quantum chromodynamics - Could the fractional model of Quarks electric charge turn out to be false?

The delta baryons (also called delta resonances) are a family of subatomic hadron particles which have the symbols $\Delta^{++}$, $\Delta^{+}$, $\Delta^{0}$, and $\Delta^{−}$ and electric charges +2, +1, 0 and −1 elementary charge respectively.

"existence of the $\Delta^{++}$, with its unusual +2 electric charge, was a crucial clue in the development of the quark model."

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  , three same quarks $\Delta^{++}=uuu$, and two electric charge, isn't it impossible?!.

  
  


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  Could the fractional model of Quarks electric charge turn out to be false? (leptons don't have fractional electric charge)

  
  

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Quarks do not exist. Everything is made up of positrons and electrons

All real free particles have a charge of -1 , 0, +1 - only quarks have fractional charges which I find unncessary since all particles could be made up of whole charge positrions and electrons. Can anyone cite a particle that could not be made up of positrons/electrons and must be made up of 1/3 charge fraction quarks?"

Fractional Electric Charges were not proposed by QCD, but by the quark model, which came beforehand.

QCD offered a number of inconclusive predictions, such as Color Force and Fractional Electric Charges, Wrong. Fractional Electric Charges were not proposed by QCD, but by the quark model, which came beforehand.

On the breakdown of Quarks fractional electric charge values.

this "thought" that Quarks have a fractional electric charge values may not be true!. according to ahmad reza estakhr research in the field of QCD (Quantum Chromo Dynamics) three times the elementary charge (depending on flavor) Up, Charm and Top Quarks (called Up-Type Quarks) have electric charge of zero! 0 (Which means Up- Type Quarks are uncharged ), while Down, Strange and Bottom Quarks (called Down- Type Quarks) just Could have a electric charge of plus or minus one! (+1, -1) in estakhr's model down-type Quarks are results of electroweak interaction between charged leptons and anti leptons and Up-type Quarks, and this is the reason that Quarks do not have fractional electric charge values. Which means charge of hadron is not the sum of the charge of its constituent quarks, it is just sum of the charge of Down-Type Quarks..."

Nuclear Forces – part 2

In the early 1960’s when a physicist by the name of Murray Gell-Mann put forward the hypothesis for the existence of quarks, he speculated that the charge of an up quark was two thirds of a proton’s, and the down quark was one third of an electron’s charge. In this way a proton consisting of two ups and one down quark would have a charge of +2/3 +2/3 -1/3 = +1. The benefit of such fractional charges is that a neutron could then be said to consist of two downs and one up quark, giving it a net charge of -1/3 -1/3 +2/3 = 0; i.e. a neutral charge. I would suggest that this neutron model must surely be wrong. We know that a neutron decays into a proton and electron. For this model to be correct, it would require that a down quark transform itself into an up quark – changing both its charge type and strength from -1/3 to +2/3 – and that an electron essentially be produced from nowhere! Perhaps this is possible but a simple ‘neutron = proton + electron’ model seems far more likely...."

here is the solution:

If anyone can disprove the existence of three triplets of quarks for $u,u,u \neq \Delta^{++}$ or prove that $\Delta^{++}$ have electric charge of zero then fractional model of Quarks electric charge will breakdown!.

Answer

The "resources" linked in the post are bad. But there was a time when serious people were interested in the possibility that quarks have integer charges. Han and Nambu introduced the idea, Pati and Salam made a gauge theory of it, Witten suggested how to test it, and this was done at CERN in the 1980s (see page 11). There would be several ways in which the charge of the quarks can show up experimentally (but I don't know a good review), and to maintain the integer-charge theory now, you would need extra new physical effects to explain all the measurements consistent with fractional charge.

Psychological resistance to the idea of fractionally charged quarks probably has two sources: 1) fractions just feel unnatural 2) the quarks always combine into integer-charged hadrons. For 1), the pattern of charges in the standard model can be explained in grand unified theories. For 2), given these charges, the allowed color singlet states in QCD all have integer charge, since they are made of quark-antiquark and/or quark-quark-quark combinations, and those elements only have integer charge. But I feel there ought to be a deeper explanation for 2).