A description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For tt events under typical 2011 pileup conditions, the average trackreconstruction efficiency for promptly-produced charged particles with transverse momenta of p T > 0.9 GeV is 94% for pseudorapidities of |η| < 0.9 and 85% for 0.9 < |η| < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of p T = 100 GeV emitted at |η| < 1.4, the resolutions are approximately 2.8% in p T , and respectively, 10 µm and 30 µm in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10-12 µm in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung.

The central component of the CMS detector is the largest silicon tracker ever built. The precise alignment of this complex device is a formidable challenge, and only achievable with a significant extension of the technologies routinely used for tracking detectors in the past. This article describes the full-scale alignment procedure as it is used during LHC operations. Among the specific features of the method are the simultaneous determination of up to 200 000 alignment parameters with tracks, the measurement of individual sensor curvature parameters, the control of systematic misalignment effects, and the implementation of the whole procedure in a multiprocessor environment for high execution speed. Overall, the achieved statistical accuracy on the module alignment is found to be significantly better than 10 µm.

The upgrade of the LHC to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a significantly higher radiation hardness. The CMS Tracker Collaboration has conducted an irradiation and measurement campaign to identify suitable silicon sensor materials and strip designs for the future outer tracker at the CMS experiment. Based on these results, the collaboration has chosen to use n-in-p type silicon sensors and focus further investigations on the optimization of that sensor type. This paper describes the main measurement results and conclusions that motivated this decision.

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The CMS pixel detector is the innermost tracking device at the LHC, reconstructing interaction vertices and charged particle trajectories. The current planar sensors located in the innermost layer of the pixel detector will be exposed to very high fluences which will degrade their performances. As a possible replacement for planar pixel sensors in the High Luminosity-LHC (HL-LHC), 3D silicon technology is under consideration due to its expected good performance in harsh radiation environments. Studies are also in progress for using 3D silicon pixel detectors in near-beam proton spectrometers at the LHC. Deep Reactive Ion Etching (DRIE) plays a key role in fabricating 3D silicon detectors in which readout and ohmic electrodes are processed through the silicon substrate instead of being implanted on the silicon surface. 3D pixel devices considered in this study were processed at FBK (Trento, Italy), bump bonded to the CMS pixel readout chip, and characterized in the laboratory. Numerical simulations were also carried out. We report on selected results from laboratory measurements and TCAD simulations.