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.A photon is a fundamental particle of light that carries energy and has no electric charge or rest mass.
Based on current scientific understanding and measurements of helicity values, a photon is believed to have no rest mass. However, there is ongoing research and debate about the possibility of a very small rest mass for photons.
The rest mass of a photon cannot be directly measured, as it is believed to be zero. However, scientists can indirectly measure the mass by studying the helicity values of photons and their interactions with other particles.
Helicity values refer to the intrinsic angular momentum of a particle, specifically the direction of spin relative to its direction of motion. For a photon, helicity values can provide information about its mass and other properties.
Understanding the rest mass of a photon is important for furthering our understanding of the fundamental properties of light and other particles, as well as for developing new technologies and applications in fields such as quantum mechanics and telecommunications.