When using two component notation people often prefer to refrain from using arrows in Feynman diagrams to denote charge flow as is done in four-component notation. Instead, if understand correctly, they use arrows to denote chirality. I'd like to know what is the prescription to draw out the diagrams. I have read here (pg. 39) that
arrows indicate the spinor index structure, with fields of undotted indices flowing into any vertex and field of dotted indices flowing out of any vertices
(see the reference above for many examples).
However, trying this out on Majorana and Dirac mass terms, this doesn't seem to be correct. A Majorana mass term, $\psi ^\alpha \psi_\alpha +h.c.$, is thus composed only of undotted indices. With the reasoning above, it should have two arrows pointing into the vertex,
However, I'm pretty sure that this is a Dirac mass, and not a Majorana mass. What am I missing?
This post imported from StackExchange Physics at 2014-04-01 16:06 (UCT), posted by SE-user JeffDror