First physics with hadrons and the underlying event at CMS

The early data from LHC will allow the first look at minimum bias p-p collisions initially at the center-of-mass energies of 10 and later 14 TeV. The measurements of the basic observables will also serve as an important tool for calibrating and understanding the CMS detector at start-up. \medskip We present the plans of the CMS collaboration to measure cross sections and differential yields of charged particles (unidentified or identified pions, kaons and protons) and neutrals ($\mathrm{K_S^0}$, lambdas and anti-lambdas) produced in inelastic p-p collisions at 14 TeV, as well as their multiplicity distributions. The tracking of charged particles is possible down to about 100 MeV/c, with good efficiency and negligible fake rate. The yield of charged kaons and protons can be extracted for total momenta below 0.8 and 1.5 GeV/c, respectively. Comparisons of the results to theoretical models are discussed. Studies of the underlying event at CMS are presented by examining charged particle and momentum densities in the transverse region in charged particle jet production. The possibility of discriminating among models is shown.