In 2018, the Large Hadron Collider ran a special data-taking campaign: the CMS detector captured proton collisions at breakneck speed to collect ten billion particles containing a beauty quark. These particles, B mesons, live for tiny fractions of a second and decay into lighter particles, like an overloaded train shedding cars on the move.
The Standard Model predicts how often different types of B mesons should be produced, but precise measurements are needed to check those predictions. Scientists from the CMS collaboration measured how many B+, B0, and B0s mesons are produced — three varieties that differ in which light quark sits next to the beauty quark. They found that the ratios of their yields change depending on the energy and angle at which the particle is emitted.
To obtain these numbers, physicists used two decay modes of B mesons: decays into particles with a charm quark (visible as showers of ordinary particles) and decays into particles containing J/ψ (which leave a clear signature of two muons). By comparing both modes, they also refined how often B mesons choose one decay path over the other.
A test of isospin symmetry, the idea that protons and neutrons should behave identically in strong interactions, showed that within measurement precision, the symmetry holds. This is another brick in the foundation of our understanding of how quarks assemble into particles.
B mesons contain a beauty quark that is four times heavier than a proton, yet they live only about one and a half picoseconds — in that time, light travels less than a millimeter.
In the series 'Star Trek,' 'quark' technologies are mentioned, but real B mesons are too short-lived to fuel a warp drive.