QCD Reference Frames and False Jet Individualism

In collider physics we measure the sprays of hardrons as a proxy for quarks and gluons. We call these sprays jets. The properties of hadronic jets are often measured as a function of their lab-frame momenta. This view is overly simplistic because jet fragmentation must occur in the particular rest frame of all color-connected particles. Jets are better thought of as process dependent, meaning that their fragmentation depends are how they were produced. This non-factorizability of jets has consequences for jet techniques such as jet tagging, boosted boson measurements, and searches for physics Beyond the Standard Model.