부산대학교 도서관

We provide a first quantitative indication that the wave function of the proton contains unequal distributions of charm quarks and antiquarks, i.e. a nonvanishing intrinsic valence charm distribution. A significant nonvanishing valence component cannot be perturbatively generated, hence our results reinforce previous evidence that the proton contains an intrinsic (i.e., not radiatively generated) charm quark component. We establish our result through a determination of the parton distribution functions (PDFs) of charm quarks and antiquarks in the proton. We propose two novel experimental probes of this intrinsic charm valence component: D-meson asymmetries in Z+c-jet production at the LHCb experiment, and flavor-tagged structure functions at the Electron-Ion Collider.
Comment: 11 pages, 11 figures. PDF files available for download in LHAPDF format from https://nnpdf.mi.infn.it/nnpdf4-0-charm-asymmetry-study/ Final version, to be published in PRD (letters). Figures 2, 6 and 7 added. Fit without imposing the charm valence sum rule added. Various small clarifications