CMS-PAS-TOP-22-001; ATLAS-CONF-2023-066; CERN-LPCC-2023-02

CMS-PAS-TOP-22-001; ATLAS-CONF-2023-066; CERN-LPCC-2023-02
Combination of measurements of the top quark mass from data collected by the ATLAS and CMS experiments at $\sqrt{s}=$ 7 and 8 TeV
CMS Collaboration
26 September 2023

Abstract: A combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The data sets used correspond to an integrated luminosity of up to 5 and 20 fb $^{-1}$ of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top-quark pair events that exploit both the semi-leptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak $t$ -channel. The combination yields $m_{\mathrm{t}} =$ 172.52 $\pm$ 0.14 (stat) $\pm$ 0.30 (syst) GeV, with a total uncertainty of 0.33 GeV.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ; These preliminary results are superseded in this paper, Accepted by PRL. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Comparison of the individual $m_{\mathrm{t}}$ measurements and the result of the overall LHC Run 1 $m_{\mathrm{t}}$ combination. Also shown are the separate combinations of each experiment and the result of the simultaneous combination for the different decay channels, where the ``other" category covers the single-top, $\mathrm{J}/\psi$ and secondary vertex measurements.
png pdf	Figure A1: Simultaneous extraction of the top quark mass measured by ATLAS ( $m_{\mathrm{t}}^\text{ATLAS}$ ) and CMS ( $m_{\mathrm{t}}^\text{CMS}$ ) from a BLUE combination of the 15 input measurements. The solid ellipses show the 68% and 95% confidence intervals of the combination and are in good agreement with the expectation $m_{\mathrm{t}}^\text{ATLAS}=m_{\mathrm{t}}^\text{CMS}$ (shown by the black dashed line). The observed correlation between $m_{\mathrm{t}}^\text{ATLAS}$ and $m_{\mathrm{t}}^\text{CMS}$ is 0.15. The blue and red lines and bands show the central values and 68% confidence intervals for the individual ATLAS and CMS combinations, which use the 6 ATLAS and 9 CMS measurements respectively. The central value of the LHC combination, $m_{\mathrm{t}}^\text{LHC}$ , which assumes $m_{\mathrm{t}}^\text{LHC}=m_{\mathrm{t}}^\text{ATLAS}=m_{\mathrm{t}}^\text{CMS}$ , is shown by the full marker. The projection of the diagonal error bar on any of the axes represents the total uncertainty $m_{\mathrm{t}}^\text{LHC}$ .
png pdf	Figure A2: Correlation matrix for the ATLAS and CMS $m_{\mathrm{t}}$ measurements.

Tables
png pdf	Table 1: Correlation strengths $\rho$ of the systematic uncertainty categories between ATLAS and CMS, as used in the combination. Categories indicated with the symbol $\text{---}$ \ in the second column correspond to uncertainties specific to a single experiment. The third column shows the range of $\rho$ scanned for stability checks. The corresponding changes in the central value $m_{\mathrm{t}}$ and uncertainty $\sigma_{m_{\mathrm{t}}}$ of the combination are shown in the last two columns.
png pdf	Table 2: Impact of the uncertainty categories in the LHC, ATLAS, and CMS combinations.
png pdf	Table A1: BLUE weights of the simultaneous ATLAS and CMS combination. The sum of the ATLAS weights in the CMS combined value is zero, and vice versa. The individual weights, however, are different from zero due to the correlation between the different experiments
png pdf	Table A2: Results and systematic uncertainties of the ATLAS $m_{\mathrm{t}}$ measurements, shown separately for the 7 and 8 TeV results in the dilepton (``dil''), lepton+jets (``lj''), and all-jets (``aj'') channels, and for their combination (``comb.''). All values are given in GeVns.
png pdf	Table A3: Results and systematic uncertainties of the CMS $m_{\mathrm{t}}$ measurements, shown separately for the 7 and 8 TeV results in the dilepton (``dil''), lepton+jets (``lj''), and all-jets (``aj'') channels, for the 8 TeV results in the single top (``t''), secondary vertex (``vtx''), and $\mathrm{J}/\psi$ analysis (`` $\mathrm{J}/\psi$ ''), and for their combination (``comb.''). All values are given in GeVns.
png pdf	Table A4: Pulls and weights of each input measurement in the LHC combination.
png pdf	Table A5: Weights for each input measurement for the simultaneous combination of the four different channels. The CMS alternative measurements are assigned to the ``other'' channel.
png pdf	Table B1: Correlation matrix for LHC JES 1
png pdf	Table B2: Correlation matrix for LHC JES 2
png pdf	Table B3: Correlation matrix for LHC JES 3
png pdf	Table B4: Correlation matrix for LHC b-JES
png pdf	Table B5: Correlation matrix for LHC g-JES
png pdf	Table B6: Correlation matrix for LHC l-JES
png pdf	Table B7: Correlation matrix for CMS JES 1
png pdf	Table B8: Correlation matrix for JER
png pdf	Table B9: Correlation matrix for Leptons
png pdf	Table B10: Correlation matrix for b tagging
png pdf	Table B11: Correlation matrix for $p_{\mathrm{T}}^\text{miss}$
png pdf	Table B12: Correlation matrix for Pileup
png pdf	Table B13: Correlation matrix for Trigger
png pdf	Table B14: Correlation matrix for ME generator
png pdf	Table B15: Correlation matrix for LHC radiation
png pdf	Table B16: Correlation matrix for LHC hadronization
png pdf	Table B17: Correlation matrix for CMS ${\mathrm{B}}$ hadron BR
png pdf	Table B18: Correlation matrix for Color reconnection
png pdf	Table B19: Correlation matrix for Underlying event
png pdf	Table B20: Correlation matrix for PDF
png pdf	Table B21: Correlation matrix for Top quark $p_{\mathrm{T}}$
png pdf	Table B22: Correlation matrix for Background (data)
png pdf	Table B23: Correlation matrix for Background (MC)
png pdf	Table B24: Correlation matrix for Method
png pdf	Table B25: Correlation matrix for Other

Summary

In summary, a combination of top quark mass measurements by the ATLAS and CMS experiments at the CERN LHC in pp collisions at

$\sqrt{s}=$ 7 and 8 TeV has been performed. The combination yields

$m_{\mathrm{t}} =$ 172.52

$\pm$ 0.33 GeV, with a precision of 2 per mill.

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