# CMS Tracker Performance results for full Run 2 Legacy reprocessing

Contact: The CMS Tracker DPG conveners (cms-dpg-conveners-tracker@cernNOSPAMPLEASE.ch)
and the CMS Tracker Performance hypernews (hn-cms-trackerperformance@cernNOSPAMPLEASE.ch).
Public CDS Records: CMS-DP-2020-012, [[][CMS-DP-2020-0XX]]

%COMPLETE5%

Tracker alignment validation was performed by means of the following methods:

• Primary Vertices Validation [1]
• DMR and DRmsNR Validation [2]
• Muon Track-Split Validation [3]
• Validation [2]

## Overlap Validation

 Overlap Validation Diagrams [PNG format] Description Diagram demonstrating shift in coordinate of predicted hits for modules overlapping in the direction of the tracker. An overlap in any direction is defined as any track with hits in two consecutive modules in the same layer of the detector. In this diagram, module A and module B are in the same layer of the tracker and have hits from the same track. Modules only differ in their coordinate so we say these modules are overlapping in the phi direction. We show effects under both radial expansion and contraction. Also note that shift of the effective charge collection location on the module can also cause of shifts in measured hit location Figure: Diagram demonstrating effect of radial expansion on measured coordinate for modules overlapping in the direction of the tracker. Definition of measured difference in measured hit and predicted hit is given as well. This quantity would be defined as or the difference in residuals for modules overlapping in the direction in the tracker.

 Overlap Validation Trends [PNG format] Description The mean difference in z residuals for modules overlapping in the z direction in the Barrel Pixel (), as a function of processed luminosity. The non-zero value of the mean difference of residuals could be explained either by the geometrical shift of the modules, such as expansion of the detector along the z axis, or by the shift of the effective charge collection location, such as imperfect recovering of the Lorentz angle effects. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. There is an improvement of End-of-year and Legacy Reprocessing over Alignment during data taking. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3]. The mean difference in residuals for modules overlapping in the direction in the Barrel Pixel (), as a function of processed luminosity. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The non-zero value of the mean difference of residuals could be explained either by the geometrical shift of the modules, such as expansion of the detector along the r axis, or by the shift of the effective charge collection location. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. There is an improvement of End-of-year and Legacy Reprocessing over Alignment during data taking. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3]. The mean difference in residuals for modules overlapping in the z direction in the Barrel Pixel () , as a function of processed luminosity. The non-zero value of the mean difference of residuals could be explained either by the geometrical shift of the modules or by the shift of the effective charge collection location. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. There is an improvement of End-of-year and Legacy Reprocessing over Alignment during data taking. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3]. The mean difference in z residuals for modules overlapping in the direction in the Barrel Pixel ) , as a function of processed luminosity. The non-zero value of the mean difference of residuals could be explained either by the geometrical shift of the modules or by the shift of the effective charge collection location. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. There is an improvement of End-of-year and Legacy Reprocessing over Alignment during data taking. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3].

 Overlap Validation Plots [PNG format] Distribution of difference in z residuals for modules overlapping in the z direction for the Barrel Pixel of the tracker (). As a representative example, run from 04 July 2016 was selected. The blue line corresponds to the results with the alignment constants used during data-taking, the red lines show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction, the green lines show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. The quoted means and standard deviations are the parameters of a Gaussian fit to the distributions. Distribution of difference in residuals for modules overlapping in the direction for the Barrel Pixel of the tracker (). As a representative example, run from 04 July 2016 was selected. The blue line corresponds to the results with the alignment constants used during data-taking, the red lines show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction, the green lines show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. The quoted means $\mu$ and standard deviations are the parameters of a Gaussian fit to the distributions. Distribution of difference in residuals for modules overlapping in the z direction for the Barrel Pixel of the tracker (). As an example, run from 04 July 2016 was selected. The blue line corresponds to the results with the alignment constants used during data-taking, the red lines show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction, the green lines shows the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. The quoted means $\mu$ and standard deviations are the parameters of a Gaussian fit to the distributions. Distribution of difference in z residuals for modules overlapping in the direction for the Barrel Pixel of the tracker (). As an example, run from 04 July 2016 was selected. The blue line corresponds to the results with the alignment constants used during data-taking, the red lines show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction, the lines show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure.The quoted means $\mu$ and standard deviations are the parameters of a Gaussian fit to the distributions.

Geometry Comparison:

• Compare the positions of each module to a reference alignment
• Trends in positions of modules are indicative of global deformation in tracker geometry
• Large trends do not imply bad alignment. If deformations are shown in Geometry comparison, it means that they were accounted for in alignment.

 Geometry Comparison Trends [PNG format] The slope () given by fitting the difference in the measured z position vs z for each module in the Barrel Pixel with respect to a reference alignment constraint, to a linear function of the form as a function of processed luminosity. A non-zero indicates a z-expansion of the geometry relative to the reference geometry. = 0.1 corresponds to a z-expansion/contraction of 2.6 at z = 26cm. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue points correspond to the results with the alignment constants used during data-taking, the red points show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green points show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3]. In 2016,2017 and 2018 we compare to the Legacy Reprocessing geometry for pp collisions on 8 August 2016, 10 July 2017, and 8 August 2018 respectively. The slope () given by fitting the difference in the measured z position vs z for each module in the Barrel Pixel with respect to a reference alignment constraint, to a linear function of the form as a function of processed luminosity. The shift between 2017 and 2018 can be caused by some global shift of the large scale structure of the Barrel Pixel along the z axis. = 0.1 corresponds to a z-expansion/contraction of 2.6 at z = 26cm relative to the reference alignment. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue points correspond to the results with the alignment constants used during data-taking, the red points show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green points show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3]. In 2016,2017 and 2018 we compare to the Legacy Reprocessing geometry for pp collisions on 8 August 2016, 10 July 2017, and August 8 2018 respectively. The slope given by fitting the difference in the measured r position )vs r for each module in the Barrel Pixel with respect to a reference alignment constraint, to a linear function of the form as a function of processed luminosity. A non-zero indicates a radial expansion of the geometry relative to the reference geometry. = 0.2 corresponds to a radial expansion/contraction of 3.2 at r = 16 . The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the inner component (pixel detector) of the CMS tracking detector was replaced [3]. In 2016,2017 and 2018 we compare to the Legacy Reprocessing geometry for pp collisions on 8 August 2016, 10 July 2017, and August 8 2018 respectively. The slope () given by fitting the difference in the measured r position () vs r for each module in the Barrel Pixel with respect to a reference alignment constraint, to a linear function of the form as a function of processed luminosity. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The shift between 2017 and 2018 can be caused by some global shift of the two shells of the Barrel Pixel such as expansion or contraction along the x axis. = 0.2 corresponds to a radial expansion/contraction of 3.2 at r = 16 . The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the inner component (pixel detector) of the CMS tracking detector was replaced [3]. In 2016 we compare to the Legacy Reprocessing geometry for pp collisions on 8 August 2016 and in 2017 and 2018 we compare to the Legacy Reprocessing geometry for pp collisions on 05 April 2018. The slope () given by fitting the difference in the measured r position () vs z for each module in the Barrel Pixel with respect to a reference alignment constraint, to a linear function of the form as a function of processed luminosity. A non-zero indicates a twist of the geometry relative to the reference geometry. = 0.01 corresponds to a twist of 2.6 (Constant at all r). The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue points correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green points show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3]. In 2016,2017 and 2018 we compare to the Legacy Reprocessing geometry for pp collisions on 8 August 2016, 10 July 2017, and 8 August 2018 respectively. The slope () given by fitting the difference in the measured r position () vs z for each module in the Barrel Pixel with respect to a reference alignment constraint, to a linear function of the form as a function of processed luminosity. The shift between 2017 and 2018 can be caused by some global shift of the shells of the Barrel Pixel such as a non zero angle of a shell with respect to the z axis in the y-z plane. = 0.01 corresponds to a twist of 5$\mp$% 2.6 5$mrad$% (Constant at all r) The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue points correspond to the results with the alignment constants used during data-taking, the red points show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green points show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3]. In 2016 we compare to the Legacy Reprocessing geometry for pp collisions on 8 August 2016 and in 2017 and 2018 we compare to the Legacy Reprocessing geometry for pp collisions on 05 April 2018.

Validation:

• In an ideal detector we expect to see no dependence dependence of Z mass on spatial variables of the tracks.

 Trends [PNG format] The Amplitude (A) given by fitting Z Mass vs the azimuth angle() of the positive track to a function of the form as a function of processed luminosity. This Amplitude shows the average spread of the Z-mass with respects to ,which is expected to be zero in a well aligned detector. A non-zero Amplitude indicates that reconstructed mass has some dependence on the spatial coordinates of the detector. We observe significant improvement between Legacy Reprocessing and other alignment campaigns. Error bars correspond to the uncertainty on fitting parameters calculated by regression.The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3]. The RMS of Z masses binned over as a function of processed luminosity. The RMS a good measure of the spread of the Z-mass with respects to ,which is expected to be zero in a well aligned detector. A non-zero RMS indicates that reconstructed mass has some dependence on the spatial coordinates of the detector. We observe significant improvement between Legacy Reprocessing and other alignment campaigns. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3] The slope () given by fitting Z Mass vs of the two Muons to a linear function of the form as a function of processed luminosity. In an ideal alignment we expect that reconstructed mass has no dependence on the pseudo-rapidities of decay products between -2 and 2. At these pseudo-rapidities, particles travel through most of the active area of the Barrel Pixel. We observe significant improvement between Legacy Reprocessing and other alignment campaigns. The vertical black solid lines indicate the first processed run for 2016, 2017 and 2018 data-taking period, respectively. The vertical dotted lines indicate a change in the pixel tracker calibration. The blue bands correspond to the results with the alignment constants used during data-taking, the red bands show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction (notice there is no EOY re-reconstruction for the last 33 of data-taking), the green bands show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. During the LHC shutdown in winter 2016/17, the pixel detector was replaced [3].

 Validation [PNG format] Plot of Z mass vs . As a representative example, run from 14 August 2018 was selected. The blue points correspond to the results with the alignment constants used during data-taking, the red points show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction, the green points show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. The fitted lines are obtained by fitting Z mass vs to function of the form . Fit is only considered from -2 to 2 due to nonlinear behavior outside of this range. Plot of Z mass vs the azimuth angle() of the positive . As a representative example, run from 01 September 2016 was selected. The blue points corresponds to the results with the alignment constants used during data-taking, the red points show the results with the alignment constants used during the 2016, 2017 and 2018 End-Of-Year (EOY) re-reconstruction, the green points show the results with the alignment constants as obtained in the Run-2 Legacy alignment procedure. The fitted lines are obtained by fitting Z Mass vs the azimuth angle () to a function of the form . Any systematic distortion over some periodic boundary is expected to also be periodic, which motivates our fit. This can be interpreted as the first Fourier mode of the function that parameterizes our distortion.
-- JeffreyDavis - 2020-04-09
Topic attachments
I Attachment History Action Size Date Who Comment
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