Free Fractionally Charged Particles

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Discussion Overview

The discussion revolves around the possibility of free fractionally charged particles within the framework of the standard model of particle physics. Participants explore the implications of charge conservation, the role of color charge in binding particles, and the conditions necessary for anomaly cancellation.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that while fractionally charged particles exist, they are always confined within composite particles of integer charge due to color charge constraints in quantum chromodynamics (QCD).
  • Others argue that introducing a free fractionally charged particle would lead to inconsistencies, as the total charge must sum to zero, necessitating the existence of a partner particle with an equal and opposite charge.
  • A participant notes that free quarks can exist at high energies, suggesting that the observation of only integer-quantized charges may be an experimental limitation rather than a theoretical one.
  • Another participant emphasizes the importance of charge conservation, stating that adding a new particle with charge q requires a corresponding particle with charge -q, along with their antiparticles.
  • Some contributions highlight the chaotic nature of particle mass quantization, with varying mass scales for different quarks and leptons.
  • One participant mentions the requirement for anomaly cancellation, referencing specific conditions that must be satisfied across all particles and antiparticles.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of free fractionally charged particles, with some supporting the idea that such particles cannot exist independently due to charge conservation laws, while others question whether this is a theoretical limitation or an observational one. The discussion remains unresolved regarding the implications of these points.

Contextual Notes

Limitations include the dependence on the definitions of charge and color charge, as well as the unresolved nature of certain mathematical conditions related to anomaly cancellation.

stevendaryl
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It is intriguing (to me) that while fractionally charged particles exist in the standard model, they are always bound into composite particles of integer charge. The standard model explains this by QCD: fractionally charged particles all have nonzero color charge, and so can't be free. But I'm wondering whether it would be possible to introduce a fractionally charged free particle, or whether the theory becomes inconsistent in that case. Is there some deep reason that colorless particles must have integral charge, other than the fact that the standard model carefully assigns color and electric charges to make this happen?
 
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You can't do this by itself. The sum of the charges under all forces for all particles (not antiparticles) must be zero. So if you create a Q=4/3 "fatlectron", there needs to be a Q=-4/3 partner, *plus* their antiparticles.
 
Vanadium, if it's not antiparticles, than what's the partner of the electron?
But that is actually weird for me...since you can have free quarks [fractional charged particles] at high energies[temperatures] as for example in the Quark-Gluon Plasma... So it's not a matter of theory I guess, but a matter of observation tthat we get only integer-quantized charges.
The most intriguing particle quantization is their masses... :) so chaotic/irrational (eg from some MeV for the u,d up to 4 GeV for b and then a really high jump to 170GeV for t). And so on... especially if those particles are [maybe] one single thing...
 
The total charge for *all* the particles has to be zero. So you have 3 (colors) +2/3 quarks, and 3 -1/3quarks, and an electron -1, and that sums to zero. (x3 generations, and it still sums to zero). So if I add a new particle with charge q, I must at a minimum add a new particle of charge -q.

On top of that, there are antiparticles.
 
ChrisVer said:
The most intriguing particle quantization is their masses... :) so chaotic/irrational (eg from some MeV for the u,d up to 4 GeV for b and then a really high jump to 170GeV for t). And so on... especially if those particles are [maybe] one single thing...

You forgot: Electron 511 keV, neutrino sub-eV ... The last jump down is at least 5 orders of magnitude.

Also, Vanadium is not saying it right out, but he seems to be referring to (one of) the requirements for anomaly cancellation.
 
aha so I guessed, but I had misunderstood the requirement -for eg U[1]- \sum_{i} Y_{i}^{3}=0 for anomaly cancelation **, considering i running over everything [particles & antiparticles (or Left/Right reprs)- so in that case electron would cancel positron and so on].

**: which once summed over all particles gives the 1.3 condition here:
http://cds.cern.ch/record/439081/files/0005015.pdf

Vana's post thouggh referred to the next two...1,4 and 1.5..so I just didn't *remember* [or know] those conditions...
 
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