I apologize if I mix metaphors. I'm trying to learn the language of quantum chromodymanics and I haven't found a good resource to clear my fuzzy thinking!

Are color charges for quarks:

1) Statically assigned to an individual quark for the duration of he existence of a proton or neutron.

2) A superposition of three color-charges which only manifest as 1-color=>1-quark at the time of measurement. In other words a form of triple-superposition.

3) Such that ccolors can spontaneously rotate from one quark to another.

I'm trying to find a good resource to begin studying the nature of quantum-chromodynamics and color charge to see if any superpositions exist in a nucleon.

1. can colour charge exist as superposition of quark states? This is not formulated correctly. A state can be a superposition of other states, not a charge. You are mixing pears with apples.

2. Can a quark be shared amongst hadrons? Answer is NO

Now on the colour

Colour charges are the sources and the receptors of the colour filed, like electric charge is for the electromagnetic field, but there are substantial differences

There are three different colour charges, red, blue and green (electric charge is one only). Each can be positive or negative (as the electric charge)

Both quarks and gluons have colour charges (photon instead is neutral)

A charged particle, e.g. an electron, in the vacuum polarizes the vacuum itself, producing virtual electron positron pairs around it. As a consequence the charge of the electron you measure depends on the distance from the electron you do that; it is lager if you go closer.

A quark polarises the vacuum in a similar way, but around it not only the virtual quark antiqaurk pairs are coloured, but also the gluons of the field. Consequently, the charge of the quark is larger at larger distances, and we cannot extract a quark from a proton; the colour force becomes too big. Quarks exist only in the hadrons, they are never free

As a consequence, we cannot directly measure the colour charge of a quark or of a gluon. Non the less both are perfectly defined by the theory, which provides the way to connect observables measured for the hadrons, to the colour charges inside them.

The issue is difficult however. The calculation of the observable meets integrals that diverge. There are mathematical methods to subtract the divergencies and to have a finite and precise final result. This is called renormalisation procedure. However there are different possible renormalisation schemes. The observables are for hadronic states, which have no colour. The different renormalisation schemes give the same result for the final non coloured states, but not necessarily for the coloured ones. The colour of a quark may depend on the renormalisation scheme adopted. But this does not mean that there are "superpositions". You cannot fully understand the situation if you do not study a quantum chromodynamics text book (after having the control of quantum field theory)

Alessandro,

Thank you for your patience and clear explanation. I know I have to eventually tackle textbook quantum chromodynamics, but the terminology comes up in other contexts so I am trying to correct as many of my fundamental misunderstandings as quickly as possible!

Quarks cannot be shared by hadrons because of the

property of "quark confinement". Because of this property

quarks can stay only within a hadron, which is mentioned

by Bettini.

This essentially means that strong interaction is a very short

range force.