# Does a vertex contribute (i e gamma ^ mu) if (e > 0) and (-i e gamma ^ mu) if (e < 0)

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Physisists seem to be divided in two layers: those who claim that vertices in Feynman diagrams contribute $+ i e \gamma ^ \mu$ and those who say $- i e \gamma ^ \mu$. As an example, Griffiths says $+$ and Schwartz says $-$. Quick Googling seems to indicate that the two layers are of the same size.

The difference could easily be due to the sign convention for $e$: do we have $e > 0$ or $e < 0$? Unfortunately, neither Griffiths nor Schwartz seem to reveal their respective sign conventions for $e$.

In general, sources tend to be silent about their sign convention of $e$. An exception is Kleinert who states $e \lt 0$ on Page 803 right after Equation (12.10) and says that vertices contribute $- e \gamma ^ \mu$ on Page 814 Equation (12.96).

My question is: does everyone agree that a vertex contributes $+ i e \gamma ^ \mu$ if $e > 0$ and $- i e \gamma ^ \mu$ if $e < 0$?

References:

Griffiths: "Introduction to Elementary Particles"

Schwartz: "Quantum Field Theory and the Standard Model".

Kleinter: "Particles and Quantum Fields" / http://users.physik.fu-berlin.de/~kleinert/b6/psfiles/Chapter-11-qed.pdf

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