What is a "Born diagram"?

Question

In the introduction of this article, the following statement is made regarding the partonic picture for hadronic scattering amplitudes:

To leading order in $\alpha_S (Q^2)$, the "hard-scattering amplitude" $T_H$ is the sum of all Born diagrams for $\gamma^*+3q\rightarrow 3q$ in perturbative QCD.

In the above, $T_H$ is the scattering amplitude for $\gamma^*+3q\rightarrow 3q$ where each quark $q$ is specified. Of course, it is given by the sum of all Feynman diagrams contributing to it. At $O(\alpha)$ we only have tree-level diagrams, and therefore I believe "Born diagrams" should mean either "tree-level Feynman diagrams" or "tree-level partonic Feynman diagrams".

Are either of these guesses correct? What exactly is a "Born diagram"? I would appreciate any references.

Answer 1

You're right. A "Born" and "tree level" are the same thing. It's not very common to say Born anymore, but the reason why the call it like that in the reference is likely due to the more standard quantum mechanical definition. In nonrelativistic quantum mechanics one usually calls the "Born approximation" as the approximation at lowest order in the small potential.

You can see pretty much every quantum mechanics books (say, Weinberg's "Lectures on Quantum Mechanics") when the scattering off a potential is treated.