TOP-13-005 (ATLAS-CONF-2013-102): Combination of ATLAS and CMS results on the mass of the top quark using up to 4.9 fb-1 of data

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  • Public PAS: linked here

This result supersedes the previous LHC combined measurement (TOP-12-001). Unlike TOP-12-001, all of the measurements included here use the full 2011 data set. The three CMS measurements are all published. The two ATLAS measurements are still preliminary.

Abstract

A combination of top-quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The dataset used corresponds to an integrated luminosity per experiment of up to 4.9 /fb of proton-proton collisions at a center-of-mass energy of 7 TeV. The combination includes measurements in the the lepton+jets, di-lepton and all-jets channels. The resulting combined LHC measurement of the top-quark mass is 173.29 +/- 0.23 (stat.) +/- 0.92 (syst.) GeV, with a total uncertainty of 0.95 GeV.

Results

  • 5-measurement combination: ATLAS (lepton+jets, di-lepton), CMS (lepton+jets, di-lepton, all-jets)

mass = 173.29 +/- 0.23 (stat.) +/- 0.92 (syst.) GeV

or separating out the iJES statistical contribution from the quoted systematic uncertainty:

mass = 173.29 +/- 0.23 (stat.) +/- 0.26 (iJES) +/- 0.88 (syst.) GeV

Chisq = 1.8 / 4 dof, Probability = 77 %

Figures

Figure Caption
TopMassSummary.png Figure 1a - summary of input mass measurements and the combined result. The LHC combination with the separeted iJES uncertainty is shown in blue and compared to the latest Tevatron result, which is shown in red. [Get pdf version]
TopMassSummary_weights_sep.png Figure 1b - linear combination coefficients calculated using the BLUE method. [Get pdf version]
TopMassSummary_pull_sep.png Figure 1c - pulls for each of the input measurements. [Get pdf version]
Measurement_Correlation_Matrix.png Total correlation matrix for the five input ATLAS and CMS measurements. The elements in the matrix are labelled according to the analysis they correspond to (rows and columns read as ATLAS or CMS collowed by the decay channel name. [Get pdf version]
Plot_corr_dep_updJuly2013_cf_mtop.png Figure 2a - variation of the combined top mass result as a function of the assumed systematic correlation coefficient. For the systematics with a 100% nominal correlation, this is varied from 0 to 100% in steps of 10%. The blue curve is the result of varying all of the ATLAS:CMS (rho_LHC) and internal expt. (rho_exp) simulataneously. The orange (red) curves are the result of varying rho_LHC (rho_exp) only, while the other set of correlations are kept at the nominal value. [Get pdf version]
Plot_corr_dep_updJuly2013_cf_unc.png Figure 2b - variation of the uncertainty on the top mass as a function of the assumed correlation coefficient for the terms which are nominally 100% correlated. The blue, orange and red curves are computed simulataneously with those shown in Fig. 2a. [Get pdf version]
Plot_StabChecks_updJuly2013_mtop.png Figure 2c - variation of the combined top mass result as a function of the assumed value of rho_LHC for selected uncertainty sources. These correspond to the ranges recommended by the TOPLHC working group. Also shown are the effects of investigations of different models for the parton hadronization uncertainty. [Get pdf version]
Plot_StabChecks_updJuly2013_unc.png Figure 2d - variation of the uncertainty on the combined top mass result as a function of the assumed value of rho_LHC for selected uncertainty sources. These correspond to the ranges recommended by the TOPLHC working group. Also shown are the effects of investigations of different models for the parton hadronization uncertainty. [Get pdf version]

Tables

Table Caption
Table_1.png Table 1 - Uncertainty category mapping for the input measurements and the result of the LHC combination. For comparison, the categorization used in the Tevatron 2013 combination is reported in the 1st column. The correlation rho_exp represents the assumed correlation between measurements from the same experiment, while rho_LHC indicates the assumed correlation between measurements across experiments. [Get pdf version]
Table_2.png Table 2 - Evaluation of the impact of the input measurements in the combination. The following values are listed for each measurement, i: the BLUE combination coefficient, the intrinsic information weight IIWi, and the marginal information weight MIWi. The intrinsic information weight IIWcorr of the correllations is also shown on a separate row. [Get pdf version]
Table_3.png Table 3 - Combination results in terms of the three physical parameters corresponding to the masses from each of the individual decay channels. The determination of the mass per decay channel is reported together with the pair-wise correlation coefficients, an the compatibility tests in terms of chisquare/ndf and its associated probability. [Get pdf version]
Table_4.png Table 4 - Combination results in terms of the two physical parameters corresponding to the masses from each of experiments.The determination of the mass per experiment is reported together with the pair-wise correlation coefficients, an the compatibility tests in terms of chisquare/ndf and its associated probability. For comparison, the results of the separate combinations of the individual ATLAS and CMS inputs from Table 1 are reported in the second column. [Get pdf version]
Table_5.png Table 5 - Summary of the combinations performed with nominal and modified correlations applying the recipes of Valessi and Chierici. [Get pdf version]
Table_7.png Table 7 - Results of the individual ATLAS and CMS combinations using the inputs from Table 1. The uncertainty breakdown is provided and compared with the results of the LHC combination. [Get pdf version]

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf Measurement_Correlation_Matrix.pdf r1 manage 295.6 K 2013-09-16 - 20:14 StephenWimpenny Measurement Correlation Matrix
PNGpng Measurement_Correlation_Matrix.png r1 manage 74.5 K 2013-09-16 - 20:20 StephenWimpenny Measurement Correlation Matrix
PDFpdf Plot_StabChecks_updJuly2013_mtop.pdf r1 manage 14.5 K 2013-09-14 - 01:19 StephenWimpenny Stability study (ATLAS:CMS correlations) Top mass - Figure 2c
PNGpng Plot_StabChecks_updJuly2013_mtop.png r1 manage 42.0 K 2013-09-15 - 04:05 StephenWimpenny Stability study (ATLAS:CMS correlations) Top mass - Figure 2c
PDFpdf Plot_StabChecks_updJuly2013_unc.pdf r1 manage 14.6 K 2013-09-14 - 01:20 StephenWimpenny Stability study (ATLAS:CMS correlations) Top mass uncertainty - Figure 2d
PNGpng Plot_StabChecks_updJuly2013_unc.png r1 manage 41.9 K 2013-09-15 - 04:06 StephenWimpenny Stability study (ATLAS:CMS correlations) Top mass uncertainty - Figure 2d
PDFpdf Plot_corr_dep_updJuly2013_cf_mtop.pdf r1 manage 15.2 K 2013-09-14 - 01:17 StephenWimpenny Stability study (correlation coefficients) Top mass - Figure 2a
PNGpng Plot_corr_dep_updJuly2013_cf_mtop.png r1 manage 37.5 K 2013-09-15 - 04:06 StephenWimpenny Stability study (correlation coefficients) Top mass - Figure 2a
PDFpdf Plot_corr_dep_updJuly2013_cf_unc.pdf r1 manage 15.2 K 2013-09-14 - 01:17 StephenWimpenny Stability study (correlation coefficients) Top mass uncertainty - Figure 2b
PNGpng Plot_corr_dep_updJuly2013_cf_unc.png r1 manage 40.3 K 2013-09-15 - 04:07 StephenWimpenny Stability study (correlation coefficients) Top mass uncertainty - Figure 2b
PDFpdf Table_1.pdf r1 manage 1834.7 K 2013-09-27 - 22:07 StephenWimpenny Table 1 - Input Measutrements
PNGpng Table_1.png r1 manage 429.2 K 2013-09-27 - 22:13 StephenWimpenny Table 1 - Input Measutrements
PDFpdf Table_2.pdf r1 manage 310.7 K 2013-09-16 - 19:32 StephenWimpenny Table 2 - BLUEFIN weights
PNGpng Table_2.png r1 manage 75.6 K 2013-09-16 - 19:33 StephenWimpenny Table 2 - BLUEFIN weights
PDFpdf Table_3.pdf r1 manage 290.9 K 2013-09-16 - 19:34 StephenWimpenny Table 3 - Channel-dependent masses
PNGpng Table_3.png r1 manage 67.3 K 2013-09-16 - 19:34 StephenWimpenny Table 3 - Channel-dependent masses
PDFpdf Table_4.pdf r1 manage 225.6 K 2013-09-16 - 19:34 StephenWimpenny Table 4 - CMS and ATLAS masses
PNGpng Table_4.png r1 manage 53.4 K 2013-09-16 - 19:34 StephenWimpenny Table 4 - CMS and ATLAS masses
PDFpdf Table_5.pdf r1 manage 206.6 K 2013-09-16 - 19:35 StephenWimpenny Table 5 - Alternative Fisher minimizations
PNGpng Table_5.png r1 manage 46.9 K 2013-09-16 - 19:35 StephenWimpenny Table 5 - Alternative Fisher minimizations
PDFpdf Table_7.pdf r1 manage 831.2 K 2013-09-16 - 19:36 StephenWimpenny Table 7 - Individual CMS and ATLAS mass combinations (Appendix B)
PNGpng Table_7.png r1 manage 209.0 K 2013-09-16 - 19:36 StephenWimpenny Table 7 - Individual CMS and ATLAS mass combinations (Appendix B)
PDFpdf TopMassSummary.pdf r1 manage 14.9 K 2013-09-14 - 01:12 StephenWimpenny Mass Summary - Figure 1a
PNGpng TopMassSummary.png r1 manage 32.5 K 2013-09-15 - 04:03 StephenWimpenny Mass Summary - Figure 1a
PDFpdf TopMassSummary_pull_sep.pdf r1 manage 13.3 K 2013-09-14 - 01:15 StephenWimpenny Fit pulls - Figure 1c
PNGpng TopMassSummary_pull_sep.png r1 manage 33.9 K 2013-09-15 - 04:04 StephenWimpenny Fit pulls - Figure 1c
PDFpdf TopMassSummary_weights_sep.pdf r1 manage 13.3 K 2013-09-14 - 01:14 StephenWimpenny Blue combination coefficients -Figure 1b
PNGpng TopMassSummary_weights_sep.png r1 manage 36.4 K 2013-09-15 - 04:04 StephenWimpenny Blue combination coefficients -Figure 1b
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Topic revision: r10 - 2014-03-26 - AndreasMeyer
 
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