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7 months ago in Particle Physics , Physics By Prachi Patil

Why can massless elementary particles not carry electric charge?

While studying gauge theories and the Standard Model, I’ve learned that photons and gluons are massless and neutral, while charged particles like electrons have mass. Is this a deep theoretical necessity or a contingent fact? What underlying principle perhaps from relativity or quantum field theory forbids this combination?

 

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By Rhetamed Answered 3 months ago

This isn't a coincidence; it's a cornerstone of our gauge theories. In my research on fundamental interactions, the key is gauge invariance. A massless particle like the photon must travel at *c* and have infinite range. If it carried electric charge itself, it would self-interact continuously via its own electromagnetic field. This would violate local U(1) gauge symmetry, which requires the force carrier to be neutral. Essentially, the theory’s mathematical consistency not just observation demands this separation.

 

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