Fig. 2: Intrinsic charm and Z + charm production at LHCb.
Top left, the LHCb measurements of Z-boson production in association with charm-tagged jets, \({{\mathcal{R}}}_{{\rm{j}}}^{{\rm{c}}}\), at \(\sqrt{s}=13\,\mathrm{TeV}\), compared with our default prediction, which includes an intrinsic charm component, as well as with a variant in which we impose the vanishing of the intrinsic charm component. The thicker (thinner) bands in the LHCb data indicate the statistical (total) uncertainty, while the theory predictions include both PDFU and MHOU. Top right, the correlation coefficient between the charm PDF at Q = 100 GeV in NNPDF4.0 and the LHCb measurements of \({{\mathcal{R}}}_{{\rm{j}}}^{{\rm{c}}}\) for the three yZ bins. The dotted horizonal line indicates the maximum possible correlation. Centre, the charm PDF in the 4FNS (right) and the intrinsic (3FNS) charm PDF (left) before and after inclusion of the LHCb Z + charm (c) data. Results are shown for both experimental correlation models discussed in the text. Bottom left, the intrinsic charm PDF before and after inclusion of the EMC charm structure function data. Bottom right, the statistical significance of the intrinsic charm PDF in our baseline analysis, compared to the results obtained also including the LHCb Z + charm (with uncorrelated systematics) or the EMC structure function data, or both. The dotted horizontal line indicates the 3σ threshold.
