Final answer:
The lack of conservation of the baryon number, as predicted in certain proton decay processes, gives a plausible explanation for the matter dominance in the universe. This violation would have allowed for slight excess of matter over antimatter after the Big Bang, leading to the matter we observe in the universe after mutual annihilation.
Step-by-step explanation:
The association between the conservation of baryon number and the dominance of matter over antimatter in the universe is rooted in the asymmetries observed in particle physics. Current theories, including Grand Unified Theories (GUTs), suggest that proton decay, while extremely rare, is possible and would indicate the violation of baryon number conservation.
If such a process took place in the early universe, it could have led to an excess of matter over antimatter. This excess is what remains after matter and antimatter annihilated each other, eventually leading to the formation of the stars and galaxies we observe today. The observed instability of protons, with a decay that does not conserve baryon number, helps to explain why there is more matter than antimatter in the universe.
Particle physics experiments have shown slight asymmetries, like the decay of neutral K-mesons, which create more matter than antimatter. This asymmetry would have been more pronounced in the conditions present shortly after the Big Bang, leading to slightly more matter particles being produced than antimatter particles. Over time, as matter and antimatter annihilated each other, the residual matter would persist, giving rise to matter-dominated universe we see today.