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| CMS-PAS-TOP-17-004 | ||
| Constraining the top quark Yukawa coupling from $\text{t}\bar{\text{t}}$ differential cross sections in the lepton+jets final state in proton-proton collisions at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| March 2019 | ||
| Abstract: A measurement of the top quark Yukawa coupling from the top quark-antiquark ($\text{t}\bar{\text{t}}$) differential production cross sections in proton-proton collisions with the lepton+jets channel is presented. Corrections due to electroweak bosons exchange, including the Higgs boson, between the final state top quarks can produce large distortions of differential distributions near the energy threshold of top quark pair production. Therefore precise measurements of these distributions are sensitive to the Yukawa coupling. This analysis is based on data collected by the CMS experiment at the LHC at $\sqrt{s}= $ 13 TeV corresponding to an integrated luminosity of 35.8 fb$^{-1}$. Top quark events are reconstructed with at least three jets in the final state. A novel technique is introduced to reconstruct the $\text{t}\bar{\text{t}}$ system for events with one missing jet. This technique enhances the experimental sensitivity in the low invariant mass region, $M_{\text{t}\bar{\text{t}}}$. The data yields in $M_{\text{t}\bar{\text{t}}}$, the rapidity difference $|y_\text{t}-y_{\bar{\text{t}}}|$, and the number of reconstructed jets are compared with distributions representing different Yukawa couplings. These comparisons are used to extract an upper limit on the top quark Yukawa coupling of 1.67 (1.62 expected) at 95% confidence level. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PRD 100 (2019) 072007. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Example diagrams for gluon-induced process of $ {{\mathrm {t}\overline {\mathrm {t}}}} $ production and the virtual corrections. $\Gamma $ stands for all contributions from the gauge boson, Goldstone boson and Higgs boson exchanges. |
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Figure 2:
The dependence of the ratio of EW correction over the leading-order production cross section on the sensitive kinematic variables ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ and ${\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ for different values of Yukawa coupling, as evaluated with HATHOR [5]. The lines contain an uncertainty band derived from the dependence of the EW correction on the top quark mass varied by $\pm $1 GeV. The effect of the top quark mass is very small at the parton level and not visible in the scale of the plot. |
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Figure 2-a:
The dependence of the ratio of EW correction over the leading-order production cross section on the kinematic variable ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ for different values of Yukawa coupling, as evaluated with HATHOR [5]. The lines contain an uncertainty band derived from the dependence of the EW correction on the top quark mass varied by $\pm $1 GeV. The effect of the top quark mass is very small at the parton level and not visible in the scale of the plot. |
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Figure 2-b:
The dependence of the ratio of EW correction over the leading-order production cross section on the kinematic variable ${\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ for different values of Yukawa coupling, as evaluated with HATHOR [5]. The lines contain an uncertainty band derived from the dependence of the EW correction on the top quark mass varied by $\pm $1 GeV. The effect of the top quark mass is very small at the parton level and not visible in the scale of the plot. |
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Figure 3:
Three-jet reconstruction. Upper left: normalized distributions of the distance ${D_{\nu,\mathrm {min}}}$ for correctly and wrongly selected $\mathrm {b}_{\ell}$ candidates. Upper right: normalized mass distribution of the correctly and wrongly selected $\mathrm {b}_h$ and the jet from W. Lower plot: Distribution of the negative combined log-likelihood. |
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Figure 3-a:
Three-jet reconstruction. Normalized distributions of the distance ${D_{\nu,\mathrm {min}}}$ for correctly and wrongly selected $\mathrm {b}_{\ell}$ candidates. |
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Figure 3-b:
Three-jet reconstruction. Normalized mass distribution of the correctly and wrongly selected $\mathrm {b}_h$ and the jet from W. |
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Figure 3-c:
Three-jet reconstruction. Distribution of the negative combined log-likelihood. |
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Figure 4:
Resolution of the invariant mass of the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ system (left) and the difference in rapidity of top quark/antiquark (right) for three-jet and at least four-jet event categories. |
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Figure 4-a:
Resolution of the invariant mass of the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ system for three-jet and at least four-jet event categories. |
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Figure 4-b:
Resolution of the difference in rapidity of top quark/antiquark for three-jet and at least four-jet event categories. |
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Figure 5:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plots show the missing transverse momentum ($ {p_\mathrm {T}^{\mathrm {miss}}}$), the lepton pseudorapidity, and $ {p_{\mathrm {T}}} $ and absolute rapidity $y$ of leptonic top quark, hadronic top quark, and the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ system. The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of each panel. |
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Figure 5-a:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plot shows the missing transverse momentum ($ {p_\mathrm {T}^{\mathrm {miss}}}$). The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of the panel. |
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Figure 5-b:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plot shows the lepton pseudorapidity. The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of the panel. |
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Figure 5-c:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plot shows the $ {p_{\mathrm {T}}} $ of the hadronic top quark. The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of the panel. |
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Figure 5-d:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plot shows the $ {p_{\mathrm {T}}} $ of the leptonic top quark. The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of the panel. |
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Figure 5-e:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plot shows the absolute rapidity $y$ of the hadronic top quark. The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of the panel. |
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Figure 5-f:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plot shows the absolute rapidity $y$ of the leptonic top quark. The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of the panel. |
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Figure 5-g:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plot shows the $ {p_{\mathrm {T}}} $ of the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ system. The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of the panel. |
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Figure 5-h:
Three-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. The plot shows the absolute rapidity $y$ of the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ system. The hatched band shows the total uncertainty associated with signal and background predictions with the sources of uncertainty uncorrelated and summed in quadrature. The ratios of data to the sum of the predicted yields are provided at the bottom of the panel. |
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Figure 6:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same plots as described in Fig. 5. |
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Figure 6-a:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 6-b:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 6-c:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 6-d:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 6-e:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 6-f:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 6-g:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 6-h:
Four-jet events after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 7:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same plots as described in Fig. 5. |
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Figure 7-a:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 7-b:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 7-c:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 7-d:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 7-e:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 7-f:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 7-g:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 7-h:
Events with five or more jets after selection and $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction. Same as corresponding plot in Fig. 5. |
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Figure 8:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. Each plot corresponds to one of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed in each bin. |
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Figure 8-a:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. The plot corresponds to bin 1 of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 8-b:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. The plot corresponds to bin 2 of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 8-c:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. The plot corresponds to bin 3 of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 8-d:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. The plot corresponds to bin 4 of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 8-e:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. The plot corresponds to bin 5 of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 8-f:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. The plot corresponds to bin 6 of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 8-g:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. The plot corresponds to bin 7 of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 8-h:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the three-jet category. The plot corresponds to bin 8 of the eight ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 9:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the categories with four and five or more jets. Each plot corresponds to one of the six ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed in each bin. |
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Figure 9-a:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the categories with four and five or more jets. Each plot corresponds to bin 1 of the six ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 9-b:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the categories with four and five or more jets. Each plot corresponds to bin 2 of the six ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 9-c:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the categories with four and five or more jets. Each plot corresponds to bin 3 of the six ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 9-d:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the categories with four and five or more jets. Each plot corresponds to bin 4 of the six ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 9-e:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the categories with four and five or more jets. Each plot corresponds to bin 5 of the six ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 9-f:
The strength of the EW correction, relative to the POWHEG expected signal, ${R^{\mathrm {bin}}(Y_t)}$, as a function of ${Y_{\text {t}}}$ in the categories with four and five or more jets. Each plot corresponds to bin 6 of the six ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ bins for $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} | < $ 0.6 (see Fig. 10). A quadratic fit is performed. |
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Figure 10:
The $ {M_{{{\mathrm {t}\overline {\mathrm {t}}}}}} $ distribution in $| {\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}} |$ bins for all channels combined, after the likelihood fit. The hatched bands show the total post-fit uncertainty. The ratios of data to the sum of the predicted yields are provided at the bottom of each panel. |
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Figure 11:
The test-statistic scan versus ${Y_{\text {t}}}$ for each channel (three jets, four jets, five or more jets), and all channels combined. The test-statistic minimum indicates the best fit of ${Y_{\text {t}}}$. The horizontal lines indicate 68% CL and 95% CL. |
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Figure 11-a:
The test-statistic scan versus ${Y_{\text {t}}}$ for the three-jets channel. The test-statistic minimum indicates the best fit of ${Y_{\text {t}}}$. The horizontal lines indicate 68% CL and 95% CL. |
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Figure 11-b:
The test-statistic scan versus ${Y_{\text {t}}}$ for the four-jets channel. The test-statistic minimum indicates the best fit of ${Y_{\text {t}}}$. The horizontal lines indicate 68% CL and 95% CL. |
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Figure 11-c:
The test-statistic scan versus ${Y_{\text {t}}}$ for the five-or-more-jets channel. The test-statistic minimum indicates the best fit of ${Y_{\text {t}}}$. The horizontal lines indicate 68% CL and 95% CL. |
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Figure 11-d:
The test-statistic scan versus ${Y_{\text {t}}}$ for all three-jets, four-jets and five-or-more-jets channels combined. The test-statistic minimum indicates the best fit of ${Y_{\text {t}}}$. The horizontal lines indicate 68% CL and 95% CL. |
| Tables | |
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Table 1:
Expected and observed yields with statistical uncertainties after event selection. Events are categorized in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ simulation as: correctly identified $ {{\mathrm {t}\overline {\mathrm {t}}}} $ systems (${{\mathrm {t}\overline {\mathrm {t}}}}$ right); events where all decay products are available, but the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ reconstruction algorithm did not identify the correct $ {{\mathrm {t}\overline {\mathrm {t}}}} $ permutation (${{\mathrm {t}\overline {\mathrm {t}}}}$ wrong); non-reconstructible events where the algorithm failed to identify at least one top candidate (${{\mathrm {t}\overline {\mathrm {t}}}}$ not reco); and events arising from the dileptonic or fully hadronic $ {{\mathrm {t}\overline {\mathrm {t}}}} $ channels (${{\mathrm {t}\overline {\mathrm {t}}}}$ background). |
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Table 2:
Summary of the sources of systematic uncertainties, their effects and magnitudes on signal and backgrounds. If the uncertainty shows a shape dependency on the ${M_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ and ${\Delta y_{{{\mathrm {t}\overline {\mathrm {t}}}}}}$ distributions, it is being considered in the likelihood and labeled as "shape'' in the table. For columns with several numbers, the numbers refer to the events with three, four, five and more jets. |
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Table 3:
The expected and observed 95% CL limits on ${Y_{\text {t}}}$. |
| Summary |
| A limit on the top quark Yukawa coupling is presented, extracted by investigating top lepton+jets decays into a muon or electron and several jets in 35.8 fb$^{-1}$ of CMS data at $\sqrt{s} = $ 13 TeV. The $\mathrm{t\bar{t}}$ production rate is sensitive to the top quark Yukawa coupling through electroweak corrections that can modify the distributions of the mass of top quark-antiquark pairs, $ {M_{\mathrm{t\bar{t}}}} $, and the rapidity difference between top quarks/antiquarks, $\delta Y$. Top quark-antiquark pair events have been reconstructed with a novel algorithm applied to events with three or at least four reconstructed jets and two b tags. The inclusion of events where only three jets are reconstructed (one missing jet in the leading order lepton+jets topology) improves the sensitivity of the analysis by including more events from the low $ {M_{\mathrm{t\bar{t}}}} $ region, which is most sensitive to the Yukawa coupling. The top quark Yukawa coupling is extracted by comparing the data with the expected $\mathrm{t\bar{t}}$ signal for different values of $ {Y_{\text{t}}} $ in a total of 57 bins in $ {M_{\mathrm{t\bar{t}}}} $, $\delta Y$, and the number of reconstructed jets. The value of the top quark Yukawa coupling is constrained to be less than 1.67 at the 95% confidence level. |
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Compact Muon Solenoid LHC, CERN |
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