Cross Section Measurement of Associated $W^{\pm} + J/\psi$ Production in $pp$ Collisions at $\sqrt{s}=$ 13 TeV With the ATLAS Detector

The cross-sections of prompt and non-prompt production of $W^{\pm} + J/\psi$ are being measured by the ATLAS Collaboration using the full 13 TeV LHC Run II $pp$ collision data set. The prompt production of associated $J/\psi$ with a $W^{\pm}$, where both particles are produced in a single parton-parton interaction, provides constraints on models of non-relativistic quantum chromodynamics, especially in the realm of heavy quarkonia production. Additionally, this process can occur in double-parton scattering (DPS) interactions, and that measurement offers a clear test of DPS models. In this analysis, we emphasize the ability to separate the single-parton and double-parton production modes, in order to better understand each one. Finally, the non-prompt measurement allows for the study of top production and b-quark fragmentation.