Physicists have confirmed a new mismatch between matter and antimatter

Charge-parity violation occurs in a class of particles called baryons 

Two protons (indicated with p’s) collide at the LHCb experiment, producing a lambda-b baryon comprised of three quarks — dubbed up (u), down (d) and bottom (b) — that decays into various other particles (colored lines).

LHCb collaboration/arXiv.org 2025

There’s a newfound mismatch between matter and antimatter. And that could bring physicists one step closer to understanding how everything in the universe came to be.

For the most part, particles and their oppositely charged antiparticles are like perfect mirror images of one another. But some particles disobey this symmetry, a phenomenon known as charge-parity, or CP, violation. Now, researchers at the Large Hadron Collider near Geneva have spotted CP violation in a class of particles called baryons, where it’s never been confirmed before. 

Baryons are particles that contain three smaller particles called quarks. The most famous examples of baryons are protons and neutrons. Previously, scientists had seen CP violation only in mesons, which are particles containing one quark and one antiquark.

For the new study, researchers with the LHCb collaboration studied particles called lambda-b baryons. The scientists looked at a decay of a lambda-b baryon into a proton and three lesser-known particles: a kaon and two pions. The rate of this decay is slightly different than that of its antimatter counterpart, the team found. This difference indicates CP violation, the researchers report in a paper submitted March 21 to arXiv.org and in a March 25 talk at the Rencontres de Moriond meeting in La Thuile, Italy.

Building on previous hints of CP violation in baryons, the study is the first to cross the statistical threshold for a discovery, known as five sigma.

A better understanding of CP violation could help explain how matter came to dominate over antimatter. In the Big Bang, matter and antimatter were made in equal measure. CP violation is thought to have given matter the upper hand. But known processes don’t violate CP enough to account for the matter-antimatter imbalance. The new study doesn’t solve that quandary, but it’s a step in the right direction.

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