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| CMS-PAS-SMP-19-011 | ||
| Differential cross section measurements of the production of Z bosons and charm jets at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| July 2020 | ||
| Abstract: Measurements of differential cross sections of the production of a Z boson in association with at least one jet initiated by a charm quark in proton-proton collisions at $\sqrt{s}= $ 13 TeV are presented. The data were recorded in 2016 by the CMS experiment at the LHC and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The measurements are performed in final states that include a pair of electrons or muons consistent with being the decay products of a Z boson, plus a jet consistent with being initiated by a charm quark produced in the hard interaction. Differential cross sections with respect to the transverse momentum of the Z boson candidate or the charm jet are measured, and compared with predictions from different Monte Carlo generators. The inclusive production cross section in the fiducial region is also presented. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 04 (2021) 109. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Example Feynman diagram for the Z+c-jet process. |
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Figure 2:
Distribution of the secondary vertex mass of the highest-${{p_{\mathrm {T}}}}$ c-tagged central jet, for muon (left) and electron (right) channels.The observed data is compared to the different signal and background components in simulation, before normalization scale factors are applied. |
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Figure 2-a:
Distribution of the secondary vertex mass of the highest-${{p_{\mathrm {T}}}}$ c-tagged central jet, for muon (left) and electron (right) channels.The observed data is compared to the different signal and background components in simulation, before normalization scale factors are applied. |
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Figure 2-b:
Distribution of the secondary vertex mass of the highest-${{p_{\mathrm {T}}}}$ c-tagged central jet, for muon (left) and electron (right) channels.The observed data is compared to the different signal and background components in simulation, before normalization scale factors are applied. |
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Figure 3:
The distributions of ${p_{\mathrm {T}}}$ in data and corrected simulation, after applying the fitted scale factors to the Drell-Yan components. The upper plots show distributions for the muon channel, with the ${p_{\mathrm {T}}}$ of the muon pair (left) and c-tagged jet (right). The lower plots show distributions for the electron channel with the ${p_{\mathrm {T}}}$ of the electron pair (left) and c-tagged jet (right). |
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Figure 3-a:
The distributions of ${p_{\mathrm {T}}}$ in data and corrected simulation, after applying the fitted scale factors to the Drell-Yan components. The upper plots show distributions for the muon channel, with the ${p_{\mathrm {T}}}$ of the muon pair (left) and c-tagged jet (right). The lower plots show distributions for the electron channel with the ${p_{\mathrm {T}}}$ of the electron pair (left) and c-tagged jet (right). |
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Figure 3-b:
The distributions of ${p_{\mathrm {T}}}$ in data and corrected simulation, after applying the fitted scale factors to the Drell-Yan components. The upper plots show distributions for the muon channel, with the ${p_{\mathrm {T}}}$ of the muon pair (left) and c-tagged jet (right). The lower plots show distributions for the electron channel with the ${p_{\mathrm {T}}}$ of the electron pair (left) and c-tagged jet (right). |
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Figure 3-c:
The distributions of ${p_{\mathrm {T}}}$ in data and corrected simulation, after applying the fitted scale factors to the Drell-Yan components. The upper plots show distributions for the muon channel, with the ${p_{\mathrm {T}}}$ of the muon pair (left) and c-tagged jet (right). The lower plots show distributions for the electron channel with the ${p_{\mathrm {T}}}$ of the electron pair (left) and c-tagged jet (right). |
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Figure 3-d:
The distributions of ${p_{\mathrm {T}}}$ in data and corrected simulation, after applying the fitted scale factors to the Drell-Yan components. The upper plots show distributions for the muon channel, with the ${p_{\mathrm {T}}}$ of the muon pair (left) and c-tagged jet (right). The lower plots show distributions for the electron channel with the ${p_{\mathrm {T}}}$ of the electron pair (left) and c-tagged jet (right). |
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Figure 4:
Fraction of selected Z+c-jet events originating inside the fiducial phase space, as a function of ${p_{\mathrm {T}}}$. The plots show the distributions in the muon and electron channels, as a function of ${p_{\mathrm {T}}}$ of the Z candidate (left) and c-tagged jet (right). |
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Figure 4-a:
Fraction of selected Z+c-jet events originating inside the fiducial phase space, as a function of ${p_{\mathrm {T}}}$. The plots show the distributions in the muon and electron channels, as a function of ${p_{\mathrm {T}}}$ of the Z candidate (left) and c-tagged jet (right). |
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Figure 4-b:
Fraction of selected Z+c-jet events originating inside the fiducial phase space, as a function of ${p_{\mathrm {T}}}$. The plots show the distributions in the muon and electron channels, as a function of ${p_{\mathrm {T}}}$ of the Z candidate (left) and c-tagged jet (right). |
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Figure 5:
Efficiency as a function of ${p_{\mathrm {T}}}$. The plots show the distributions in the muon and electron channels, as a function of ${p_{\mathrm {T}}}$ of the Z boson (left) and c-jet (right). |
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Figure 5-a:
Efficiency as a function of ${p_{\mathrm {T}}}$. The plots show the distributions in the muon and electron channels, as a function of ${p_{\mathrm {T}}}$ of the Z boson (left) and c-jet (right). |
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Figure 5-b:
Efficiency as a function of ${p_{\mathrm {T}}}$. The plots show the distributions in the muon and electron channels, as a function of ${p_{\mathrm {T}}}$ of the Z boson (left) and c-jet (right). |
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Figure 6:
Measured fiducial differential cross sections for inclusive Z+c-jet production, ${\mathrm{d}\sigma \over {\mathrm{d} {p_{\mathrm {T}}} (\text { c jet})}}$ (left) and ${\mathrm{d}\sigma \over {\mathrm{d} {p_{\mathrm {T}}} (\mathrm{Z})}}$ (right). |
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Figure 6-a:
Measured fiducial differential cross sections for inclusive Z+c-jet production, ${\mathrm{d}\sigma \over {\mathrm{d} {p_{\mathrm {T}}} (\text { c jet})}}$ (left) and ${\mathrm{d}\sigma \over {\mathrm{d} {p_{\mathrm {T}}} (\mathrm{Z})}}$ (right). |
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Figure 6-b:
Measured fiducial differential cross sections for inclusive Z+c-jet production, ${\mathrm{d}\sigma \over {\mathrm{d} {p_{\mathrm {T}}} (\text { c jet})}}$ (left) and ${\mathrm{d}\sigma \over {\mathrm{d} {p_{\mathrm {T}}} (\mathrm{Z})}}$ (right). |
| Tables | |
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Table 1:
Values of Z+light-jet, Z+c-jet, and Z+b-jet scale factors measured in the muon channel, as a function of c-tagged jet ${p_{\mathrm {T}}}$. The first uncertainty in each case is the statistical uncertainty from the fit, the second the systematic uncertainty. |
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Table 2:
Values of Z+light-jet, Z+c-jet, and Z+b-jet scale factors measured in the electron channel, as a function of c-tagged jet ${p_{\mathrm {T}}}$. The first uncertainty in each case is the statistical uncertainty from the fit, the second the systematic uncertainty. |
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Table 3:
Values of Z+light-jet, Z+c-jet, and Z+b-jet scale factors measured in the muon channel, as a function of Z candidate ${p_{\mathrm {T}}}$. The first uncertainty in each case is the statistical uncertainty from the fit, the second the systematic uncertainty. |
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Table 4:
Values of Z+light-jet, Z+c-jet, and Z+b-jet scale factors measured in the electron channel, as a function of Z candidate ${p_{\mathrm {T}}}$. The first uncertainty in each case is the statistical uncertainty from the fit, the second the systematic uncertainty. |
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Table 5:
Summary of the systematic uncertainties on the inclusive fiducial cross section arising from the various sources considered. |
| Summary |
| Differential cross sections for inclusive Z+c-jet production with respect to the transverse momentum of the Z boson and the c jet have been measured in proton-proton collisions at $\sqrt{s} = $ 13 TeV using 35.9 fb$^{-1}$ of data collected by the CMS experiment at the LHC. The measurements pertain to a fiducial space defined as containing a c jet with ${p_{\mathrm{T}}} > $ 30 GeV and $|\eta| < $ 2.4, and a pair of leptons with ${p_{\mathrm{T}}} > $ 26 GeV for leading lepton, ${p_{\mathrm{T}}} > $ 10 GeV for subleading lepton and $|\eta| < $ 2.4, and an invariant mass of the two leptons between 71 and 111 GeV. The main backgrounds considered were Z+light-jet, Z+b-jet, top pair, and diboson production. Unfolding was used to take into account detector effects. The inclusive fiducial cross-section value for signal with Z ${p_{\mathrm{T}}} $ < 300 GeV was found to be 413.5 $\pm$ 5.6 (stat) $\pm$ 19.5 (exp) $\pm$ 5.9 (th) pb, with MadGraph5+MCatNLO at next-to-leading order predicting 524.9 $\pm$ 11.7 (th) pb for the same fiducial region. The predictions from several generators were compared with measurements. The prediction from MadGraph5+MCatNLO at leading order shows better agreement with data, while MadGraph5+MCatNLO at next-to-leading order and SHERPA tend to overestimate the cross section value. These results are sensitive to the PDF of the charm quark and can improve the existing constraints. |
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