Charged particle multiplicities in pp interactions at sqrt(s) = 0.9, 2.36, and 7.0 TeV

We present a measurement of the charged particle multiplicity distributions for non-single-diffractive events in proton-proton collisions at $\sqrt{s} = 0.9$, 2.36, and 7\TeV, in various domains of pseudorapidity up to $| \eta | < 2.4$. The data were collected with the CMS detector during the LHC commissioning runs in 2009 and the 7\TeV run in 2010. The data are corrected for the trigger and event selection efficiency and the effects of tracking inefficiency and secondary tracks originating from the decay of long lived particles and products of interactions with the beam pipe and the detector material. The multiplicity distribution at $\sqrt{s} = 0.9$~\TeV is in agreement with previous experiments. At higher energies we observe a strong increase of the mean multiplicity with $\sqrt{s}$ which is underestimated by most Monte Carlo models. Our measurement of higher order moments of the multiplicity distribution confirms the violation of KNO scaling that was observed at lower energies. The measured multiplicity distributions and the average transverse momentum of charged primary particles as a function of the charged particle multiplicity, can serve as input to an improved Monte Carlo modeling of minimum bias events.