Relationship between electron and quark charge

In summary, the coincidence of charges between electron and quark is a result of their being two different charges, which are more fundamental than the particles themselves. Grand unified theories offer an explanation for why these charges are related, but it is still an anomaly that they are not identical.
  • #1
a dull boy
40
1
Dear Physics Forum,

Is there any model where the electron and quark share a fundamental relationship, maybe in some string theory? I ask because it seems too much of a coincidence that two completely
independent particles would have a simple charge relationship of 1/3:1 .

Thanks, Mark
 
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  • #2
Cancellation of anomalies requires that the total charge in each generation of fermions must add up to zero. (Since they come in three colors, quarks must be counted with a weight of three.) Thus, up + down + electron + neutrino = 3(2/3) + 3(-1/3) + (-1) + 0 ≡ 0.
 
  • #3
Bill_K said:
Cancellation of anomalies requires that the total charge in each generation of fermions must add up to zero. (Since they come in three colors, quarks must be counted with a weight of three.) Thus, up + down + electron + neutrino = 3(2/3) + 3(-1/3) + (-1) + 0 ≡ 0.

Thanks for your response. I think I understand your statement - that theory requires the total charge in each generation to = zero, but I still don't understand why in fact (in an experimental sense) this is so. Why do the proton and electron have identical but opposite charges despite being made of very different things? It seems to coincidental to be a coincidence - meaning maybe they are related to each other in some more fundamental way.
 
  • #4
Grand unified theories can offer an explanation of this, by positing that quarks and leptons are the same at high energies but become different due to symmetry breaking at low energies. But relationships between these particles survive at low energies including simple ratios between their charges.
 
  • #5
Sure enough, many GUTs do contain constraints that relate the charge of different particles. And for a time, people thought that pursuing GUTs would turn out to be fruitful. Unfortunately they also contain a prediction about the rate at which protons decay, which experiment has failed to detect. While GUTs are an appealing idea, they fail to describe the world we live in, and are not at present a serious alternative to the Standard Model.
 
  • #6
a dull boy said:
Dear Physics Forum,

Is there any model where the electron and quark share a fundamental relationship, maybe in some string theory? I ask because it seems too much of a coincidence that two completely
independent particles would have a simple charge relationship of 1/3:1 .

Thanks, Mark

Maybe you look at it the wrong way round. Charges are more fundamental than elementary particles. So there are different combinations of charges. An electron is some value of electric charge in combination with zero of baryonic charge, while a quark is a non-zero combination of both charges.
 
  • #7
DrDu said:
Maybe you look at it the wrong way round. Charges are more fundamental than elementary particles. So there are different combinations of charges. An electron is some value of electric charge in combination with zero of baryonic charge, while a quark is a non-zero combination of both charges.

That is intriguing. I'd like to push on it a little. I agree that charge must be more fundamental than either quarks or leptons, I think that is what I'm trying to understand - if charge is more fundamental, then how are quarks related to leptons? The idea that BillK and The Duck referred to - that there are no leptons or baryons at high energies, and these particles result from symmetry breaking at low temperatures seems a satisyfing explanation.

There must be some issue at hand regarding charge being a component of both leptons and quarks, given the attempts to explain this through grand unified theories.
 
  • #8
a dull boy said:
That is intriguing. I'd like to push on it a little. I agree that charge must be more fundamental than either quarks or leptons, I think that is what I'm trying to understand - if charge is more fundamental, then how are quarks related to leptons? The idea that BillK and The Duck referred to - that there are no leptons or baryons at high energies, and these particles result from symmetry breaking at low temperatures seems a satisyfing explanation.

There must be some issue at hand regarding charge being a component of both leptons and quarks, given the attempts to explain this through grand unified theories.

Indeed , I would like to know that as well. A more in depth answer over why two fundamentally different particles share similar property of having a 'charge density' .
 

1. What is the relationship between electron and quark charges?

The relationship between electron and quark charges is that they both have a fundamental unit of electric charge, known as the elementary charge. The electron has a charge of -1, while quarks have charges of either +2/3 or -1/3. This means that electrons and quarks can interact with each other through electromagnetic forces.

2. How are the charges of electrons and quarks related to each other?

The charges of electrons and quarks are related through the concept of charge quantization. This means that the charges of these particles are always found in integer multiples of the elementary charge. For example, the charge of a proton is +1, which is equal to the sum of the charges of two up quarks (+2/3 + +2/3) and one down quark (-1/3). This relationship allows for the stability of matter.

3. Can electrons and quarks have different charges?

Yes, electrons and quarks can have different charges. The charge of an electron is always -1, but quarks can have either a charge of +2/3 or -1/3. This is due to the different types of quarks (up, down, charm, strange, top, bottom) and their respective charges. However, within a single particle, the overall charge must still be an integer multiple of the elementary charge.

4. How is the charge of an atom determined by the charges of its constituent particles?

The charge of an atom is determined by the charges of its constituent particles, which are protons, neutrons, and electrons. Protons and neutrons, which are made up of three quarks each, contribute to the overall charge of an atom. The number of protons in an atom determines its atomic number and therefore its overall charge. Electrons, which orbit the nucleus, have a negative charge that balances out the positive charge of the protons, resulting in an overall neutral charge for the atom.

5. Can the charge of an electron or quark change?

The charge of an electron or quark cannot change. As mentioned before, the charge of these particles is quantized and cannot be broken down into smaller units. This means that the charge of an electron will always be -1 and the charge of a quark will always be either +2/3 or -1/3. However, these particles can gain or lose electrons or interact with other particles, resulting in a change in their overall electric charge, but their fundamental charges will remain the same.

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