Speaker
Description
The simultaneous production of a $W^\mp$ boson and a charmed hadron $D^{(*)\pm}$ in proton-proton collisions, recently measured by ATLAS at $\sqrt{s} = 13$ TeV, offers a potential probe for constraining the strange quark distribution and studying strangeness asymmetry. By considering the production ratio of oppositely charged mesons, scale and fragmentation uncertainties become negligible. We present results for this ratio as functions of $p_T$ of the meson and $\eta$ of the charged lepton from the $W^\mp$ decay, computed using NLO general-mass perturbative QCD with scale-dependent fragmentation functions and three different PDF sets. The analysis shows good agreement between the ATLAS data and the CT18A and MSHT20 PDFs. In contrast, a significant tension is found for NNPDF40, with $\chi^2 / \#\text{d.o.f.} \approx 4$. Interpretation of the results proves difficult: on one hand, reweighting of MSHT20 indicates an increase in the magnitude of the strangeness asymmetry across most of $x$ space, while on the other hand, CT18A contains no strangeness asymmetry to begin with. In addition, we find that the ATLAS kinematic region is not sufficient to constrain the intrinsic charm contribution in protons using the $W^\mp D^{(*)\pm}$ events. Finally, we discuss the feasibility of measuring $W^\mp D^{(*)\pm}$ production in proton-lead collisions.
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