Gras, P.Höche, S.Kar, D.Larkoski, A.Lönnblad, L.Plätzer, S.Siódmok, A.Skands, P.Soyez, G.Thaler, J.2017-11-082017-11-082017-07Gras, P. et al. 2017. Systematics of quark/gluon tagging. JOURNAL OF HIGH ENERGY PHYSICS 2017(7), Article number 91.1126-6708 (Print)1029-8479 (Online)http://hdl.handle.net/10539/23387By measuring the substructure of a jet, one can assign it a “quark” or “gluon” tag. In the eikonal (double-logarithmic) limit, quark/gluon discrimination is determined solely by the color factor of the initiating parton (CF versus CA). In this paper, we confront the challenges faced when going beyond this leading-order understanding, using both parton-shower generators and first-principles calculations to assess the impact of higher-order perturbative and nonperturbative physics. Working in the idealized context of electron-positron collisions, where one can define a proxy for quark and gluon jets based on the Lorentz structure of the production vertex, we find a fascinating interplay between perturbative shower effects and nonperturbative hadronization effects. Turning to proton-proton collisions, we highlight a core set of measurements that would constrain current uncertainties in quark/gluon tagging and improve the overall modeling of jets at the Large Hadron Collider.en© 2017. The Author(s). This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0).JetsQCD PhenomenologyEVENT SHAPE DISTRIBUTIONSQCD ANALYTIC PREDICTIONSGLUON JET PROPERTIESQUARK JETSHERWIG PLUSPOWER CORRECTIONS3-JET EVENTSPARTONDIPOLETESTSArticle