The universe should be empty of matter, but it isn't.
In short: According to our most fundamental laws of physics, the Big Bang should have produced equal parts matter and antimatter. If that were true, they would have annihilated each other completely, leaving a universe of pure radiation. Instead, we exist in a world dominated by matter. Why did one side win?
The discrepancy between theory and reality is rooted in Einstein’s equation E=mc² and the Big Bang theory. Together, these pillars of modern physics predict that matter and antimatter should have been created in perfectly balanced quantities. However, the observable universe is composed almost entirely of matter. This imbalance suggests a fundamental asymmetry in how subatomic particles behave—a mystery that physicists have sought to solve for decades.
A key mechanism behind this potential imbalance is known as charge–parity (CP) violation. This effect describes a situation where the laws of physics do not treat matter and antimatter identically. While CP violation was predicted by the Standard Model of physics, it was first experimentally observed in mesons—particles made of two quarks—more than 60 years ago. Because baryons (made of three quarks, like protons and neutrons) make up the bulk of visible matter, finding evidence of this asymmetry in them is critical.
In a recent breakthrough published in Nature, researchers from the LHCb experiment at CERN reported the first-known observation of CP violation in decaying composite subatomic particles belonging to the baryon class. By analyzing data from proton–proton collisions, Xueting Yang and colleagues identified specific differences in behavior between baryonic matter and antimatter. While this discovery does not fully explain why matter dominates the cosmos, it provides a vital experimental clue for searching for physics beyond the Standard Model.
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Sources
- Summary by Intellect · source: 24 Subatomic Stories: Where's all the antimatter?
- Also: Subatomic Stories: Where’s all the antimatter?
- Also: Where did all the antimatter go? This mismatch in how subatomic particles behave could hold a clue
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