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Measurement of the track reconstruction efficiency at LHCb

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Abstract

The determination of track reconstruction efficiencies at LHCb using $J/\psi\rightarrow\mu^{+}\mu^{-}$ decays is presented. Efficiencies above $95\%$ are found for the data taking periods in 2010, 2011, and 2012. The ratio of the track reconstruction efficiency of muons in data and simulation is compatible with unity and measured with an uncertainty of $0.8 \%$ for data taking in 2010, and at a precision of $0.4 \%$ for data taking in 2011 and 2012. For hadrons an additional $1.4 \%$ uncertainty due to material interactions is assumed. This result is crucial for accurate cross section and branching fraction measurements in LHCb.

Figures and captions

Tracking detectors and track types reconstructed by the track finding algorithms at LHCb.

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lhcb.pdf

Illustration of the three tag-and-probe methods: (a) the VELO method, (b) the T-station method, and (c) the long method. The VELO (black rectangle), the two TT layers (short bold lines), the magnet coil, the three T stations (long bold lines), and the five muon stations (thin lines) are shown in all three subfigures. The upper solid blue line indicates the tag track, the lower line indicates the probe with red dots where hits are required and dashes where a detector is probed.

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trackEffIllustrationDownstream.pdf
trackE[..].pdf [2 KiB]
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trackEffIllustrationVeloMuon.pdf
trackE[..].pdf [2 KiB]
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trackEffIllustrationMuonTT.pdf

Invariant mass distributions for reconstructed $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ candidates from the 2011 dataset. The solid line shows the fitted distribution for signal and background, the dotted line is the signal component. The subfigures are (a) the VELO method, (b) the T-station method, (c) the long method. For comparison of resolution and signal purity (d) shows the invariant mass distribution of $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ candidates obtained with the standard reconstruction at LHCb.

Velo_m[..].pdf [25 KiB]
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Velo_massFit2011.pdf
Tstati[..].pdf [23 KiB]
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Tstation_massFit2011.pdf
Long_m[..].pdf [46 KiB]
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Long_massFit2011.pdf
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Standard_massFit.pdf

Track reconstruction efficiencies for the 2010 data and for weighted simulation. The left-hand column shows the results of the combined method while the right-hand column shows the results of the long method. The efficiency is shown as a function of $p$ (first row), $\eta$ (second row), $N_{\rm track}$ (third row), and $N_{\rm PV}$ (fourth row). The error bars indicate the statistical uncertainties.

combin[..].pdf [14 KiB]
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combined_effVsP2010.pdf
Long_e[..].pdf [14 KiB]
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Long_effVsP2010.pdf
combin[..].pdf [14 KiB]
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combined_effVsEta2010.pdf
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Long_effVsEta2010.pdf
combin[..].pdf [14 KiB]
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combined_effVstrackmult2010.pdf
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Long_effVstrackmult2010.pdf
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combined_effVsnpv2010.pdf
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Long_effVsnpv2010.pdf

Track reconstruction efficiencies for the 2011 data and for weighted simulation. The left-hand column shows the results of the combined method while the right-hand column shows the results of the long method. The efficiency is shown as a function of $p$ (first row), $\eta$ (second row), $N_{\rm track}$ (third row), and $N_{\rm PV}$ (fourth row). The error bars indicate the statistical uncertainties.

combin[..].pdf [14 KiB]
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combined_effVsP2011S20MC17.pdf
Long_e[..].pdf [14 KiB]
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Long_effVsP2011S20MC17.pdf
combin[..].pdf [13 KiB]
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combined_effVsEta2011S20MC17.pdf
Long_e[..].pdf [14 KiB]
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Long_effVsEta2011S20MC17.pdf
combin[..].pdf [14 KiB]
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combined_effVstrackmult2011S20MC17.pdf
Long_e[..].pdf [14 KiB]
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Long_effVstrackmult2011S20MC17.pdf
combin[..].pdf [14 KiB]
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combined_effVsnpv2011S20MC17.pdf
Long_e[..].pdf [14 KiB]
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Long_effVsnpv2011S20MC17.pdf

Track reconstruction efficiencies for the 2012 data and for weighted simulation. The left-hand column shows the results of the combined method while the right-hand column shows the results of the long method. The efficiency is shown as a function of $p$ (first row), $\eta$ (second row), $N_{\rm track}$ (third row), and $N_{\rm PV}$ (fourth row). The error bars indicate the statistical uncertainties.

combin[..].pdf [14 KiB]
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combined_effVsP2012S20.pdf
Long_e[..].pdf [14 KiB]
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Long_effVsP2012S20.pdf
combin[..].pdf [13 KiB]
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combined_effVsEta2012S20.pdf
Long_e[..].pdf [14 KiB]
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Long_effVsEta2012S20.pdf
combin[..].pdf [14 KiB]
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combined_effVstrackmult2012S20.pdf
Long_e[..].pdf [14 KiB]
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Long_effVstrackmult2012S20.pdf
combin[..].pdf [14 KiB]
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combined_effVsnpv2012S20.pdf
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Long_effVsnpv2012S20.pdf

Track reconstruction efficiency ratios as a function of $p$ between data and simulation for (left) 2010 data, (right) 2011 data, and (bottom) 2012 data.

ratioP[..].pdf [14 KiB]
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ratioPlot2010.pdf
ratioP[..].pdf [14 KiB]
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ratioPlot2011S20MC17.pdf
ratioP[..].pdf [14 KiB]
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ratioPlot2012S20.pdf

Animated gif made out of all figures.

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Tables and captions

Settings of the software trigger selection as a function of data taking period. Only the tag muon is required to pass the selection. For more information see Refs. [26,27,28,9].

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Table_1.pdf

Selection requirements on the tag and probe tracks and on the combination into a $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} $ candidate for the three different methods.

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Table_2.pdf

Track reconstruction efficiencies in % for the individual running periods using the long method for positive and negative muons and different magnetic field polarities (statistical uncertainties only).

Table_3.pdf [49 KiB]
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Table_3.pdf

Created on 12 October 2019.