The European Physical Journal C > 2017 > 77 > 10 > 1-30
Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2
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Abstract
With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 $$\text {TeV}$$ TeV for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb$$^{-1}$$ -1 of data collected by the ATLAS experiment and simulation of proton–proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 $$\text {TeV}$$ TeV . The impact of charged-particle separations and multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 $$\text {GeV}$$ GeV is quantified using a novel, data-driven, method. The method uses the energy loss, $${\text { d}}{} \textit{E}/d\textit{x}$$ dE/dx , to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is $$0.061 \pm 0.006\ {\text {(stat.)}} \pm 0.014\ {\text {(syst.)}}$$ 0.061±0.006(stat.)±0.014(syst.) and $$0.093 \pm 0.017\ {\text {(stat.)}}\pm 0.021\ {\text {(syst.)}}$$ 0.093±0.017(stat.)±0.021(syst.) for jet transverse momenta of 200–400 $$\text {GeV}$$ GeV and 1400–1600 $$\text {GeV}$$ GeV , respectively.
Identifiers
journal ISSN : | 1434-6044 |
journal e-ISSN : | 1434-6052 |
DOI | 10.1140/epjc/s10052-017-5225-7 |