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In pure QCD in the confinement phase what happens if I add to a system of baryons, which are quarks in the condensed phase, another quark? It doesn't have any quark or antiquark to form a baryon or a meson so how does confinement work in this case?

Damiano
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    How can you add a single quark to the baryon when it's impossible to isolate a single quark? Where are you going to get that single quark from? Unless you can clarify exactly what reaction you are considering your question is impossible to answer. – John Rennie Jun 08 '18 at 06:43

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A quark has a color charge. This charge creates a strong attraction to another quark over a distance. The effect is similar to a string. Trying to pull two quarks apart is like stretching a string. You need to apply a force in tons to separate two quarks by a femtometer or $10^{-15}m$. So realistically your question distills to what happens if by applying enough energy we separate two quarks by a short distance? The answer is that the energy you supplied would end up creating two jets of hadrons. During this process the color string would remain between two color charged particles (not necessarily the original quarks). Once the kinetic energy is gone, the color string wins, and two color charged particles are pulled back together to either form a meson or annihilate.

Check this simple explanation of hadron jets: Higgs Boson - What are jets?

For more details: https://en.m.wikipedia.org/wiki/Jet_(particle_physics)

safesphere
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  • Yes, I knew that; the point is, if there are no quarks to couple to because they are all paired in color singlets what happens to the free quark? – Damiano Jun 10 '18 at 07:49
  • @Damiano The rules of the game are that a free quark cannot exist in this universe. Each quark is connected to another quark or anti-quark by a color string of gluons that cannot be broken or stretched beyond a femtometer. It is like asking, what happens with my shadow without me - it does not exist. – safesphere Jun 10 '18 at 08:07
  • @Damiano If a free quark magically appeared, it would not be able to form a color string to any remote quark, because such a string would have more energy than the quark has and thus violate energy conservation. Therefore a free quark would have to approach a bound quark at the distance of asymptotic freedom (where force changes from attraction to zero to to repulsion). In other words, a free quark would have to directly hit a proton or neutron and then possibly replace one of the quarks there and set that quark free. This is my speculation based on energy conservation, so take it with salt. – safesphere Jun 10 '18 at 08:36