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liucl78
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why massless particle, such as photon, can only have two helicity states?
Photon's helicity is 1,-1. Helicity zero is forbidden. why?
Photon's helicity is 1,-1. Helicity zero is forbidden. why?
liucl78 said:why massless particle, such as photon, can only have two helicity states?
Photon's helicity is 1,-1. Helicity zero is forbidden. why?
According to the theory of relativity, massless particles travel at the speed of light and therefore do not experience time. This means they cannot have a rest frame and can only have two possible directions of spin, resulting in two helicity states.
The two helicity states are left-handed and right-handed spin. Left-handed spin particles spin in the opposite direction of their momentum, while right-handed spin particles spin in the same direction as their momentum.
Helicity states and chirality are related, but not the same thing. Chirality refers to the asymmetry between left-handed and right-handed particles, while helicity states refer to the direction of spin of a particle. Massless particles can only have two helicity states, but they can have either left-handed or right-handed chirality.
No, massless particles cannot change their helicity states. This is because they travel at the speed of light and do not experience time, so they cannot rotate or change direction. Their helicity state is fixed and cannot be altered.
The number of helicity states affects how massless particles interact with each other and with other particles. For example, the weak nuclear force only affects left-handed particles, while the strong nuclear force only affects right-handed particles. This is due to the different interactions of the two helicity states with other particles.