Wednesday, March 14, 2018

Why are all force particles bosons?


All of the force-particles in the standard model are bosons, now my question is pretty short, namely:




Why are all force particles bosons?



This can't be a coincidence.



Answer



The simplest Feynman diagram for an interaction between two particles looks like a letter "H". The cross-bar is a force-carrier being exchanged. At each vertex, you have a particle either emitting or absorbing a force-carrier. If the force-carrier has a half-integer spin, then you can't emit or absorb it without violating conservation of angular momentum. For example, an electron can't emit a spin-1/2 particle, because you can't couple spin 1/2 and spin 1/2 to make spin 1/2.


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