Karapınar, Güler2021-01-242021-01-2420101434-60441434-6052https://doi.org/10.1140/epjc/s10052-010-1453-9https://hdl.handle.net/11147/9697A measurement of the underlying activity in scattering processes with p (T) scale in the GeV region is performed in proton-proton collisions at root s = 0.9 TeV, using data collected by the CMS experiment at the LHC. Charged particle production is studied with reference to the direction of a leading object, either a charged particle or a set of charged particles forming a jet. Predictions of several QCD-inspired models as implemented in PYTHIA are compared, after full detector simulation, to the data. The models generally predict too little production of charged particles with pseudorapidity |eta|< 2, p (T) > 0.5 GeV/c, and azimuthal direction transverse to that of the leading object.eninfo:eu-repo/semantics/openAccessArticle10.1140/epjc/s10052-010-1453-910.1140/epjc/s10052-010-1453-9