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CMS-PAS-SMP-18-012
Measurement of the W boson rapidity, helicity, and differential cross sections in pp collisions at $\sqrt{s}= $ 13 TeV
Abstract: The differential cross section and charge asymmetry for inclusive W boson production at $\sqrt{s}= $ 13 TeV is measured for the two transverse polarization states as a function of the W boson absolute rapidity. The measurement uses events in which a W boson decays to either an electron or a muon and a neutrino. The data sample of proton-proton collisions recorded with the CMS detector at the LHC in 2016 corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The absolute differential cross section, and its value normalized to the total inclusive W boson production cross section, are measured over the rapidity range $| Y_{\mathrm{W}} | < $ 2.5. In addition, the W boson double-differential cross section, $\mathrm{d}^2\sigma/\mathrm{d}p_{\mathrm{T}}^{\ell} \mathrm{d}|\eta^{\ell}|$, and the charge asymmetry, are measured as a function of the charged lepton transverse momentum and pseudorapidity. The precision of these measurements is used to constrain the parton density functions (PDF) of the proton using the next-to-leading-order PDF set NNPDF3.0.
Figures & Tables Summary Additional Figures References CMS Publications
Figures

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Figure 1:
Distributions of the W boson ${p_{\mathrm {T}} ^{\mathrm{W}}}$ (left), ${| Y_{\mathrm{W}} |}$ (center), and the resulting $\eta $ distribution of the charged lepton (right) after reweighting each of the helicity components for positive (top row) and negative charge (bottom row) W bosons.

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Figure 1-a:
Distributions of the W boson ${p_{\mathrm {T}} ^{\mathrm{W}}}$ (left), ${| Y_{\mathrm{W}} |}$ (center), and the resulting $\eta $ distribution of the charged lepton (right) after reweighting each of the helicity components for positive (top row) and negative charge (bottom row) W bosons.

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Figure 1-b:
Distributions of the W boson ${p_{\mathrm {T}} ^{\mathrm{W}}}$ (left), ${| Y_{\mathrm{W}} |}$ (center), and the resulting $\eta $ distribution of the charged lepton (right) after reweighting each of the helicity components for positive (top row) and negative charge (bottom row) W bosons.

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Figure 1-c:
Distributions of the W boson ${p_{\mathrm {T}} ^{\mathrm{W}}}$ (left), ${| Y_{\mathrm{W}} |}$ (center), and the resulting $\eta $ distribution of the charged lepton (right) after reweighting each of the helicity components for positive (top row) and negative charge (bottom row) W bosons.

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Figure 1-d:
Distributions of the W boson ${p_{\mathrm {T}} ^{\mathrm{W}}}$ (left), ${| Y_{\mathrm{W}} |}$ (center), and the resulting $\eta $ distribution of the charged lepton (right) after reweighting each of the helicity components for positive (top row) and negative charge (bottom row) W bosons.

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Figure 1-e:
Distributions of the W boson ${p_{\mathrm {T}} ^{\mathrm{W}}}$ (left), ${| Y_{\mathrm{W}} |}$ (center), and the resulting $\eta $ distribution of the charged lepton (right) after reweighting each of the helicity components for positive (top row) and negative charge (bottom row) W bosons.

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Figure 1-f:
Distributions of the W boson ${p_{\mathrm {T}} ^{\mathrm{W}}}$ (left), ${| Y_{\mathrm{W}} |}$ (center), and the resulting $\eta $ distribution of the charged lepton (right) after reweighting each of the helicity components for positive (top row) and negative charge (bottom row) W bosons.

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Figure 2:
Distributions of 2D templates of ${{p_{\mathrm {T}}} ^{\ell}}$ versus ${\eta ^{\ell}}$, for positively charged W boson simulated events with different helicity or rapidity bin. Blue: $ {\mathrm{W^{+}} _{R}} $ with $ {| Y_{\mathrm{W}} |} < $ 0.25, red: $ {\mathrm{W^{+}} _{R}} $ with 0.5 $ < {| Y_{\mathrm{W}} |} < $ 0.75, green: $ {\mathrm{W^{+}} _{L}} $ with 2.0 $ < {| Y_{\mathrm{W}} |} < $ 2.25.

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Figure 3:
Top: relative impact of groups of uncertainties (as defined in the text) on the signal normalized cross sections for the $ {\mathrm{W^{-}} _{L}} $ case. Bottom: absolute impact of uncertainties on the charge asymmetry of $ {\mathrm{W} _{L}} $. All impacts are shown for the combination of the muon and electron channels.

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Figure 3-a:
Top: relative impact of groups of uncertainties (as defined in the text) on the signal normalized cross sections for the $ {\mathrm{W^{-}} _{L}} $ case. Bottom: absolute impact of uncertainties on the charge asymmetry of $ {\mathrm{W} _{L}} $. All impacts are shown for the combination of the muon and electron channels.

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Figure 3-b:
Top: relative impact of groups of uncertainties (as defined in the text) on the signal normalized cross sections for the $ {\mathrm{W^{-}} _{L}} $ case. Bottom: absolute impact of uncertainties on the charge asymmetry of $ {\mathrm{W} _{L}} $. All impacts are shown for the combination of the muon and electron channels.

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Figure 4:
Top: relative impact of groups of systematic uncertainties (as defined in the text) on the signal normalized cross sections for the $ {\mathrm{W^{+}}} $ case. Bottom: relative impact of uncertainties on charge asymmetry (bottom). All impacts are shown for the combination of the muon and electron channels.

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Figure 4-a:
Top: relative impact of groups of systematic uncertainties (as defined in the text) on the signal normalized cross sections for the $ {\mathrm{W^{+}}} $ case. Bottom: relative impact of uncertainties on charge asymmetry (bottom). All impacts are shown for the combination of the muon and electron channels.

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Figure 4-b:
Top: relative impact of groups of systematic uncertainties (as defined in the text) on the signal normalized cross sections for the $ {\mathrm{W^{+}}} $ case. Bottom: relative impact of uncertainties on charge asymmetry (bottom). All impacts are shown for the combination of the muon and electron channels.

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Figure 5:
Distributions of ${\eta ^{\, \mu}}$ (a), ${{p_{\mathrm {T}}} ^{\, \mu}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{+}}} \to \mu ^+\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 5-a:
Distributions of ${\eta ^{\, \mu}}$ (a), ${{p_{\mathrm {T}}} ^{\, \mu}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{+}}} \to \mu ^+\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 5-b:
Distributions of ${\eta ^{\, \mu}}$ (a), ${{p_{\mathrm {T}}} ^{\, \mu}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{+}}} \to \mu ^+\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 5-c:
Distributions of ${\eta ^{\, \mu}}$ (a), ${{p_{\mathrm {T}}} ^{\, \mu}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{+}}} \to \mu ^+\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 6:
Distributions of ${\eta ^{\, \mu}}$ (a), ${{p_{\mathrm {T}}} ^{\, \mu}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{-}}} \to \mu ^-\bar\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 6-a:
Distributions of ${\eta ^{\, \mu}}$ (a), ${{p_{\mathrm {T}}} ^{\, \mu}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{-}}} \to \mu ^-\bar\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 6-b:
Distributions of ${\eta ^{\, \mu}}$ (a), ${{p_{\mathrm {T}}} ^{\, \mu}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{-}}} \to \mu ^-\bar\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 6-c:
Distributions of ${\eta ^{\, \mu}}$ (a), ${{p_{\mathrm {T}}} ^{\, \mu}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{-}}} \to \mu ^-\bar\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 7:
Distributions of ${\eta ^{\mathrm{e}}}$ (a), ${{p_{\mathrm {T}}} ^{\mathrm{e}}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{+}}} \to \mathrm{e} ^+\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 7-a:
Distributions of ${\eta ^{\mathrm{e}}}$ (a), ${{p_{\mathrm {T}}} ^{\mathrm{e}}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{+}}} \to \mathrm{e} ^+\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 7-b:
Distributions of ${\eta ^{\mathrm{e}}}$ (a), ${{p_{\mathrm {T}}} ^{\mathrm{e}}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{+}}} \to \mathrm{e} ^+\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 7-c:
Distributions of ${\eta ^{\mathrm{e}}}$ (a), ${{p_{\mathrm {T}}} ^{\mathrm{e}}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{+}}} \to \mathrm{e} ^+\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 8:
Distributions of ${\eta ^{\mathrm{e}}}$ (a), ${{p_{\mathrm {T}}} ^{\mathrm{e}}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{-}}} \to \mathrm{e} ^-\bar\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 8-a:
Distributions of ${\eta ^{\mathrm{e}}}$ (a), ${{p_{\mathrm {T}}} ^{\mathrm{e}}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{-}}} \to \mathrm{e} ^-\bar\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 8-b:
Distributions of ${\eta ^{\mathrm{e}}}$ (a), ${{p_{\mathrm {T}}} ^{\mathrm{e}}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{-}}} \to \mathrm{e} ^-\bar\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 8-c:
Distributions of ${\eta ^{\mathrm{e}}}$ (a), ${{p_{\mathrm {T}}} ^{\mathrm{e}}}$ (b) and bin$_{{\text{unrolled}}}$ (c) for $ {\mathrm{W^{-}}} \to \mathrm{e} ^-\bar\nu $ events for observed data superimposed on signal plus background events. The signal and background processes are normalized to the result of the template fit. The cyan band over the data-to-prediction ratio represents the uncertainty in the yield in each bin after the profiling process.

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Figure 9:
Measured normalized $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (middle) cross section as a function of $ {| Y_{\mathrm{W}} |} $ for the left-handed and right-handed helicity states from the combination of muon and electron channels, normalized to the total cross section. Right: measured W charge asymmetry. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 9-a:
Measured normalized $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (middle) cross section as a function of $ {| Y_{\mathrm{W}} |} $ for the left-handed and right-handed helicity states from the combination of muon and electron channels, normalized to the total cross section. Right: measured W charge asymmetry. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 9-b:
Measured normalized $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (middle) cross section as a function of $ {| Y_{\mathrm{W}} |} $ for the left-handed and right-handed helicity states from the combination of muon and electron channels, normalized to the total cross section. Right: measured W charge asymmetry. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 9-c:
Measured normalized $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (middle) cross section as a function of $ {| Y_{\mathrm{W}} |} $ for the left-handed and right-handed helicity states from the combination of muon and electron channels, normalized to the total cross section. Right: measured W charge asymmetry. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 10:
Measured normalized $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (middle) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from the combination of muon and electron channels, normalized to the total cross section, integrated over the W polarization states. Right: measured W charge asymmetry. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 10-a:
Measured normalized $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (middle) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from the combination of muon and electron channels, normalized to the total cross section, integrated over the W polarization states. Right: measured W charge asymmetry. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 10-b:
Measured normalized $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (middle) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from the combination of muon and electron channels, normalized to the total cross section, integrated over the W polarization states. Right: measured W charge asymmetry. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 10-c:
Measured normalized $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (middle) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from the combination of muon and electron channels, normalized to the total cross section, integrated over the W polarization states. Right: measured W charge asymmetry. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 11:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from the combined flavor fit. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 11-a:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from the combined flavor fit. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 11-b:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from the combined flavor fit. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 12:
Normalized double-differential cross section and charge asymmetry as a function of the ${{p_{\mathrm {T}}} ^{\ell}}$ and ${| \eta ^{\ell}|}$, unrolled in a 1D histogram along ${| \eta ^{\ell}|}$ for the positive (negative) charge on top (middle). The bottom plot shows the resulting charge asymmetry. The lower panel in each plot shows the ratio (difference) of the observed and expected cross section (asymmetry).

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Figure 12-a:
Normalized double-differential cross section and charge asymmetry as a function of the ${{p_{\mathrm {T}}} ^{\ell}}$ and ${| \eta ^{\ell}|}$, unrolled in a 1D histogram along ${| \eta ^{\ell}|}$ for the positive (negative) charge on top (middle). The bottom plot shows the resulting charge asymmetry. The lower panel in each plot shows the ratio (difference) of the observed and expected cross section (asymmetry).

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Figure 12-b:
Normalized double-differential cross section and charge asymmetry as a function of the ${{p_{\mathrm {T}}} ^{\ell}}$ and ${| \eta ^{\ell}|}$, unrolled in a 1D histogram along ${| \eta ^{\ell}|}$ for the positive (negative) charge on top (middle). The bottom plot shows the resulting charge asymmetry. The lower panel in each plot shows the ratio (difference) of the observed and expected cross section (asymmetry).

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Figure 12-c:
Normalized double-differential cross section and charge asymmetry as a function of the ${{p_{\mathrm {T}}} ^{\ell}}$ and ${| \eta ^{\ell}|}$, unrolled in a 1D histogram along ${| \eta ^{\ell}|}$ for the positive (negative) charge on top (middle). The bottom plot shows the resulting charge asymmetry. The lower panel in each plot shows the ratio (difference) of the observed and expected cross section (asymmetry).

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Figure 13:
Absolute double-differential cross section as a function of ${{p_{\mathrm {T}}} ^{\ell}}$ and ${| \eta ^{\ell}|}$, unrolled in a 1D histogram along ${{p_{\mathrm {T}}} ^{\ell}}$ in bins of ${| \eta ^{\ell}|}$ for the positive (negative) charge on top (bottom). The combined muon+electron fit is shown in green markers, the muon-only fit in blue markers, and the electron-only fit is shown in red markers.

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Figure 13-a:
Absolute double-differential cross section as a function of ${{p_{\mathrm {T}}} ^{\ell}}$ and ${| \eta ^{\ell}|}$, unrolled in a 1D histogram along ${{p_{\mathrm {T}}} ^{\ell}}$ in bins of ${| \eta ^{\ell}|}$ for the positive (negative) charge on top (bottom). The combined muon+electron fit is shown in green markers, the muon-only fit in blue markers, and the electron-only fit is shown in red markers.

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Figure 13-b:
Absolute double-differential cross section as a function of ${{p_{\mathrm {T}}} ^{\ell}}$ and ${| \eta ^{\ell}|}$, unrolled in a 1D histogram along ${{p_{\mathrm {T}}} ^{\ell}}$ in bins of ${| \eta ^{\ell}|}$ for the positive (negative) charge on top (bottom). The combined muon+electron fit is shown in green markers, the muon-only fit in blue markers, and the electron-only fit is shown in red markers.

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Figure 14:
Absolute differential cross section as a function of the ${| \eta ^{\ell}|}$ for the $ {\mathrm{W} ^{+}\to \ell \nu} $ channel (left) and $ {\mathrm{W} ^{-}\to \ell \bar\nu} $ channel (middle). The corresponding charge asymmetry is shown on the right. The measurement is the result of the combination of the electron and muon channels. The lower panel in each plot shows the ratio (difference) of observation and expectation for the cross section (asymmetry) and the relative uncertainty.

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Figure 14-a:
Absolute differential cross section as a function of the ${| \eta ^{\ell}|}$ for the $ {\mathrm{W} ^{+}\to \ell \nu} $ channel (left) and $ {\mathrm{W} ^{-}\to \ell \bar\nu} $ channel (middle). The corresponding charge asymmetry is shown on the right. The measurement is the result of the combination of the electron and muon channels. The lower panel in each plot shows the ratio (difference) of observation and expectation for the cross section (asymmetry) and the relative uncertainty.

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Figure 14-b:
Absolute differential cross section as a function of the ${| \eta ^{\ell}|}$ for the $ {\mathrm{W} ^{+}\to \ell \nu} $ channel (left) and $ {\mathrm{W} ^{-}\to \ell \bar\nu} $ channel (middle). The corresponding charge asymmetry is shown on the right. The measurement is the result of the combination of the electron and muon channels. The lower panel in each plot shows the ratio (difference) of observation and expectation for the cross section (asymmetry) and the relative uncertainty.

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Figure 14-c:
Absolute differential cross section as a function of the ${| \eta ^{\ell}|}$ for the $ {\mathrm{W} ^{+}\to \ell \nu} $ channel (left) and $ {\mathrm{W} ^{-}\to \ell \bar\nu} $ channel (middle). The corresponding charge asymmetry is shown on the right. The measurement is the result of the combination of the electron and muon channels. The lower panel in each plot shows the ratio (difference) of observation and expectation for the cross section (asymmetry) and the relative uncertainty.

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Figure 15:
Pulls and constraints of the 60 Hessian variations of the NNPDF3.0 PDF set, and of the $\alpha _S$ parameter, from the combined fit of muon and electron channels. The underlying fit is performed by fixing the W cross sections to their expectation in all helicity and charge processes. The cyan band represents the input values (which all have zero mean and width one), the orange bands show the post-fit expected values, and black points represent the observed pulls and constraint values. The post-fit nuisance parameter values with respect to the prefit values and uncertainties give a $\chi ^2/dof$ of $117/61$.

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Figure 16:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ for the left-handed and right-handed helicity states from the combination of muon and electron channels. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 16-a:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ for the left-handed and right-handed helicity states from the combination of muon and electron channels. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 16-b:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ for the left-handed and right-handed helicity states from the combination of muon and electron channels. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 17:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from three distinct fits: the combination of muon and electron channels (green), the muon-only fit (blue), and the electron-only fit (red) in the top panel. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data in the middle panel, as well as the ratio between the muon-only fit and the electron-only fit in the bottom panel. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 17-a:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from three distinct fits: the combination of muon and electron channels (green), the muon-only fit (blue), and the electron-only fit (red) in the top panel. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data in the middle panel, as well as the ratio between the muon-only fit and the electron-only fit in the bottom panel. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 17-b:
Measured absolute $\mathrm{W} \to \ell ^+\nu $ (left) or $\mathrm{W} \to \ell ^-\bar\nu $ (right) cross section as a function of $ {| Y_{\mathrm{W}} |} $ from three distinct fits: the combination of muon and electron channels (green), the muon-only fit (blue), and the electron-only fit (red) in the top panel. Also shown is the ratio of the prediction from MadGraph 5_aMC@NLO to the data in the middle panel, as well as the ratio between the muon-only fit and the electron-only fit in the bottom panel. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 18:
Measured $A_4$ coefficient for $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) extracted from the fit of the polarized cross sections to the combined electron+muon fit. Also shown is the difference between the prediction from MadGraph 5_aMC@NLO and the measured values. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 18-a:
Measured $A_4$ coefficient for $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) extracted from the fit of the polarized cross sections to the combined electron+muon fit. Also shown is the difference between the prediction from MadGraph 5_aMC@NLO and the measured values. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 18-b:
Measured $A_4$ coefficient for $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) extracted from the fit of the polarized cross sections to the combined electron+muon fit. Also shown is the difference between the prediction from MadGraph 5_aMC@NLO and the measured values. The light-filled band corresponds to the expected uncertainty from the PDF variations, QCD scales and $\alpha _S$.

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Figure 19:
Correlation coefficients between the helicity-dependent signal cross sections for $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) extracted from the fit to the combined electron+muon fit.

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Figure 19-a:
Correlation coefficients between the helicity-dependent signal cross sections for $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) extracted from the fit to the combined electron+muon fit.

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Figure 19-b:
Correlation coefficients between the helicity-dependent signal cross sections for $\mathrm{W} \to \ell ^+\nu $ (left) and $\mathrm{W} \to \ell ^-\bar\nu $ (right) extracted from the fit to the combined electron+muon fit.

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Figure 20:
Correlation coefficients between the 60 PDF nuisance parameters extracted from the fit to the combined electron+muon fit.

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Figure 21:
Post-fit pulls and constraints of the nuisance parameters associated with the QCD scale systematics. The numbering refers to bins in the ${p_{\mathrm {T}} ^{\mathrm{W}}}$ spectrum in increasing order. The nuisance parameters applied to the "left'' polarization are shown on the left while the ones associated with the "right'' polarization are shown on the right.

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Figure 21-a:
Post-fit pulls and constraints of the nuisance parameters associated with the QCD scale systematics. The numbering refers to bins in the ${p_{\mathrm {T}} ^{\mathrm{W}}}$ spectrum in increasing order. The nuisance parameters applied to the "left'' polarization are shown on the left while the ones associated with the "right'' polarization are shown on the right.

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Figure 21-b:
Post-fit pulls and constraints of the nuisance parameters associated with the QCD scale systematics. The numbering refers to bins in the ${p_{\mathrm {T}} ^{\mathrm{W}}}$ spectrum in increasing order. The nuisance parameters applied to the "left'' polarization are shown on the left while the ones associated with the "right'' polarization are shown on the right.

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Figure 22:
Remaining impacts on the normalized polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{+}} _{R}} $ (top), $ {\mathrm{W^{+}} _{L}} $ (middle), and $ {\mathrm{W^{-}} _{R}} $ (bottom).

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Figure 22-a:
Remaining impacts on the normalized polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{+}} _{R}} $ (top), $ {\mathrm{W^{+}} _{L}} $ (middle), and $ {\mathrm{W^{-}} _{R}} $ (bottom).

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Figure 22-b:
Remaining impacts on the normalized polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{+}} _{R}} $ (top), $ {\mathrm{W^{+}} _{L}} $ (middle), and $ {\mathrm{W^{-}} _{R}} $ (bottom).

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Figure 22-c:
Remaining impacts on the normalized polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{+}} _{R}} $ (top), $ {\mathrm{W^{+}} _{L}} $ (middle), and $ {\mathrm{W^{-}} _{R}} $ (bottom).

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Figure 23:
Impacts on the absolute polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{+}} _{L}} $ (top) and $ {\mathrm{W^{+}} _{R}} $ (bottom).

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Figure 23-a:
Impacts on the absolute polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{+}} _{L}} $ (top) and $ {\mathrm{W^{+}} _{R}} $ (bottom).

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Figure 23-b:
Impacts on the absolute polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{+}} _{L}} $ (top) and $ {\mathrm{W^{+}} _{R}} $ (bottom).

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Figure 24:
Impacts on the absolute polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{-}} _{L}} $ (top) and $ {\mathrm{W^{-}} _{R}} $ (bottom).

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Figure 24-a:
Impacts on the absolute polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{-}} _{L}} $ (top) and $ {\mathrm{W^{-}} _{R}} $ (bottom).

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Figure 24-b:
Impacts on the absolute polarized cross sections as a function of the rapidity. Shown are the impacts of the nuisance groups for $ {\mathrm{W^{-}} _{L}} $ (top) and $ {\mathrm{W^{-}} _{R}} $ (bottom).

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Figure 25:
Impacts on the charge asymmetry for $ {\mathrm{W} _{R}} $.

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Figure 26:
Impacts on the unpolarized absolute cross sections for $ {\mathrm{W^{+}}} $ (top), $ {\mathrm{W^{-}}} $ (middle), and the unpolarized charge asymmetry (bottom).

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Figure 26-a:
Impacts on the unpolarized absolute cross sections for $ {\mathrm{W^{+}}} $ (top), $ {\mathrm{W^{-}}} $ (middle), and the unpolarized charge asymmetry (bottom).

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Figure 26-b:
Impacts on the unpolarized absolute cross sections for $ {\mathrm{W^{+}}} $ (top), $ {\mathrm{W^{-}}} $ (middle), and the unpolarized charge asymmetry (bottom).

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Figure 26-c:
Impacts on the unpolarized absolute cross sections for $ {\mathrm{W^{+}}} $ (top), $ {\mathrm{W^{-}}} $ (middle), and the unpolarized charge asymmetry (bottom).

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Figure 27:
Impacts on the unpolarized normalized cross sections for $ {\mathrm{W^{+}}} $ (top) and $ {\mathrm{W^{-}}} $ (bottom).

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Figure 27-a:
Impacts on the unpolarized normalized cross sections for $ {\mathrm{W^{+}}} $ (top) and $ {\mathrm{W^{-}}} $ (bottom).

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Figure 27-b:
Impacts on the unpolarized normalized cross sections for $ {\mathrm{W^{+}}} $ (top) and $ {\mathrm{W^{-}}} $ (bottom).

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Figure 28:
Impacts on the A$_4$ coefficient as a function of $|Y_{\mathrm{W}}|$ for $ {\mathrm{W^{+}}} $ (top) and $ {\mathrm{W^{-}}} $ (bottom).

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Figure 28-a:
Impacts on the A$_4$ coefficient as a function of $|Y_{\mathrm{W}}|$ for $ {\mathrm{W^{+}}} $ (top) and $ {\mathrm{W^{-}}} $ (bottom).

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Figure 28-b:
Impacts on the A$_4$ coefficient as a function of $|Y_{\mathrm{W}}|$ for $ {\mathrm{W^{+}}} $ (top) and $ {\mathrm{W^{-}}} $ (bottom).

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Figure 29:
Unrolled cross section for the combined electron+muon fit unrolled along ${{p_{\mathrm {T}}} ^{\ell}}$ in bins of ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 29-a:
Unrolled cross section for the combined electron+muon fit unrolled along ${{p_{\mathrm {T}}} ^{\ell}}$ in bins of ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 29-b:
Unrolled cross section for the combined electron+muon fit unrolled along ${{p_{\mathrm {T}}} ^{\ell}}$ in bins of ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 30:
Normalized cross sections as a function of ${| \eta ^{\ell} |}$, integrated over ${{p_{\mathrm {T}}} ^{\ell}}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 30-a:
Normalized cross sections as a function of ${| \eta ^{\ell} |}$, integrated over ${{p_{\mathrm {T}}} ^{\ell}}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 30-b:
Normalized cross sections as a function of ${| \eta ^{\ell} |}$, integrated over ${{p_{\mathrm {T}}} ^{\ell}}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 31:
Absolute cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 31-a:
Absolute cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 31-b:
Absolute cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 32:
Normalized cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (middle), and the resulting charge asymmetry (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 32-a:
Normalized cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (middle), and the resulting charge asymmetry (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 32-b:
Normalized cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (middle), and the resulting charge asymmetry (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 32-c:
Normalized cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$ for ${\mathrm{W^{+}}}$ (left) and ${\mathrm{W^{-}}}$ (middle), and the resulting charge asymmetry (right). Shown in the colored bands are the prediction from MadGraph 5_aMC@NLO with the PDF+$\alpha _S$ variations in blue, and the total theoretical uncertainty in bordeaux.

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Figure 33:
Remaining impacts of the nuisance groups on the normalized cross sections as a function of ${| \eta ^{\ell} |}$, integrated in ${{p_{\mathrm {T}}} ^{\ell}}$, for ${\mathrm{W^{-}}}$.

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Figure 34:
Remaining impacts of the nuisance groups on the absolute cross sections as a function of ${| \eta ^{\ell} |}$, integrated in ${{p_{\mathrm {T}}} ^{\ell}}$, for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom).

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Figure 34-a:
Remaining impacts of the nuisance groups on the absolute cross sections as a function of ${| \eta ^{\ell} |}$, integrated in ${{p_{\mathrm {T}}} ^{\ell}}$, for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom).

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Figure 34-b:
Remaining impacts of the nuisance groups on the absolute cross sections as a function of ${| \eta ^{\ell} |}$, integrated in ${{p_{\mathrm {T}}} ^{\ell}}$, for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom).

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Figure 35:
Remaining impacts of the nuisance groups on the normalized cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$, for ${\mathrm{W^{+}}}$ (top), ${\mathrm{W^{-}}}$ (middle), and the resulting charge asymmetry (bottom).

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Figure 35-a:
Remaining impacts of the nuisance groups on the normalized cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$, for ${\mathrm{W^{+}}}$ (top), ${\mathrm{W^{-}}}$ (middle), and the resulting charge asymmetry (bottom).

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Figure 35-b:
Remaining impacts of the nuisance groups on the normalized cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$, for ${\mathrm{W^{+}}}$ (top), ${\mathrm{W^{-}}}$ (middle), and the resulting charge asymmetry (bottom).

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Figure 35-c:
Remaining impacts of the nuisance groups on the normalized cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$, for ${\mathrm{W^{+}}}$ (top), ${\mathrm{W^{-}}}$ (middle), and the resulting charge asymmetry (bottom).

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Figure 36:
Remaining impacts of the nuisance groups on the absolute cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$, for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom).

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Figure 36-a:
Remaining impacts of the nuisance groups on the absolute cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$, for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom).

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Figure 36-b:
Remaining impacts of the nuisance groups on the absolute cross sections as a function of ${{p_{\mathrm {T}}} ^{\ell}}$, integrated over ${| \eta ^{\ell} |}$, for ${\mathrm{W^{+}}}$ (top) and ${\mathrm{W^{-}}}$ (bottom).
Tables

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Table 1:
Estimated background-to-signal ratios in the $\mathrm{W} \to \mu \nu $ and $\mathrm{W} \to \mathrm{e} \nu $ channels. The DY simulation includes $\ell =$ e, $\mu$, $\tau $.

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Table 2:
Systematic uncertainties for each source and process. Quoted numbers correspond to the size of log-normal nuisance parameters applied in the fit, while a "yes'' in a given cell corresponds to the given systematic uncertainty being applied as a shape variation over the full 2D template space.
Summary
A differential measurement of the W boson cross sections, measured as a function of the W boson rapidity, ${| Y_{\mathrm{W}} |} $, and for the two charges separately, ${\mathrm{W^{+}}} \to \ell^+\nu$ and ${\mathrm{W^{-}}} \to \ell^-\bar\nu$, is presented by the CMS Collaboration. Double-differential cross section measurements of the W boson are presented as a function of the charged lepton transverse momentum, ${p_{\mathrm{T}}}^{\ell}$, and lepton pseudorapidity, $|\eta^{\ell}|$. For both measurements, the differential charge asymmetry is also presented. The measurement is based on data taken in pp collisions at the LHC at a center-of-mass energy of $\sqrt{s} = $ 13 TeV with an integrated luminosity of 35.9 fb$^{-1}$ . Differential cross sections are presented both absolute and normalized to the total production cross section within a given acceptance. For the helicity measurement, the range ${| Y_{\mathrm{W}} |} < $ 2.5 is considered, while for the double-differential cross section the range $|\eta^{\ell}| < $ 2.4 and 26 $ < p_{\mathrm{T}}^{\ell} < $ 55 GeV is used. The measurement is performed using both the muon and the electron channels, combined together considering all sources of correlated and uncorrelated uncertainties.

The precision in the measurement as a function of ${| Y_{\mathrm{W}} |} $, using a combination of the two channels, is about 2% in central ${| Y_{\mathrm{W}} |}$ bins, and 5% to 20%, depending on the charge-polarization combination, in the outermost acceptance bins. The precision of the double-differential cross section, relative to the total, is about 1% in each of the 324 bins relative to the central part of the detector, $|\eta^{\ell}| < 1$, and better than 2.5% up to $|\eta^{\ell}| < 2$ for each of the two W charges. Charge asymmetries are also measured, differentially in ${| Y_{\mathrm{W}} |}$ and polarization, as well as in ${p_{\mathrm{T}}}^{\ell}$ and $|\eta^{\ell}|$. The uncertainties in these asymmetries range from 0.1% in high-acceptance regions to roughly 2.5% in regions of phase space with lower detector acceptance.

This measurement is used to constrain PDF parameters in a simultaneous fit of the measurements from the two channels and the two W charges. The constraints are derived at detector level on 60 uncorrelated eigenvalues of the NNPDF3.0 set of PDFs within the MadGraph5+MCatNLO generator code, and show a total constraint down to $\simeq$70% of the pre-fit uncertainties for certain variations of the PDF nuisance parameters.
Additional Figures

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Additional Figure 1:
Distributions of $\eta $ and $p_{\mathrm{T}}$ of the reconstructed muon in W boson decays, split into W boson charge and polarisation (left, longitudinal, right). For a given charge and helicity state, the peculiar shape of each distribution is determined by the underlying W rapidity distribution, which in turn depends on the proton PDFs. These distributions are obtained from simulated $\mathrm{W}(\mu \nu )$+jets events at $\sqrt {s} = $ 13 TeV using MadGraph5\_aMC@NLO. Event yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. No event selection is applied, except for the requirement that a muon is identified and reconstructed within the CMS detector.

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Additional Figure 1-a:
Distributions of $\eta $ and $p_{\mathrm{T}}$ of the reconstructed muon in W boson decays, split into W boson charge and polarisation (left, longitudinal, right). For a given charge and helicity state, the peculiar shape of each distribution is determined by the underlying W rapidity distribution, which in turn depends on the proton PDFs. These distributions are obtained from simulated $\mathrm{W}(\mu \nu )$+jets events at $\sqrt {s} = $ 13 TeV using MadGraph5\_aMC@NLO. Event yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. No event selection is applied, except for the requirement that a muon is identified and reconstructed within the CMS detector.

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Additional Figure 1-b:
Distributions of $\eta $ and $p_{\mathrm{T}}$ of the reconstructed muon in W boson decays, split into W boson charge and polarisation (left, longitudinal, right). For a given charge and helicity state, the peculiar shape of each distribution is determined by the underlying W rapidity distribution, which in turn depends on the proton PDFs. These distributions are obtained from simulated $\mathrm{W}(\mu \nu )$+jets events at $\sqrt {s} = $ 13 TeV using MadGraph5\_aMC@NLO. Event yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. No event selection is applied, except for the requirement that a muon is identified and reconstructed within the CMS detector.

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Additional Figure 1-c:
Distributions of $\eta $ and $p_{\mathrm{T}}$ of the reconstructed muon in W boson decays, split into W boson charge and polarisation (left, longitudinal, right). For a given charge and helicity state, the peculiar shape of each distribution is determined by the underlying W rapidity distribution, which in turn depends on the proton PDFs. These distributions are obtained from simulated $\mathrm{W}(\mu \nu )$+jets events at $\sqrt {s} = $ 13 TeV using MadGraph5\_aMC@NLO. Event yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. No event selection is applied, except for the requirement that a muon is identified and reconstructed within the CMS detector.

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Additional Figure 1-d:
Distributions of $\eta $ and $p_{\mathrm{T}}$ of the reconstructed muon in W boson decays, split into W boson charge and polarisation (left, longitudinal, right). For a given charge and helicity state, the peculiar shape of each distribution is determined by the underlying W rapidity distribution, which in turn depends on the proton PDFs. These distributions are obtained from simulated $\mathrm{W}(\mu \nu )$+jets events at $\sqrt {s} = $ 13 TeV using MadGraph5\_aMC@NLO. Event yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. No event selection is applied, except for the requirement that a muon is identified and reconstructed within the CMS detector.

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Additional Figure 1-e:
Distributions of $\eta $ and $p_{\mathrm{T}}$ of the reconstructed muon in W boson decays, split into W boson charge and polarisation (left, longitudinal, right). For a given charge and helicity state, the peculiar shape of each distribution is determined by the underlying W rapidity distribution, which in turn depends on the proton PDFs. These distributions are obtained from simulated $\mathrm{W}(\mu \nu )$+jets events at $\sqrt {s} = $ 13 TeV using MadGraph5\_aMC@NLO. Event yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. No event selection is applied, except for the requirement that a muon is identified and reconstructed within the CMS detector.

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Additional Figure 1-f:
Distributions of $\eta $ and $p_{\mathrm{T}}$ of the reconstructed muon in W boson decays, split into W boson charge and polarisation (left, longitudinal, right). For a given charge and helicity state, the peculiar shape of each distribution is determined by the underlying W rapidity distribution, which in turn depends on the proton PDFs. These distributions are obtained from simulated $\mathrm{W}(\mu \nu )$+jets events at $\sqrt {s} = $ 13 TeV using MadGraph5\_aMC@NLO. Event yields are normalized to an integrated luminosity of 35.9 fb$^{-1}$. No event selection is applied, except for the requirement that a muon is identified and reconstructed within the CMS detector.

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Additional Figure 2:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

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Additional Figure 2-a:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

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Additional Figure 2-b:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

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Additional Figure 3:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

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Additional Figure 3-a:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 3-b:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

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Additional Figure 4:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 4-a:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 4-b:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 5:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 5-a:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 5-b:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 6:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 6-a:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 6-b:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 7:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 7-a:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 7-b:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 8:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 8-a:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.

png pdf
Additional Figure 8-b:
The post-fit nuisance parameter values and covariance matrix for the PDF and alphaS uncertainties from the fixed-parameter-of-interest fit described in Section 8.2 are propagated to the corresponding change in central value and uncertainty with respect to the input NNPDF3.0 NLO PDF set as a function of $x$ for fixed $Q^2=M_{\mathrm{W}}^2$. The profiling procedure employed here has the caveat that the results cannot be interpreted as a rigorous PDF determination in case the results are far from the input PDF, and that the measurement under consideration tends to have a larger weight than if it were included in a global PDF determination. Nevertheless the profiling procedure is useful to assess the sensitivity of the different parton distributions to this measurement, and its compatibility with the predictions of the input PDF set. Particular to this result is the fact that constraints are derived only at NLO + parton shower accuracy in QCD, and that there are possible limitations of the PDF set used with respect to newer sets. The presence of oscillatory behaviour in the valence quark distributions is in part related to anti-correlations between different $x$ values arising from the statistical uncertainties in the underlying measurement.
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Compact Muon Solenoid
LHC, CERN