Abstract
The expected performance of track reconstruction with LHC events using the CMS silicon tracker is presented. Track finding and fitting is accomplished with Kalman Filter techniques that achieve efficiencies above 99% on single muons with pT>1 GeV/c. Difficulties arise in the context of standard LHC events with a high density of charged particles, where the rate of fake combinatorial tracks is very large for low pT tracks, and nuclear interactions in the tracker material reduce the tracking efficiency for charged hadrons. Recent improvements with the CMS track reconstruction now allow to efficiently reconstruct charged tracks with pT down to few hundred MeV/c and as few as three crossed layers, with a very small fake fraction, by making use of an optimal rejection of fake tracks in conjunction with an iterative tracking procedure.
Highlights
Tracking at the LHC is an experimental challenge
In CMS track reconstruction relies on a silicon pixel and micro-strip tracker immersed in a 3.8 T solenoidal magnetic field along the beam line
In the seeding stage pairs of hits, that are compatible with the interaction region above a lower pT limit, are considered as possible candidates of charged tracks
Summary
Tracking at the LHC is an experimental challenge. At the design luminosity √of 1034 cm−2s−1 the proton-proton collisions at s=14 TeV will produce on average 20 superimposed events at a bunch crossing rate of 40 MHz. Each bunch crossing will produce on average about 2000 charged tracks in the |η| < 2.5 range, resulting in a density of 2.5 charged tracks per cm at η = 0, at a distance of 4 cm from the interaction region. In CMS track reconstruction relies on a silicon pixel and micro-strip tracker immersed in a 3.8 T solenoidal magnetic field along the beam line. The CMS reference system has origin at the detector and interaction region center, with the z-axis along the beam line, the y-axis upwards and the x-axis in the direction of the LHC center. The transverse plane is denoted as the xy or rφ plane
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