Author(s)
| Gras, Philippe (IRFU, Saclay) ; Höche, Stefan (SLAC) ; Kar, Deepak (Witwatersrand U.) ; Larkoski, Andrew (Reed Coll.) ; Lönnblad, Leif (Lund U. ; Lund U., Dept. Theor. Phys.) ; Plätzer, Simon (Durham U. ; Durham U., IPPP ; Manchester U.) ; Siódmok, Andrzej (CERN ; Cracow, INP) ; Skands, Peter (Monash U.) ; Soyez, Gregory (IPhT, Saclay) ; Thaler, Jesse (MIT, Cambridge, CTP) |
Abstract
| By 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 (C_F versus C_A). 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. |