The discussion revolves around the possibility of determining whether a photon has a non-zero rest mass based on measured helicity values. It touches on concepts from particle physics, particularly in relation to helicity and chirality in quantum field theory (QFT).
Participants generally agree on the massless nature of photons in the context of QFT and helicity, but the discussion remains exploratory without a definitive conclusion on the implications of helicity measurements for a photon's rest mass.
Participants express varying levels of familiarity with QFT concepts, and there are assumptions about the applicability of helicity arguments to photons that remain unexamined.
Students and individuals interested in particle physics, particularly those studying helicity, chirality, and the properties of photons in quantum field theory.
rayveldkamp said:
) mixes up the two different possible chiralities. This is a result of the famous "tau-theta-puzzle" in QFT. To make a long story short : in QFT all elementary particles are massless because the two chiralities each correspond to a different kind of fundamental "particle-property". I mean, in QFT particles are classified based upon their chirality because a left handed chiral particle does not behave in the same way as a right hand chiral particle. So mass has to be zero (before the spontaneous breakdown of symmetry) because otherwise one particle possesses the TWO chiralities at once (because of the mass-term in the Lagrangian) and thus it is NOT fundamental. So basically photons are always massless because they do not interact with the Higgs-field. They contain a distinct chirality-value and thus not different values for ONE photon. Just look at the V-A-current in the elektroweak-theory : only left handed fermions (or right handed anti-fermions) are involved in weak charged currents.