Because of its forward coverage, LHCb can probe the valence quark distributions of protons and nuclei at small and large Bjorken-x with high precision. This proceeding presents new LHCb measurements of Z boson production in association with charm jet in the forward region of proton-proton collisions and Z boson production in proton-lead collisions. Z+charm jet production could be sensitive to a valence-like intrinsic-charm component in the proton wave function. The measurements of Z production in proton-lead collisions provide new constraints on the partonic structure of nucleons inside nuclei. Comparisons between the results and calculations with parton distribution functions are also discussed.

6 pages, 7 figures, Quark Matter 2022 Proceedings, https://indi.to/5XBNH