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| CMS-PAS-TOP-16-022 | ||
| Measurement of the top quark mass with muon+jets final states in pp collisions at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| March 2017 | ||
| Abstract: The mass of the top quark is measured using a sample of $\rm{t}\bar{\rm t}$ candidate events with one muon and at least four jets in the final state, collected by CMS in pp collisions at $\sqrt{s}= $ 13 TeV at the CERN LHC. The candidate events are selected from data corresponding to an integrated luminosity of 2.2 fb$^{-1}$. For each event the mass is reconstructed from a kinematic fit of the decay products to a $\rm{t}\bar{\rm t}$ hypothesis. The top quark mass is determined simultaneously with an overall jet energy scale factor (JSF), constrained by the known mass of the W boson in $\rm{q}\bar{\rm q}$ decays. The estimator is calibrated on samples simulated at next-to-leading order matched to parton shower. The top quark mass is measured to be 172.62 $\pm$ 0.38 (stat.+JSF) $\pm$ 0.70 (syst.) GeV. | ||
| Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
(a) Invariant mass $m_\mathrm{ W } ^\text {reco}$ of the two untagged jets and (b) the invariant mass $ {m_{\mathrm{ t } }} ^\text {reco}$ of the two untagged jets and one of the b-tagged jets after the b tagging requirement. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties considered in Sec. 4 added in quadrature. The lower portion of each panel show the ratio of the yields between the collision data and the simulation. The simulations are normalized to the luminosity. |
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Figure 1-a:
The invariant mass $m_\mathrm{ W } ^\text {reco}$ of the two untagged jets. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties considered in Sec. 4 added in quadrature. The lower portion of the panel shows the ratio of the yields between the collision data and the simulation. The simulations are normalized to the luminosity. |
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Figure 1-b:
The invariant mass $ {m_{\mathrm{ t } }} ^\text {reco}$ of the two untagged jets and one of the b-tagged jets after the b tagging requirement. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties considered in Sec. 4 added in quadrature. The lower portion of the panel shows the ratio of the yields between the collision data and the simulation. The simulations are normalized to the luminosity. |
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Figure 2:
(a) The reconstructed W boson masses $m_\mathrm{ W } ^\text {reco}$ and (b) the fitted top quark masses $ {m_{\mathrm{ t } }} ^\text {fit}$ after the goodness-of-fit selection and the weighting by $P_\mathrm {gof}$. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties added in quadrature. The lower portion of each panel show the ratio of the yields between the collision data and the simulation. |
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Figure 2-a:
The reconstructed W boson masses $m_\mathrm{ W } ^\text {reco}$. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties added in quadrature. The lower portion of the panel shows the ratio of the yields between the collision data and the simulation. |
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Figure 2-b:
The fitted top quark masses $ {m_{\mathrm{ t } }} ^\text {fit}$ after the goodness-of-fit selection and the weighting by $P_\mathrm {gof}$. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties added in quadrature. The lower portion of the panel shows the ratio of the yields between the collision data and the simulation. |
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Figure 3:
(a) Mean difference between the calibrated and generated values of $ {m_{\mathrm{ t } }} $ and JSF as a function of different generated $m_{\mathrm{ t } ,\text {gen}}$ and five values of JSF; (b) width of the pull distributions after the calibration. The colored dashed lines correspond to straight line fits, the black solid line corresponds to a constant fit to all calibration points. The error bars in (a) indicate the statistical uncertainty on the mean difference. |
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Figure 3-a:
Mean difference between the calibrated and generated values of $ {m_{\mathrm{ t } }} $ and JSF as a function of different generated $m_{\mathrm{ t } ,\text {gen}}$ and five values of JSF. The colored dashed lines correspond to straight line fits, the black solid line corresponds to a constant fit to all calibration points. The error bars indicate the statistical uncertainty on the mean difference. |
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Figure 3-b:
Width of the pull distributions after the calibration. The colored dashed lines correspond to straight line fits, the black solid line corresponds to a constant fit to all calibration points. The error bars indicate the statistical uncertainty on the mean difference. |
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Figure 4:
(a) The likelihood ($-2 \Delta \log\left (\mathcal {L}\right )$) measured for the muon+jets final state. The ellipses correspond to contours of $-2 \Delta \log\left (\mathcal {L}\right ) = $ 1 (4, 9) allowing the construction one (two, three) $\sigma $ statistical intervals of $ {m_{\mathrm{ t } }} $. (b) The statistical uncertainty distribution obtained from pseudo-experiments is compared to the uncertainty of the measurement in data. |
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Figure 4-a:
The likelihood ($-2 \Delta \log\left (\mathcal {L}\right )$) measured for the muon+jets final state. The ellipses correspond to contours of $-2 \Delta \log\left (\mathcal {L}\right ) = $ 1 (4, 9) allowing the construction one (two, three) $\sigma $ statistical intervals of $ {m_{\mathrm{ t } }} $. |
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Figure 4-b:
The statistical uncertainty distribution obtained from pseudo-experiments is compared to the uncertainty of the measurement in data. |
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Figure 5:
Comparison of this result (in red) with previous measurements with lepton+jets final states [45,9,46,36,7] and the CMS [7] and world [47] averages. |
| Tables | |
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Table 1:
List of systematic uncertainties for the fit to the muon+jets data set. |
| Summary |
| The mass of the top quark has been measured with high precision by CMS in Run 1 of the LHC. The most precise of these measurements is repeated using the first data of Run 2 and POWHEG v2 interfaced to PYTHIA 8 with the CUETP8M1 tune for the simulation. Candidate events are selected from $\sqrt{s}= $ 13 TeV data corresponding to an integrated luminosity of 2.2 fb$^{-1}$ requiring one muon and at least four jets with two b tags in the final state. The top quark mass is measured to be 172.62 $\pm$ 0.38 (stat.+JSF) $\pm$ 0.70 (syst.) GeV from the 5798 selected events. This result is consistent with the CMS measurements of Run 1 and no impact from the new reference generator or changes in the experimental setup is observed. This preliminary measurement will serve as a reference for improved measurements of the top quark mass with the Run 2 data. |
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