A comprehensive study of perturbative and non-perturbative quantum chromodynamics in measurements of the underlying event and the transverse momentum of the Z boson with the CMS detector at the LHC

We explore the potential for an early measurement of the Z boson transverse momentum distribution in the muon decay channel for the first 10--100 pb-1 of the LHC data at 10 TeV collision energy. In this simulation study, we exercise data driven techniques and study efficiency of the event selection and the muon pT resolution as it can be done for the first data. The theory and experimental uncertainties are estimated ≲ 10% in the low-qT region and a few % for the high-qT region.;Also we present a first measurement of the multiplicity and transverse momentum flow in the first LHC collision data at 900 GeV center-of-mass energy recorded in December 2009. The systematic bias to the measurement due to the event selection and track reconstruction are estimated using the full CMS simulation. The results are compared to the predictions of one of the soft QCD models, previously studied by CDF collaboration at the Tevatron.