2026/06/04 by LHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb +1187 · 2 voices
#hep-ex
This letter reports a study of associated Z boson and prompt J/ψ production in proton-proton collisions at √(s)=13 TeV with the LHCb detector in the forward rapidity region, using a data sample taken during 2016 to 2018 corresponding to an integrated luminosity of 5.1 fb-1. The measured fiducial cross-section is 5.5 ± 1.5 pb, significantly exceeding the single-parton scattering expectation of 0.10 ± 0.08 pb, indicating that multiparton interactions dominate this process in the explored phase space. Interpreted within the standard double-parton scattering framework, the data yields an effective cross-section σeff = 16.6 ± 4.7 mb. This provides a direct experimental constraint on the transverse spatial structure of the proton in a kinematic regime characterized simultaneously by small Bjorken-x and an electroweak hard scale set by the Z boson mass.