Ivan Vujmilović, doc. dr. Luka Leskovec and prof. dr. Saša Prelovšek Komelj have, for the first time, calculated the internal structure of an exotic particle made of four quarks using ab-initio large-scale numerical simulations of quantum chromodynamics.
The study was done together with Sara Collins and publihsed in Phis. Rev. Lett.

The particle, known as the Tbb tetraquark, contains two bottom quarks and two light antiquarks; this combination cannot be described as a simple extension of conventional hadrons. By computing how this particle responds to electric and magnetic probes, the researchers determined how its electric charge is distributed. The results reveal a compact core formed by the two heavy b quarks, tightly bound together, surrounded by a lighter cloud of u and d antiquarks. Strikingly, the tetraquark is significantly smaller than a pair of mesons with the same quark content, indicating that it is a genuinely bound, novel form of matter rather than a loose molecular-like state.