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Selection and processing of calibration samples to measure the particle identification performance of the LHCb experiment in Run 2

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Abstract

Since 2015, with the restart of the LHC for its second run of data taking, the LHCb experiment has been empowered with a dedicated computing model to select and analyse calibration samples to measure the performance of the particle identification (PID) detectors and algorithms. The novel technique was developed within the framework of the innovative trigger model of the LHCb experiment, which relies on online event reconstruction for most of the datasets, reserving offline reconstruction to special physics cases. The strategy to select and process the calibration samples, which includes a dedicated data-processing scheme combining online and offline reconstruction, is discussed. The use of the calibration samples to measure the detector PID performance, and the efficiency of PID requirements across a large range of decay channels, is described. Applications of the calibration samples in data-quality monitoring and validation procedures are also detailed.

Figures and captions

On the left, mass distributions of the decaying particles with the results of the fit superimposed; signal contributions are shown by the red dashed curves, and the total fit functions including background contributions are shown by the blue solid curves. On the right, the background-subtracted distributions of the calibration samples for electrons, muons, pions, kaons and protons as a function of the track pseudorapidity, $\eta$, and momentum $p$ are shown. The colour scale units are arbitrary.

c_Jpsi[..].pdf [121 KiB]
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c_JpsiEE0_c1.pdf
Coverage_E.pdf [173 KiB]
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Coverage_E.pdf
c_Jpsi_c1.pdf [154 KiB]
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c_Jpsi_c1.pdf
Covera[..].pdf [294 KiB]
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Coverage_Mu.pdf
c_KS0LL_c1.pdf [136 KiB]
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c_KS0LL_c1.pdf
Covera[..].pdf [298 KiB]
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Coverage_Pi.pdf
c_DstX_c1.pdf [132 KiB]
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c_DstX_c1.pdf
c_DstY_c1.pdf [132 KiB]
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c_DstY_c1.pdf
Coverage_K.pdf [305 KiB]
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Coverage_K.pdf
c_Lam0[..].pdf [133 KiB]
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c_Lam0LL_c1.pdf
Coverage_P.pdf [254 KiB]
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Coverage_P.pdf

Schematic representation of the PID resampling and variable transformation techniques.

PIDGen.pdf [26 KiB]
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PIDGen.pdf

Schematic representation of the computing model for the PID calibration samples.

comput[..].pdf [51 KiB]
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computingModel.pdf

Animated gif made out of all figures.

DP-2018-001.gif
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thumbnail_DP-2018-001.gif

Tables and captions

Input variables of the ANNPID classifiers for the various subsystems of the LHCb detector.

Table_1.pdf [44 KiB]
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tex code
Table_1.pdf

Overview of decay modes that are used to select calibration samples. The high momentum samples are primarily selected, while the low momentum samples are included to maximise the kinematic coverage as much as possible.”

Table_2.pdf [68 KiB]
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tex code
Table_2.pdf

Created on 21 September 2019.