Strong force & gluons
Predict firstWhat is the cloud around the three markers? Is a proton just three little balls?
Understand why pulling quarks apart normally makes new hadrons instead of freeing a quark.
Prerequisites: Atomic nuclei contain protons and neutrons, which contain quarks. Here u means up quark and d means down quark; a bar denotes an antiparticle, and Q a heavy quark. Watch first; the formulae can come later.First, enter a proton
Predict firstWhat is the cloud around the three markers? Is a proton just three little balls?
The u, u, d markers denote the proton’s three valence quarks: its net quark content. A real proton also contains gluons and a dynamic quark–antiquark sea. The cloud suggests spatial field structure and the filaments emphasise concentrated regions; they are not countable gluon orbits. Quarks have no observed surfaces or sizes like these enlarged markers. Drag to orbit and become familiar with the structure.
How to observe
- Follow a two-colour pulse: colour changes, quark flavour does not.
- Stretch the flux tube and follow external work into field energy and new hadrons.
- Explore a three-gluon vertex and weaker coupling at higher energy scales.
Model notes
A colour-flow and effective-string teaching model, not real-time lattice QCD or a photograph of a proton. Positions, sizes, Y-shaped structure, filaments, pulses and seconds of animation are illustrative. Colours label basis components; singlets require quantum superpositions. Stretching accounts for Efield = σr and external work. The illustrative pair/hadronisation budget is not a bare quark mass; the smooth transition is not a quantum production probability. Further separation of the two final clusters is for display, with no unaccounted kinetic-energy claim. The heavy–light mesons show colour structure, not a predicted hadron spectrum. The three-gluon junction is a vertex within a process, not a free on-shell gluon decay. Fixed-five-flavour one-loop coupling is used only from 10 to 150 GeV, never extrapolated into confinement. Ordinary low-temperature hadron confinement cannot be applied unchanged to quark–gluon plasma. The residual nuclear interaction between nucleons is related to QCD but is not this same flux tube.