Experimenting with Spinor Rotations & Sign Changes

[wnvl2]

When a spinor is rotated through 360◦, it is returned to its original direction, but it also picks up an overall sign change. This sign has no consequence when spinors are examined one at a time, but it can be relevant when one spinor is compared with another. Is there an experiment to make an electron interact with another electron that has a fase factor of -1 because of that 'rotation'?

 

[vanhees71]

I'm not aware that this phase factor has ever been experimentally observed for electrons, but there's a famous experiment with neutrons:

https://doi.org/10.1016/0375-9601(75)90798-7