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I am studying elementary particle physics and I am wondering what a parton level Feynman diagram is? My understanding is that partons are representations of the quark and gluon substructure of hadrons, and so I am assuming that any diagram that has a quark or gluon qualifies as a parton-level diagram, but I cannot find any reference to it in my notes or online.

Could anyone explain (with examples preferably), what a parton-level Feynman diagram is?

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The parton model was proposed by Feynman before the existence of quarks and gluons within the proton was established experimentally:

In particle physics, the parton model was proposed by Richard Feynman in 1969 as a way to analyze high-energy hadron collisions.

At that time the parton model was set up as a uniform distribution of partons within the nucleon, and calculations and a model were proposed to explain scattering crossections. Deep inelastic experiments showed that there existed a hard core in the nucleus, disagreeing with the predictions of the parton model. The accumulation of such data by several experiments identified the cores as quarks which had already been proposed by the SU(3) representations of the hadronic resonances.

It was later recognized that partons describe the same objects now more commonly referred to as quarks and gluons. Therefore a more detailed presentation of the properties and physical theories pertaining indirectly to partons can be found under quarks.

So at this stage the Feynman parton diagrams will be identical to the interactions of quarks and gluons according to the problem at hand.

gluon diagram enter image description here

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