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| CMS-HIN-17-007 ; CERN-EP-2018-283 | ||
| Observation of nuclear modifications in ${\mathrm{W^{\pm}}}$ boson production in pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV | ||
| CMS Collaboration | ||
| 4 May 2019 | ||
| Phys. Lett. B 800 (2020) 135048 | ||
| Abstract: The production of ${\mathrm{W^{\pm}}}$ bosons is studied in proton-lead pPb collisions at a nucleon-nucleon centre-of-mass energy of ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV. Measurements are performed in the ${\mathrm{W^{\pm}}\to\mu^{\pm}\nu_{\mu}}$ channel using a data sample corresponding to an integrated luminosity of 173.4 $\pm$ 8.7 nb$^{-1}$, collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame $|{{{\eta_{\text{lab}}} ^{\mu}} }| < $ 2.4 and transverse momentum $|{p_{\mathrm{T}}}^{\mu} > $ 25 GeV/$c$. The ${\mathrm{W^{\pm}}}$ boson differential cross sections, muon charge asymmetry, and the ratios of ${\mathrm{W^{\pm}}}$ boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits. | ||
| Links: e-print arXiv:1905.01486 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
|---|
| Figures | |
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Figure 1:
The missing transverse momentum ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for ${{\mathrm {W^-}}\to {\mu ^-} {\overline {\nu}_ {\mu}}}$ events within the $-0.2 < {{\eta _{\text {CM}}} ^{{\mu}}} < 0.0$ (left) range and for ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$ events within the 1.80 $ < {{\eta _{\text {CM}}} ^{{\mu}}} < $ 1.93 (right) range. Unbinned fits to the data (black points) are performed with six contributions, stacked from bottom to top: ${{\mathrm {t}\overline {\mathrm {t}}}}$ (orange), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{\tau}^{+} {\tau}^{-}}}$ (dark blue), ${ {\mathrm {W}^{\pm}} \to {\tau} ^{\pm} {\nu _ {\tau}} }$ (red), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{{\mu ^+}} {{\mu ^-}}}}$ (green), QCD multijet (light blue) and ${{\mathrm {W}^{\pm}} \to {\mu ^\pm} {\nu _ {\mu}}}$ (yellow). The ${{\eta _{\text {CM}}} ^{{\mu}}}$ regions are defined such that the proton is moving towards positive pseudorapidity. Error bars represent statistical uncertainties. The lower panels display the data divided by the result of the fit. |
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Figure 1-a:
The missing transverse momentum ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for ${{\mathrm {W^-}}\to {\mu ^-} {\overline {\nu}_ {\mu}}}$ events within the $-0.2 < {{\eta _{\text {CM}}} ^{{\mu}}} < 0.0$ range. Unbinned fits to the data (black points) are performed with six contributions, stacked from bottom to top: ${{\mathrm {t}\overline {\mathrm {t}}}}$ (orange), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{\tau}^{+} {\tau}^{-}}}$ (dark blue), ${ {\mathrm {W}^{\pm}} \to {\tau} ^{\pm} {\nu _ {\tau}} }$ (red), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{{\mu ^+}} {{\mu ^-}}}}$ (green), QCD multijet (light blue) and ${{\mathrm {W}^{\pm}} \to {\mu ^\pm} {\nu _ {\mu}}}$ (yellow). The ${{\eta _{\text {CM}}} ^{{\mu}}}$ regions are defined such that the proton is moving towards positive pseudorapidity. Error bars represent statistical uncertainties. The lower panel displays the data divided by the result of the fit. |
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Figure 1-b:
The missing transverse momentum ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$ events within the 1.80 $ < {{\eta _{\text {CM}}} ^{{\mu}}} < $ 1.93 range. Unbinned fits to the data (black points) are performed with six contributions, stacked from bottom to top: ${{\mathrm {t}\overline {\mathrm {t}}}}$ (orange), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{\tau}^{+} {\tau}^{-}}}$ (dark blue), ${ {\mathrm {W}^{\pm}} \to {\tau} ^{\pm} {\nu _ {\tau}} }$ (red), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{{\mu ^+}} {{\mu ^-}}}}$ (green), QCD multijet (light blue) and ${{\mathrm {W}^{\pm}} \to {\mu ^\pm} {\nu _ {\mu}}}$ (yellow). The ${{\eta _{\text {CM}}} ^{{\mu}}}$ regions are defined such that the proton is moving towards positive pseudorapidity. Error bars represent statistical uncertainties. The lower panel displays the data divided by the result of the fit. |
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Figure 2:
Differential production cross sections for ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$ (left) and ${{\mathrm {W^-}}\to {\mu ^-} {\overline {\nu}_ {\mu}}}$ (right), as a function of the muon pseudorapidity in the centre-of-mass frame. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The global integrated luminosity uncertainty of $\pm $3.5% is not shown. The NLO calculations with CT14 PDF, and CT14+EPPS16 and CT14+nCTEQ15 nPDFs, are also displayed, including their 68% confidence interval PDF uncertainty bands. The bottom panels show the ratio of data, CT14+EPPS16 and CT14+nCTEQ15 with respect to CT14. |
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Figure 2-a:
Differential production cross sections for ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$, as a function of the muon pseudorapidity in the centre-of-mass frame. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The global integrated luminosity uncertainty of $\pm $3.5% is not shown. The NLO calculations with CT14 PDF, and CT14+EPPS16 and CT14+nCTEQ15 nPDFs, are also displayed, including their 68% confidence interval PDF uncertainty bands. The bottom panel shows the ratio of data, CT14+EPPS16 and CT14+nCTEQ15 with respect to CT14. |
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Figure 2-b:
Differential production cross sections for ${{\mathrm {W^-}}\to {\mu ^-} {\overline {\nu}_ {\mu}}}$, as a function of the muon pseudorapidity in the centre-of-mass frame. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The global integrated luminosity uncertainty of $\pm $3.5% is not shown. The NLO calculations with CT14 PDF, and CT14+EPPS16 and CT14+nCTEQ15 nPDFs, are also displayed, including their 68% confidence interval PDF uncertainty bands. The bottom panel shows the ratio of data, CT14+EPPS16 and CT14+nCTEQ15 with respect to CT14. |
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Figure 3:
Forward-backward ratios, ${N_{{\mu}}^{\pm}(+ {{\eta _{\text {CM}}} ^{{\mu}}})/N_{{\mu}}^{\pm}(- {{\eta _{\text {CM}}} ^{{\mu}}})}$, for the positively (left) and negatively (middle) charged muons, and the forward-backward ratio for muons of both signs, ${N_{{\mu}}(+ {{\eta _{\text {CM}}} ^{{\mu}}})/N_{{\mu}}(- {{\eta _{\text {CM}}} ^{{\mu}}})}$ (right), as a function of ${{\eta _{\text {CM}}} ^{{\mu}}}$. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The NLO calculations with CT14 PDF, CT14+EPPS16 nPDF, and CT14+nCTEQ15 nPDF, are also displayed, including their 68% confidence interval PDF uncertainty bands. |
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Figure 3-a:
Forward-backward ratios, ${N_{{\mu}}^{\pm}(+ {{\eta _{\text {CM}}} ^{{\mu}}})/N_{{\mu}}^{\pm}(- {{\eta _{\text {CM}}} ^{{\mu}}})}$, for the positively charged muons, as a function of ${{\eta _{\text {CM}}} ^{{\mu}}}$. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The NLO calculations with CT14 PDF, CT14+EPPS16 nPDF, and CT14+nCTEQ15 nPDF, are also displayed, including their 68% confidence interval PDF uncertainty bands. |
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Figure 3-b:
Forward-backward ratios, ${N_{{\mu}}^{\pm}(+ {{\eta _{\text {CM}}} ^{{\mu}}})/N_{{\mu}}^{\pm}(- {{\eta _{\text {CM}}} ^{{\mu}}})}$, for the negatively charged muons, as a function of ${{\eta _{\text {CM}}} ^{{\mu}}}$. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The NLO calculations with CT14 PDF, CT14+EPPS16 nPDF, and CT14+nCTEQ15 nPDF, are also displayed, including their 68% confidence interval PDF uncertainty bands. |
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Figure 3-c:
Forward-backward ratio for muons of both signs, ${N_{{\mu}}(+ {{\eta _{\text {CM}}} ^{{\mu}}})/N_{{\mu}}(- {{\eta _{\text {CM}}} ^{{\mu}}})}$, as a function of ${{\eta _{\text {CM}}} ^{{\mu}}}$. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The NLO calculations with CT14 PDF, CT14+EPPS16 nPDF, and CT14+nCTEQ15 nPDF, are also displayed, including their 68% confidence interval PDF uncertainty bands. |
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Figure 4:
Muon charge asymmetry, ${(N_{{\mu}}^{+} - N_{{\mu}}^{-})/(N_{{\mu}}^{+} + N_{{\mu}}^{-})}$, as a function of the muon pseudorapidity in the centre-of-mass frame. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The NLO calculations with CT14 PDF, CT14+EPPS16 nPDF, and CT14+nCTEQ15 nPDF, are also displayed, including their 68% confidence interval PDF uncertainty bands. |
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Figure 5:
Comparison of the muon charge asymmetry measured at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV (circles) and at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV [13] (squares). The muon pseudorapidity of the measurements at 5.02 TeV has been shifted (see text for details) [54]. The small horizontal lines represent the statistical and systematic uncertainties summed in quadrature, whereas the error bars show the statistical uncertainties only. The NLO calculations with CT14+EPPS16 nPDF at 8.16 TeV and at 5.02 TeV, are also displayed, including their 68% confidence interval PDF uncertainty bands. |
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Figure 6:
Distribution of the $\chi ^2$/dof values from the comparison of data (cross section measurements) and theoretical calculations, for the CT14, nCTEQ15, and EPPS16 individual error sets. The vertical dashed lines represent the prediction corresponding to the central set of CT14, nCTEQ15, and EPPS16. |
| Tables | |
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Table 1:
Maximum uncertainty in the measured observables among the ${{\eta _{\text {CM}}} ^{{\mu}}}$ bins determined for each source. The uncertainties in the cross sections are relative, whereas those for the asymmetries are absolute. The global integrated luminosity uncertainty of $\pm $3.5% is not included in the total systematic uncertainty in the cross sections. |
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Table 2:
Results of the $\chi ^{2}$ statistical test between the measurements and the nPDF calculations from the CT14 PDF, CT14+EPPS16 nPDF, and CT14+nCTEQ15 nPDF sets. The value of the $\chi ^{2}$, the number of degrees of freedom (dof) and the $\chi ^{2}$ probability (Prob.), are presented for the ${{\mathrm {W}^{\pm}}}$ boson differential cross sections, the muon charge asymmetries, the charged muon forward-backward ratios, and the forward-backward ratios of all muons, respectively. |
| Summary |
|
A study of ${\mathrm{W^{\pm}}}$ boson production in pPb collisions at a nucleon-nucleon centre-of-mass energy of ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV is reported, using the muon decay channel for muons with transverse momenta greater than 25 GeV/$c$ and for absolute values of the pseudorapidity in the laboratory frame $|{{{\eta_{\text{lab}}} ^{\mu}} } < $ 2.4. The differential production cross sections for positively and negatively charged ${\mathrm{W}\to\mu\nu_{\mu}}$ decays, the muon charge asymmetry, and the muon forward-backward ratios, are measured as functions of the muon pseudorapidity in the centre-of-mass frame, in the range $-2.86 < {{\eta_{\text{CM}}} ^{\mu}} < 1.93$. The measurements are compared to theoretical predictions from both proton parton distribution functions (PDFs) (CT14) and nuclear PDF (CT14+EPPS16, CT14+nCTEQ15) sets. The cross sections and the forward-backward asymmetries exhibit significant deviations from the CT14 prediction, revealing nuclear modifications of the PDFs unambiguously for the first time in the production of electroweak bosons in nuclear collisions. Both the CT14+EPPS16, and the CT14+nCTEQ15 calculations show a good overall agreement with the data, with the measurements favouring the former nPDF set. In the latter case, only the individual sets that exhibit the smallest nuclear PDF modifications at small values of $x$ (in the shadowing region) turn out to be compatible with experimental measurements. The small experimental uncertainties allow for a significant reduction in the current uncertainties on the quark and antiquark nuclear PDFs in the range $10^{-3} \lesssim x \lesssim 10^{-1}$. |
| Additional Figures | |
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Additional Figure 1:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ (left) and $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ (right) measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
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Additional Figure 1-a:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
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Additional Figure 1-b:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
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Additional Figure 2:
Comparison of the muon charge asymmetry measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
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Additional Figure 3:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in two muon pseudorapidity regions: $\eta _{\mathrm {CM}} < $ 0 (left plot) and $\eta _{\mathrm {CM}} > $ 0 (right plot). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. |
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Additional Figure 3-a:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in pseudorapidity region $\eta _{\mathrm {CM}} < $ 0. The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. |
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Additional Figure 3-b:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in pseudorapidity region $\eta _{\mathrm {CM}} > $ 0. The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. |
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Additional Figure 4:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in two muon pseudorapidity regions: $\eta _{\mathrm {CM}} < $ 0 (left plot) and $\eta _{\mathrm {CM}} > $ 0 (right plot). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. |
png pdf |
Additional Figure 4-a:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in two muon pseudorapidity regions: $\eta _{\mathrm {CM}} < $ 0 (left plot) and $\eta _{\mathrm {CM}} > $ 0 (right plot). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. |
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Additional Figure 4-b:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in two muon pseudorapidity regions: $\eta _{\mathrm {CM}} < $ 0 (left plot) and $\eta _{\mathrm {CM}} > $ 0 (right plot). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. |
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Additional Figure 5:
Comparison of the muon charge asymmetry measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The muon pseudorapidity has been shifted according to ${= {{\eta _{\text {CM}}} ^{{\mu}}} }$ $\pm $ ln (8.16 TeV). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. |
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Additional Figure 6:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in two muon pseudorapidity regions: $\eta _{\mathrm {CM}} < $ 0 (left plot) and $\eta _{\mathrm {CM}} > $ 0 (right plot). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
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Additional Figure 6-a:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in the muon pseudorapidity region $\eta _{\mathrm {CM}} < $ 0. The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
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Additional Figure 6-b:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in the muon pseudorapidity region $\eta _{\mathrm {CM}} > $ 0. The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
png pdf |
Additional Figure 7:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in two muon pseudorapidity regions: $\eta _{\mathrm {CM}} < $ 0 (left plot) and $\eta _{\mathrm {CM}} > $ 0 (right plot). The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
png pdf |
Additional Figure 7-a:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in the muon pseudorapidity region $\eta _{\mathrm {CM}} < $ 0. The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
png pdf |
Additional Figure 7-b:
Comparison of the production cross section for $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ measured at 8.16 TeV (black points) and at 5.02 TeV [Phys. Lett. B 750 (2015) 565] (blue squares). The comparison is presented in the muon pseudorapidity region $\eta _{\mathrm {CM}} > $ 0. The brackets represent the statistical and systematic uncertainties summed in quadrature, while the error bars show the statistical uncertainties only. The global luminosity uncertainty of $\pm $3.5% for the data at 8.16 TeV and at 5.02 TeV are not shown. Calculations using with CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)] at 8.16 TeV (green line) and at 5.02 TeV (brown line), are also displayed, including their PDF uncertainty bands at 68% confidence interval. |
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Additional Figure 8:
Distribution of the $\chi ^2$/ndf values from the comparison of data (muon charge asymmetry) and theoretical calculations, for the CT14 [Phys. Rev. D 93, 033006 (2016)], nCTEQ15 [Phys. Rev. D 93, 085037 (2016)] and EPPS16 [Eur. Phys. J. C 77, 163 (2017)] individual sets. The vertical dashed lines represent the prediction corresponding to the central set of CT14, nCTEQ15, and EPPS16. |
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Additional Figure 9:
Distribution of the $\chi ^2$/ndf values from the comparison of data (muon forward-backward ratio) and theoretical calculations, for the CT14 [Phys. Rev. D 93, 033006 (2016)], nCTEQ15 [Phys. Rev. D 93, 085037 (2016)] and EPPS16 [Eur. Phys. J. C 77, 163 (2017)] individual sets. The vertical dashed lines represent the prediction corresponding to the central set of CT14, nCTEQ15, and EPPS16. |
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Additional Figure 10:
Distribution of the $\chi ^2$/ndf values from the comparison of data (forward-backward ratio of all muons) and theoretical calculations, for the CT14 [Phys. Rev. D 93, 033006 (2016)], nCTEQ15 [Phys. Rev. D 93, 085037 (2016)] and EPPS16 [Eur. Phys. J. C 77, 163 (2017)] individual sets. The vertical dashed lines represent the prediction corresponding to the central set of CT14, nCTEQ15, and EPPS16. |
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Additional Figure 11:
Distribution of the simulated Bjorken x in the Pb ion as a function of the muon pseudorapidity for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ (left) and $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ (right) generated at 8.16 TeV. The W boson production have been simulated using the NLO generator POWHEG v2 with the POWHEG BOX W.ew.BMNNP using the CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)]. |
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Additional Figure 11-a:
Distribution of the simulated Bjorken x in the Pb ion as a function of the muon pseudorapidity for $\mathrm {W}\rightarrow \mu ^{-}\bar{\nu}_{\mu}$ generated at 8.16 TeV. The W boson production have been simulated using the NLO generator POWHEG v2 with the POWHEG BOX W.ew.BMNNP using the CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)]. |
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Additional Figure 11-b:
Distribution of the simulated Bjorken x in the Pb ion as a function of the muon pseudorapidity for $\mathrm {W}\rightarrow \mu ^{+}\nu _{\mu}$ generated at 8.16 TeV. The W boson production have been simulated using the NLO generator POWHEG v2 with the POWHEG BOX W.ew.BMNNP using the CT14+EPPS16 nPDF [Eur. Phys. J. C 77, 163 (2017)]. |
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Additional Figure 12:
Correlation matrix of the W boson production cross section measurements. The statistical and systematic uncertainties have been included except for the luminosity uncertainty. The black lines are used to distinguish the different bins of muon charge which are ordered from top to bottom as: Minus-Minus, Minus-Plus, Plus-Minus and Plus-Plus. |
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Additional Figure 13:
The missing transverse momentum ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for ${{\mathrm {W^-}}\to {\mu ^-} {\overline {\nu}_ {\mu}}}$ events within the $-0.2 < {{\eta _{\text {CM}}} ^{{\mu}}} < 0.0 $ (left) range and for ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$ events within the 1.80 $ < {{\eta _{\text {CM}}} ^{{\mu}}} < $ 1.93 (right) range, presented in log-scale. Unbinned fits to the data (black points) are performed with six contributions, stacked from bottom to top: ${{\mathrm {t}\overline {\mathrm {t}}}}$ (orange), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{\tau}^{+} {\tau}^{-}}}$ (dark blue), (red), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{{\mu ^+}} {{\mu ^-}}}}$ (green), QCD multijet (light blue) and ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$ (yellow). The ${{\eta _{\text {CM}}} ^{{\mu}}}$ regions are defined such that the proton is moving towards positive pseudorapidity. Error bars represent statistical uncertainties. The lower panels display the data divided by the result of the fit, for each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. |
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Additional Figure 13-a:
The missing transverse momentum ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for ${{\mathrm {W^-}}\to {\mu ^-} {\overline {\nu}_ {\mu}}}$ events within the $-0.2 < {{\eta _{\text {CM}}} ^{{\mu}}} < 0.0 $ range, presented in log-scale. Unbinned fits to the data (black points) are performed with six contributions, stacked from bottom to top: ${{\mathrm {t}\overline {\mathrm {t}}}}$ (orange), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{\tau}^{+} {\tau}^{-}}}$ (dark blue), (red), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{{\mu ^+}} {{\mu ^-}}}}$ (green), QCD multijet (light blue) and ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$ (yellow). The ${{\eta _{\text {CM}}} ^{{\mu}}}$ regions are defined such that the proton is moving towards positive pseudorapidity. Error bars represent statistical uncertainties. The lower panel displays the data divided by the result of the fit, for each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. |
png pdf |
Additional Figure 13-b:
The missing transverse momentum ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$ events within the 1.80 $ < {{\eta _{\text {CM}}} ^{{\mu}}} < $ 1.93 range, presented in log-scale. Unbinned fits to the data (black points) are performed with six contributions, stacked from bottom to top: ${{\mathrm {t}\overline {\mathrm {t}}}}$ (orange), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{\tau}^{+} {\tau}^{-}}}$ (dark blue), (red), ${{{\mathrm {Z}} / {\gamma}^{*}} \to {{{\mu ^+}} {{\mu ^-}}}}$ (green), QCD multijet (light blue) and ${{\mathrm {W^+}}\to {\mu ^+} {\nu _ {\mu}}}$ (yellow). The ${{\eta _{\text {CM}}} ^{{\mu}}}$ regions are defined such that the proton is moving towards positive pseudorapidity. Error bars represent statistical uncertainties. The lower panel displays the data divided by the result of the fit, for each ${{p_{\mathrm {T}}} ^\text {miss}}$ bin. |
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