. Soon matter and anti-matter has time to undergo other nuclear processes, such as nuclear decay. Many exotic particles, massive bosons or mesons, can undergo decay into smaller particles. If the Universe is out of equilibrium, then the decay process, fixed by the emergent laws of Nature, can become out of balance if there exists some asymmetry in the rules of particle interactions. This would result in the production of extra matter particles, rather than equal numbers of matter and anti-matter.

 

In the quantum world, there are large numbers of symmetric relationships. For example, there is the symmetry between matter and anti-matter. For every matter particle, there is a corresponding anti-matter particle of opposite charge. In the 1960's, it was found that some types of particles did not conserve left or right-handedness during their decay into other particles. This property, called parity, was found to be broken in a small number of interactions at the same time the charge symmetry was also broken and became known as CP violation.

  • CP violation is one such asymmetry which is only temporary in today's world, but during the rapid expanding early Universe these effects have larger effects
 The symmetry is restored when particle interactions are considered under the global CPT rule (charge - parity - time reversal), which states that that a particle and its anti-particle may be different, but will behave the same in a mirror-reflected, time-reversed study. During the inflation era, the rapid expansion of spacetime would have thrown the T in CPT symmetry out of balance, and the CP violation would have produced a small asymmetry in the baryon number.

This is another example of how quantum effects can be magnified to produce large consequences in the macroscopic world. CP violation, by itself, is not sufficient to resolve the matter/anti-matter assymetry. However, it is an example of what may be a class of reactions that produce more matter than anti-matter. The sum of these reactions explains the baryon number.

 


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