Measurement of Momentum Scale and Resolution of the CMS Detector using Low-mass Resonances and Cosmic Ray Muons

The momentum measurement of charged tracks is affected by systematic uncertainties due to the limited knowledge and modeling of the detector material, the magnetic field, the alignment and the reconstruction algorithms used to fit the track trajectory. In this paper it is shown that studying the mass of resonances, improvements in the modeling of the detector and in the track reconstruction can be achieved. A novel method to correct the track momentum measurement and to determine with precision its resolution is presented. Results at 7 TeV center-of-mass energy show deviations of order of per mille from the expectation, with an increase only at very low momentum ($p_T < 1$ GeV) and high pseudorapidity. For J/$\psi$ mesons a 0.2\% shift in the reconstructed dimuon mass is observed in addition to a slight parabolic dependence on the pseudorapidity. Both the shift and the pseudorapidity dependence are corrected within the statistical uncertainty. The resolution on muon transverse momentum is also measured and found to be within 5\% of the MC predictions. A method that uses cosmic ray muons to determine the momentum scale in the range of transverse momentum above 200 GeV, is also presented. With cosmic ray muons above 200 GeV a constant curvature offset is measured to be $\delta q/p_t = -0.044 \pm 0.022~\mathrm{TeV}^{-1}$.