-- AminaZghiche - 2019-06-19

CMS-DP-2019/029

CMS ECAL Performance for Ultra Legacy re-reconstruction of 2017

Abstract: CMS ECAL , calibration and performance in 2017 ultra legacy re-reconstruction.

CDS entry

iCMS entry


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IC precision.png

2017 inter-calibration precision

Residual mis-calibration of the ECAL channel inter-calibration, as a function of pseudo-rapidity with the dataset recorded during 2017. The red, blue, and green points represent the residual mis-calibration of the inter-calibration constants (IC) obtained with three different methods, and the black points represent the residual mis-calibration of the combination of the three methods. The red points refer to the IC obtained with electrons from Z→ee decays using the known Z mass as energy reference. The blue points refer to IC obtained with electrons from W and Z decays using the tracker momentum as energy reference. The green points refer to IC obtained using photons from π0→γγ decays. Such decays are used only for abs(η)2.5, where only Z→ee decays are used.

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mee in EB fixedWidthNoFitLine.png

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mee in EE fixedWidthNoFitLine.png

Di-electron invariant mass distribution for the 2017 data taking period using Z→ee electrons.

The plot shows the di-electron invariant mass distribution for Z decay events with two calibration sets for the full 2017 dataset: the “preliminary” end-of-year 2017 calibration (RED) and a “refined” re-calibration performed in 2019 (GREEN). While for the refined calibration a complete re-calibration of the crystals was performed, for the preliminary calibration only time-dependent effects for the first part of the dataset were accounted for. Both electrons are required to be in the ECAL Barrel (left) or in the ECAL Endcaps (right). The relative resolutions are quoted in the legend, defined as the ratio of σ (Gaussian standard deviation of the Gaussian that is convoluted with a Breit-Wigner as the signal model (Voigtian fit)) to μ (mean).

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mee in EB LowR9 fixedWidthNoFitLine.png

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mee in EE LowR9 fixedWidthNoFitLine.png

Di-electron invariant mass distribution for the 2017 data taking period using Z→ee high-bremsstrahlung electrons.

The plot shows the di-electron invariant mass distribution for Z decay events with two calibration sets for the full 2017 dataset: the “preliminary” end-of-year 2017 calibration (RED) and a “refined” re-calibration performed in 2019 (GREEN). While for the refined calibration a complete re-calibration of the crystals was performed, for the preliminary calibration only time-dependent effects for the first part of the dataset were accounted for. Both electrons are required to be in the ECAL Barrel (left) or in the ECAL Endcaps (right) and to have high bremsstrahlung. The relative resolutions are quoted in the legend, defined as the ratio of σ (Gaussian standard deviation of the Gaussian that is convoluted with a Breit-Wigner as the signal model (Voigtian fit)) to μ (mean).

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mee in EB HighR9 fixedWidthNoFitLine.png

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mee in EE HighR9 fixedWidthNoFitLine.png

Di-electron invariant mass distribution for the 2017 data taking period using Z→ee low-bremsstrahlung electrons.

The plot shows the di-electron invariant mass distribution for Z decay events with two calibration sets for the full 2017 dataset: the “preliminary” end-of-year 2017 calibration (RED) and a “refined” re-calibration performed in 2019 (GREEN). While for the refined calibration a complete re-calibration of the crystals was performed, for the preliminary calibration only time-dependent effects for the first part of the dataset were accounted for. Both electrons are required to be in the ECAL Barrel (left) or in the ECAL Endcaps (right) and to have low bremsstrahlung. The relative resolutions are quoted in the legend, defined as the ratio of σ (Gaussian standard deviation of the Gaussian that is convoluted with a Breit-Wigner as the signal model (Voigtian fit)) to μ (mean).

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UL Resolution 2017 paper reso 1.png

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UL Resolution 2017 paper reso 2.png

ECAL energy resolution with Zee

Relative electron (ECAL) energy resolution unfolded in bins of pseudo-rapidity η for the ECAL Barrel and the ECAL Endcaps. Electrons from Z→ee decays are used. The resolution is shown separately for very low bremsstrahlung electrons (“golden”) and for all electrons (“inclusive”). The resolution is measured on 2017 data. The relative resolution σE/E is extracted from an unbinned likelihood fit to Z→ee events, using a Voigtian (Breit-Wigner convoluted with Gaussian) as the signal model.

Conclusions:

• The resolution is affected by the amount of material in front of the ECAL and is degraded in the vicinity of the eta cracks between ECAL modules (indicated by the vertical lines in the plot)

• The resolution improves significantly after a refined calibration using the full 2017 dataset with respect to a preliminary calibration for which only time dependent effects in the first part of the dataset were corrected for.

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pi0MassEBxtal index 30003.png

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pi0MassEExtal index 8155.png

Examples of the invariant mass of photon pairs with one photon depositing a fraction of its energy in a crystal of the ECAL Barrel at η = -0.03 (top), and of the ECAL Endcap at η = 1.82 (bottom), in the mass range of the π0. Data collected in 2017 and corresponding to an integrated luminosity of approximately 41.5 fb-1 are used. These events are collected by CMS with a dedicated trigger at a rate of 7 (2) kHz in the Barrel (Endcaps). The high trigger rate is made possible by a special clustering algorithm that saves only a minimal amount of information of the events, in particular energy deposits in the ECAL crystals surrounding a possible π0 candidate. For candidates in the Endcaps, the determination of the photon position in the region with 1.7 <η< 2.55 is improved by the presence of the Preshower, which results in a better mass resolution. These events are used as prompt feedback to monitor the effectiveness of the laser monitoring calibration and to inter-calibrate the energy of ECAL crystals. The π0 mass is obtained before the crystal inter-calibration.

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etaMassEBxtal index 30003.png

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etaMassEExtal index 8155.png

Examples of the invariant mass of photon pairs with one photon depositing a fraction of its energy in a crystal of the ECAL Barrel at η = -0.03 (top), and of the ECAL Endcapat η = 1.82 (bottom), in the mass range of the η0. Data collected in 2017 and corresponding to an integrated luminosity of approximately 41.5 fb-1 are used. These events are collected by CMS with a dedicated trigger at a rate of 3 (1) kHz in the Barrel (Endcaps). The high trigger rate is made possible by a special clustering algorithm that saves only a minimal amount of information of the events, in particular energy deposits in the ECAL crystals surrounding a possible η0 candidate. For candidates in the Endcaps, the determination of the photon position in the region with 1.7 <η< 2.55 is improved by the presence of the Preshower, which results in a better mass resolution. The lower trigger rate with respect to π0’s originates from the lower production cross section and branching ratio for decay into two photons (a global factor of about 10). This is partially compensated by the higher selection efficiency due to the larger resonance mass and consequently harder photon energy spectrum, which results in a better energy resolution compared to π0’s. Because of the smaller number of events, the precision of the ECAL inter-calibration with η0’s was lower than the one achieved with π0’s during Run2. However, given the higher energy of the photons, η0’s might provide competitive or better precision than π0’s during Run3 and the HL-LHC.

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medianR9eLvstimeinEB v2.png

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medianR9eLvstimeinEE v2.png

Stability of the shower shape of the electromagnetic deposits in the ECAL for leading electrons from Z decays.

The plot shows the time stability of the shower shape of the leading electron from Z decays with a refined re-calibration performed in 2019. The event selection requires two electrons to be in the ECAL Barrel (left) or in the ECAL Endcaps (right). Each time bin has around 10,000 events. The error bar on the points denotes the statistical uncertainty on the median, which is evaluated as the central 95% interval of medians obtained from 200 "bootstrap" re-samplings. The right panel shows the distribution of the medians. The shower shape is measured by the variable R9, defined as the ratio of the energy deposit in the 3x3 crystal matrix around the seed crystal to that in the supercluster. R9 is responsive to changes in pedestal and noise.

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medianmeeECALvstimeinEB v2.png

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medianmeeECALvstimeinEE v2.png

Time stability of the di-electron invariant mass distribution for the 2017 data taking period using Z→ee electrons.

The plot shows the time stability of the median di-electron invariant mass with a refined re-calibration performed in 2019 for the full 2017 dataset. Both electrons are required to be in the ECAL Barrel (left) or in the ECAL Endcaps (right). Each time bin has around 10,000 events. The error bar on the points denotes the statistical uncertainty on the median, which is evaluated as the central 95% interval of medians obtained from 200 "bootstrap" re-samplings.

The right panel shows the distribution of the medians.

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng IC_precision.png r1 manage 201.8 K 2019-06-21 - 14:36 ChiaraRovelli  
PDFpdf UL_Resolution_2017_paper_resoBrem.pdf r1 manage 37.6 K 2019-07-26 - 09:56 AminaZghiche  
PDFpdf UL_Resolution_2017_paper_resoGolden.pdf r1 manage 37.5 K 2019-07-26 - 09:56 AminaZghiche  
PDFpdf UL_Resolution_2017_paper_resoInclusive.pdf r1 manage 37.3 K 2019-07-26 - 09:56 AminaZghiche  
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PNGpng UL_Resolution_2017_paper_reso_2.png r1 manage 71.8 K 2019-07-05 - 17:27 AminaZghiche  
PDFpdf medianR9eLvstimeinEB.pdf r1 manage 68.0 K 2019-07-05 - 18:18 AminaZghiche  
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PNGpng medianR9eLvstimeinEB_v2.png r1 manage 58.2 K 2019-07-05 - 19:20 AminaZghiche  
PDFpdf medianR9eLvstimeinEE.pdf r1 manage 23.4 K 2019-07-05 - 18:58 AminaZghiche  
PNGpng medianR9eLvstimeinEE.png r1 manage 56.4 K 2019-07-05 - 18:22 AminaZghiche  
PDFpdf medianR9eLvstimeinEE_v2.pdf r1 manage 23.4 K 2019-07-05 - 19:23 AminaZghiche  
PNGpng medianR9eLvstimeinEE_v2.png r1 manage 56.4 K 2019-07-05 - 19:20 AminaZghiche  
PDFpdf medianmeeECALvstimeinEB.pdf r1 manage 69.1 K 2019-07-05 - 18:18 AminaZghiche  
PNGpng medianmeeECALvstimeinEB.png r1 manage 72.4 K 2019-07-05 - 18:22 AminaZghiche  
PDFpdf medianmeeECALvstimeinEB_v2.pdf r1 manage 69.1 K 2019-07-05 - 19:23 AminaZghiche  
PNGpng medianmeeECALvstimeinEB_v2.png r1 manage 72.4 K 2019-07-05 - 19:20 AminaZghiche  
PDFpdf medianmeeECALvstimeinEE.pdf r1 manage 24.2 K 2019-07-05 - 18:18 AminaZghiche  
PNGpng medianmeeECALvstimeinEE.png r1 manage 65.0 K 2019-07-05 - 18:22 AminaZghiche  
PDFpdf medianmeeECALvstimeinEE_v2.pdf r1 manage 24.2 K 2019-07-05 - 19:23 AminaZghiche  
PNGpng medianmeeECALvstimeinEE_v2.png r1 manage 65.0 K 2019-07-05 - 19:20 AminaZghiche  
PDFpdf mee_in_EB_HighR9_fixedWidthNoFitLine.pdf r1 manage 21.5 K 2019-07-05 - 18:51 AminaZghiche  
PNGpng mee_in_EB_HighR9_fixedWidthNoFitLine.png r1 manage 88.0 K 2019-07-05 - 18:51 AminaZghiche  
PDFpdf mee_in_EB_LowR9_fixedWidthNoFitLine.pdf r1 manage 21.5 K 2019-07-05 - 18:51 AminaZghiche  
PNGpng mee_in_EB_LowR9_fixedWidthNoFitLine.png r1 manage 88.5 K 2019-07-05 - 18:51 AminaZghiche  
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PNGpng mee_in_EE_HighR9_fixedWidthNoFitLine.png r1 manage 91.4 K 2019-07-05 - 18:51 AminaZghiche  
PDFpdf mee_in_EE_LowR9_fixedWidthNoFitLine.pdf r1 manage 21.5 K 2019-07-05 - 18:52 AminaZghiche  
PNGpng mee_in_EE_LowR9_fixedWidthNoFitLine.png r1 manage 91.9 K 2019-07-05 - 18:52 AminaZghiche  
PDFpdf mee_in_EE_fixedWidthNoFitLine.pdf r1 manage 21.5 K 2019-07-05 - 18:51 AminaZghiche  
PNGpng mee_in_EE_fixedWidthNoFitLine.png r1 manage 86.9 K 2019-07-05 - 18:51 AminaZghiche  

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Topic revision: r11 - 2019-10-02 - AminaZghiche
 
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