Hadronic structure in high-energy collisions

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Parton distribution functions quantify the nonperturbative QCD structure of protons and nuclei, expressed as probabilities for finding quarks and gluons, in high-energy collisions. Determined by applying advanced quantum field theory to precise experimental measurements using modern statistical techniques, parton distribution functions are crucial for interpreting the short-distance behavior of the standard model. This review presents the state of the art of this evolving subject.