partonniveau

Partonniveau, literally “parton level” in Dutch, is a term used in high-energy physics to denote the description of a hadronic state in terms of its partons (quarks and gluons) at a given resolution scale. It is a foundational concept in the parton model and in perturbative quantum chromodynamics (QCD), where the internal structure of hadrons is encoded in parton distribution functions (PDFs). The partonniveau refers to the regime in which the scattering process is described by hard, short-distance parton interactions, with long-distance effects absorbed into PDFs or fragmentation functions.

In practical applications, the partonniveau is the stage at which the perturbative calculation of a partonic subprocess is performed. After the hard scattering, parton showering and hadronization take place, producing observable hadrons. Thus, predictions are often presented at the partonniveau and then evolved to hadron level using showering and hadronization models. The distinction is important for comparing theoretical calculations with experimental data.

Key related concepts include factorization, the factorization theorem, and the separation of scales: the PDFs depend on the factorization scale μF and the strong coupling runs with the renormalization scale μR. The partonniveau is central to the interpretation of collider cross sections, such as those at the LHC, where the measured jets and hadrons are related back to underlying partonic processes.

See also: parton distribution function, factorization, DGLAP evolution, parton shower, hadronization.