Improving quark flavor separation with forward $W$ and $Z$ production at LHCb

We quantify the constraints on the flavour separation between the quarks and antiquarks in the proton provided by the recent forward weak gauge boson production data from the LHCb experiment at $\sqrt{s}=7$ and 8 TeV. Performed in the framework of the NNPDF3.1 global analysis, this study highlights the key role that the LHCb W and Z data have in achieving a robust quark flavour separation in the large-x region, including the strange and charm quarks. We demonstrate how the LHCb measurements lead to improved determinations of the the up and down quark PDFs in the region $x\ge 0.1$, with an uncertainty reduction that can be as large as a factor 2. We also show how the LHCb forward measurements severely restrict the size of the fitted charm PDF at large x, imposing stringent constraints on non-perturbative models for the charm content of the nucleon.