Description and performance of track and primary-vertex reconstruction with the CMS tracker

By Cms Collaboration. 2014

885 citations recorded by the source corpus.

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 ttbar events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of pt>0.9 GeV is 94% for pseudorapidities of abs(eta)<0.9 and 85% for 0.9<abs(eta)<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 pt = 100 GeV emitted at abs(eta)<1.4, the resolutions are approximately 2.8% in pt, and respectively, 10 microns and 30 microns in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10-12 microns 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.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/935e5a3c440139e617d70b56473af05dcbc29486

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In Nuclear and High Energy Physics

Citations in the corpus

Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions (2015, background): “…angle, Ψ n , does vary for particles produced at different η regions, the following relation for r n ( η a , η b ) can be derived, In symmetric collision systems like PbPb, v n harmonics from symmetric positive ( v n ( η a ) ) and negative ( v n ( − η a ) ) η regions are identical after averaging…”
Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at √s = 8 TeV (2015, methodology): “5% for charged particles with pT = 100 GeV [4].”
Particle-flow reconstruction and global event description with the CMS detector (2017, methodology): “To increase the tracking efficiency while keeping the misreconstructed track rate at a similar level, the combinatorial track finder was applied in several successive iterations [18], each with moderate efficiency but with as high a purity as possible.”
Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV (2017, methodology): “While the position in the transverse plane is defined with a precision of 20 μm, its position along the beam line is not known [2].”
Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC (2020, background): “Any ambiguities that arise when a given tracker hit is assigned to multiple track candidates are resolved by dropping the track with fewer hits, or the track with the larger χ2 value if the number of hits is the same [10].”
Search for electroweak production of charginos and neutralinos in multilepton final states in proton-proton collisions at s=13$$ \sqrt{s}=13 $$ TeV (2017, background): “Light lepton candidates are required to be consistent with originating from the primary vertex, defined as the one with the largest p(2)T sum of the tracks pointing to that vertex [38].”
Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV (2016, background): “where wi is the weight assigned to the corresponding track by the adaptive vertex fit [27], based on its compatibility with the vertex.”