CMS-PAS-TOP-17-013 | ||
Measurement of jet substructure observables in $\mathrm{t \bar t}$ events from pp collisions at $\sqrt{s}= $ 13 TeV | ||
CMS Collaboration | ||
March 2018 | ||
Abstract: A measurement of differential jet substructure observables is presented using $\mathrm{t \bar t}$ lepton+jets events from proton-proton collisions at $\sqrt{s}= $ 13 TeV recorded by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Multiple jet substructure variables, such as the particle multiplicity, width, eccentricity, $p_\mathrm{T}$ dispersion, N-subjettiness ratios, generalized angularities, and energy correlation functions, are measured for inclusive jets, as well as for identified bottom, light-quark, and gluon jets from the $\mathrm{t \bar t}$ final state. The results are unfolded to the stable-particle level and compared to predictions from POWHEG interfaced with PYTHIA 8 and HERWIG 7.1, as well as from SHERPA 2 and DIRE. A reasonable agreement between the data and the Monte Carlo predictions is found. From a comparison of the jet width distribution to the prediction, it is shown that a lower value of the effective strong coupling in the PYTHIA 8 final-state parton shower is preferred. | ||
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These preliminary results are superseded in this paper, PRD 98 (2018) 092014. The superseded preliminary plots can be found here. |
Figures | |
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Figure 1:
Transverse momentum distribution at the particle level, for inclusive jets (upper left), bottom jets (upper right), light-quark enriched jets (lower left), and gluon-enriched jets (lower right). The bottom panels show the corresponding ratios of the different MC predictions over POWHEG+PYTHIA 8. |
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Figure 1-a:
Transverse momentum distribution at the particle level, for inclusive jets (upper left), bottom jets (upper right), light-quark enriched jets (lower left), and gluon-enriched jets (lower right). The bottom panels show the corresponding ratios of the different MC predictions over POWHEG+PYTHIA 8. |
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Figure 1-b:
Transverse momentum distribution at the particle level, for inclusive jets (upper left), bottom jets (upper right), light-quark enriched jets (lower left), and gluon-enriched jets (lower right). The bottom panels show the corresponding ratios of the different MC predictions over POWHEG+PYTHIA 8. |
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Figure 1-c:
Transverse momentum distribution at the particle level, for inclusive jets (upper left), bottom jets (upper right), light-quark enriched jets (lower left), and gluon-enriched jets (lower right). The bottom panels show the corresponding ratios of the different MC predictions over POWHEG+PYTHIA 8. |
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Figure 1-d:
Transverse momentum distribution at the particle level, for inclusive jets (upper left), bottom jets (upper right), light-quark enriched jets (lower left), and gluon-enriched jets (lower right). The bottom panels show the corresponding ratios of the different MC predictions over POWHEG+PYTHIA 8. |
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Figure 2:
Charged particle multiplicity at the reconstructed level (left) and normalized and unfolded to the particle level (right), in inclusive jets measured in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. The reconstruction-level plot shows the sum of the expected contributions from each process (stacked histograms) compared to the data points (upper panel), and the ratio of the MC prediction (POWHEG+PYTHIA 8) to the data (lower panel), where the dashed band represents the uncertainty on the prediction affecting either the shape or both the shape and normalization of the distribution. The particle-level plot shows the normalized differential cross section (upper panel), and the ratio of multiple MC predictions to data (lower panel) where the grey band indicates the total uncertainty and the hatched black area the statistical uncertainty. |
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Figure 2-a:
Charged particle multiplicity at the reconstructed level (left) and normalized and unfolded to the particle level (right), in inclusive jets measured in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. The reconstruction-level plot shows the sum of the expected contributions from each process (stacked histograms) compared to the data points (upper panel), and the ratio of the MC prediction (POWHEG+PYTHIA 8) to the data (lower panel), where the dashed band represents the uncertainty on the prediction affecting either the shape or both the shape and normalization of the distribution. The particle-level plot shows the normalized differential cross section (upper panel), and the ratio of multiple MC predictions to data (lower panel) where the grey band indicates the total uncertainty and the hatched black area the statistical uncertainty. |
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Figure 2-b:
Charged particle multiplicity at the reconstructed level (left) and normalized and unfolded to the particle level (right), in inclusive jets measured in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. The reconstruction-level plot shows the sum of the expected contributions from each process (stacked histograms) compared to the data points (upper panel), and the ratio of the MC prediction (POWHEG+PYTHIA 8) to the data (lower panel), where the dashed band represents the uncertainty on the prediction affecting either the shape or both the shape and normalization of the distribution. The particle-level plot shows the normalized differential cross section (upper panel), and the ratio of multiple MC predictions to data (lower panel) where the grey band indicates the total uncertainty and the hatched black area the statistical uncertainty. |
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Figure 3:
Distributions of the scaled $ {p_{\mathrm {T}}} $ dispersion ($\lambda _0^{2*}$, left) and Les Houches angularity ($\lambda _{0.5}^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 3-a:
Distributions of the scaled $ {p_{\mathrm {T}}} $ dispersion ($\lambda _0^{2*}$, left) and Les Houches angularity ($\lambda _{0.5}^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 3-b:
Distributions of the scaled $ {p_{\mathrm {T}}} $ dispersion ($\lambda _0^{2*}$, left) and Les Houches angularity ($\lambda _{0.5}^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 4:
Distributions of the jet width ($\lambda _1^1$, left) and thrust ($\lambda _2^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 4-a:
Distributions of the jet width ($\lambda _1^1$, left) and thrust ($\lambda _2^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 4-b:
Distributions of the jet width ($\lambda _1^1$, left) and thrust ($\lambda _2^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 5:
Distributions of the Les Houches angularity ($\lambda _{0.5}^1$, left) and jet width ($\lambda _1^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged+neutral particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 5-a:
Distributions of the Les Houches angularity ($\lambda _{0.5}^1$, left) and jet width ($\lambda _1^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged+neutral particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 5-b:
Distributions of the Les Houches angularity ($\lambda _{0.5}^1$, left) and jet width ($\lambda _1^1$, right), unfolded to the particle level, for inclusive jets reconstructed with charged+neutral particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 6:
Distributions of the eccentricity $\varepsilon $ (left) and the N-subjettiness ratio $\tau _{21}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 6-a:
Distributions of the eccentricity $\varepsilon $ (left) and the N-subjettiness ratio $\tau _{21}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 6-b:
Distributions of the eccentricity $\varepsilon $ (left) and the N-subjettiness ratio $\tau _{21}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 7:
Distributions of N-subjettiness ratios $\tau _{32}$ (left) and $\tau _{43}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 7-a:
Distributions of N-subjettiness ratios $\tau _{32}$ (left) and $\tau _{43}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 7-b:
Distributions of N-subjettiness ratios $\tau _{32}$ (left) and $\tau _{43}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 8:
Distributions of the groomed momentum fraction $z_g$ (left) and the angle between the groomed subjets $\Delta R_g$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 8-a:
Distributions of the groomed momentum fraction $z_g$ (left) and the angle between the groomed subjets $\Delta R_g$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 8-b:
Distributions of the groomed momentum fraction $z_g$ (left) and the angle between the groomed subjets $\Delta R_g$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 9:
Distribution of the soft drop multiplicity $n_{SD}$, unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 10:
Distributions of energy correlation ratios $C_{1}^{ (0.0)}$ (left) and $C_{1}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 10-a:
Distributions of energy correlation ratios $C_{1}^{ (0.0)}$ (left) and $C_{1}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 10-b:
Distributions of energy correlation ratios $C_{1}^{ (0.0)}$ (left) and $C_{1}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 11:
Distributions of energy correlation ratios $C_{1}^{ (0.0)}$ (left) and $C_{1}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged+neutral particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 11-a:
Distributions of energy correlation ratios $C_{1}^{ (0.0)}$ (left) and $C_{1}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged+neutral particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 11-b:
Distributions of energy correlation ratios $C_{1}^{ (0.0)}$ (left) and $C_{1}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged+neutral particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 12:
Distributions of energy correlation ratios $C_{2}^{ (0.0)}$ (left) and $C_{2}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 12-a:
Distributions of energy correlation ratios $C_{2}^{ (0.0)}$ (left) and $C_{2}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 12-b:
Distributions of energy correlation ratios $C_{2}^{ (0.0)}$ (left) and $C_{2}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 13:
Distributions of energy correlation ratios $C_{3}^{ (0.0)}$ (left) and $C_{3}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 13-a:
Distributions of energy correlation ratios $C_{3}^{ (0.0)}$ (left) and $C_{3}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 13-b:
Distributions of energy correlation ratios $C_{3}^{ (0.0)}$ (left) and $C_{3}^{ (1.0)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 14:
Distributions of the energy correlation ratios $M_{2}^{ (1)}$ (left) and $N_{2}^{ (1)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 14-a:
Distributions of the energy correlation ratios $M_{2}^{ (1)}$ (left) and $N_{2}^{ (1)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 14-b:
Distributions of the energy correlation ratios $M_{2}^{ (1)}$ (left) and $N_{2}^{ (1)}$ (right), unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 15:
Distribution of the energy correlation ratio $N_{3}^{ (1)}$, unfolded to the particle level, for inclusive jets reconstructed with charged particles in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. Data (points) are compared to different MC predictions absolutely (upper), and as MC/data ratios (lower). |
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Figure 16:
Distributions of the charged multiplicity (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion ($\lambda _0^{2*}$) (upper right), Les Houches angularity ($\lambda _{0.5}^1$) (lower left), and the energy correlation ratio $C_{3}^{ (1.0)}$ (lower right), unfolded to the particle level, for jets of different flavors measured in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. |
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Figure 16-a:
Distributions of the charged multiplicity (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion ($\lambda _0^{2*}$) (upper right), Les Houches angularity ($\lambda _{0.5}^1$) (lower left), and the energy correlation ratio $C_{3}^{ (1.0)}$ (lower right), unfolded to the particle level, for jets of different flavors measured in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. |
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Figure 16-b:
Distributions of the charged multiplicity (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion ($\lambda _0^{2*}$) (upper right), Les Houches angularity ($\lambda _{0.5}^1$) (lower left), and the energy correlation ratio $C_{3}^{ (1.0)}$ (lower right), unfolded to the particle level, for jets of different flavors measured in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. |
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Figure 16-c:
Distributions of the charged multiplicity (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion ($\lambda _0^{2*}$) (upper right), Les Houches angularity ($\lambda _{0.5}^1$) (lower left), and the energy correlation ratio $C_{3}^{ (1.0)}$ (lower right), unfolded to the particle level, for jets of different flavors measured in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. |
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Figure 16-d:
Distributions of the charged multiplicity (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion ($\lambda _0^{2*}$) (upper right), Les Houches angularity ($\lambda _{0.5}^1$) (lower left), and the energy correlation ratio $C_{3}^{ (1.0)}$ (lower right), unfolded to the particle level, for jets of different flavors measured in $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events at $\sqrt {s} = $ 13 TeV. |
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Figure 17:
Correlations of the jet-shapes observables used in this analysis obtained at particle level based on the full matrix (left), and of four (FSR-sensitive) observables with low correlation (right). |
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Figure 17-a:
Correlations of the jet-shapes observables used in this analysis obtained at particle level based on the full matrix (left), and of four (FSR-sensitive) observables with low correlation (right). |
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Figure 17-b:
Correlations of the jet-shapes observables used in this analysis obtained at particle level based on the full matrix (left), and of four (FSR-sensitive) observables with low correlation (right). |
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Figure 18:
Fit of $ {\alpha _{s}^{\text {FSR}}(m_{{\mathrm {Z}}})} $ using the jet width $\lambda _1^1$ (left), and a scan adding three other observables ($\varepsilon $, $z_{g}$, and $\tau _{43}$) lightly correlated with it and with each other (right). |
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Figure 18-a:
Fit of $ {\alpha _{s}^{\text {FSR}}(m_{{\mathrm {Z}}})} $ using the jet width $\lambda _1^1$ (left), and a scan adding three other observables ($\varepsilon $, $z_{g}$, and $\tau _{43}$) lightly correlated with it and with each other (right). |
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Figure 18-b:
Fit of $ {\alpha _{s}^{\text {FSR}}(m_{{\mathrm {Z}}})} $ using the jet width $\lambda _1^1$ (left), and a scan adding three other observables ($\varepsilon $, $z_{g}$, and $\tau _{43}$) lightly correlated with it and with each other (right). |
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Figure 19:
Scans of $ {\alpha _{s}^{\text {FSR}}(m_{{\mathrm {Z}}})} $ using the $\lambda $ and $C_1$ families of jet substructure observables. |
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Figure 19-a:
Scans of $ {\alpha _{s}^{\text {FSR}}(m_{{\mathrm {Z}}})} $ using the $\lambda $ and $C_1$ families of jet substructure observables. |
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Figure 19-b:
Scans of $ {\alpha _{s}^{\text {FSR}}(m_{{\mathrm {Z}}})} $ using the $\lambda $ and $C_1$ families of jet substructure observables. |
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Figure 20:
Systematic uncertainties for the jet width $\lambda _{1}^1$ (upper left), eccentricity $\varepsilon $ (upper right), groomed momentum fraction $z_{g}$ (lower left), and N-subjettiness ratio $\tau _{43}$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 20-a:
Systematic uncertainties for the jet width $\lambda _{1}^1$ (upper left), eccentricity $\varepsilon $ (upper right), groomed momentum fraction $z_{g}$ (lower left), and N-subjettiness ratio $\tau _{43}$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 20-b:
Systematic uncertainties for the jet width $\lambda _{1}^1$ (upper left), eccentricity $\varepsilon $ (upper right), groomed momentum fraction $z_{g}$ (lower left), and N-subjettiness ratio $\tau _{43}$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 20-c:
Systematic uncertainties for the jet width $\lambda _{1}^1$ (upper left), eccentricity $\varepsilon $ (upper right), groomed momentum fraction $z_{g}$ (lower left), and N-subjettiness ratio $\tau _{43}$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 20-d:
Systematic uncertainties for the jet width $\lambda _{1}^1$ (upper left), eccentricity $\varepsilon $ (upper right), groomed momentum fraction $z_{g}$ (lower left), and N-subjettiness ratio $\tau _{43}$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 21:
Systematic uncertainties for charged multiplicity $\lambda _0^{0}$ (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion $\lambda _0^{2*}$ (upper right), Les Houches angularity $\lambda _{0.5}^1$ (lower left), and the jet thrust $\lambda _{1}^1$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 21-a:
Systematic uncertainties for charged multiplicity $\lambda _0^{0}$ (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion $\lambda _0^{2*}$ (upper right), Les Houches angularity $\lambda _{0.5}^1$ (lower left), and the jet thrust $\lambda _{1}^1$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 21-b:
Systematic uncertainties for charged multiplicity $\lambda _0^{0}$ (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion $\lambda _0^{2*}$ (upper right), Les Houches angularity $\lambda _{0.5}^1$ (lower left), and the jet thrust $\lambda _{1}^1$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 21-c:
Systematic uncertainties for charged multiplicity $\lambda _0^{0}$ (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion $\lambda _0^{2*}$ (upper right), Les Houches angularity $\lambda _{0.5}^1$ (lower left), and the jet thrust $\lambda _{1}^1$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
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Figure 21-d:
Systematic uncertainties for charged multiplicity $\lambda _0^{0}$ (upper left), scaled $ {p_{\mathrm {T}}} $ dispersion $\lambda _0^{2*}$ (upper right), Les Houches angularity $\lambda _{0.5}^1$ (lower left), and the jet thrust $\lambda _{1}^1$ (lower right), compared to the full effect of FSR variations on the particle-level distributions. |
Tables | |
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Table 1:
$\chi ^{2}$ values for the data-MC comparison of the distributions of the four lightly-correlated jet substructure observables, $\lambda _{1}^{1}$, $\varepsilon $, $z_{g}$, and $\tau _{43}$. |
Summary |
A measurement of jet substructure observables in $ \mathrm{t\bar{t}} $ events from pp collisions at 13 TeV is presented, including several variables relevant for quark-gluon discrimination and heavy boosted object identification. The investigated observables are probes for the perturbative and non-perturbative phases of jet evolution, and their unfolded distributions have been derived for inclusive jets, as well as for samples enriched in jets originating from bottom quarks, light quarks, or gluons. The correlations between all jet substructure variables have been studied. Eliminating observables with a high level of correlation, a set of four variables is identified and used for quantifying the level of data-simulation agreement. Data are compared to theoretical predictions either based on NLO matrix-element calculations (POWHEG) interfaced with different generators for the parton shower and hadronization (either PYTHIA 8 or HERWIG 7), or based on SHERPA 2 with NLO corrections, as well as on the DIRE shower. Using the default tunes none of the predictions yields a good overall agreement. Thus, some further tuning of the models is required. For the POWHEG+PYTHIA 8 prediction, a better accord is achieved by lowering the default value of its (effective) strong coupling for final-state radiation, as confirmed by a one-parameter tuning to the jet width $\lambda_{1}^{1}$ yielding a value ${\alpha_{s}^{\text{FSR}}(m_{\mathrm{Z}})} = $ 0.1227 $\pm$ 0.0013. Besides tuning and improving final-state parton showers, the present data can also be compared against modern QCD analytical calculations for infrared and/or collinear-safe observables that include higher fixed-order corrections as well as logarithmic resummations. |
References | ||||
1 | A. Buckley et al. | General-purpose event generators for LHC physics | Phys. Rep. 504 (2011) 145 | 1101.2599 |
2 | ALEPH Collaboration | Studies of QCD at $ e^+e^- $ centre-of-mass energies between 91 GeV and 209 GeV | EPJC 35 (2004) 457 | |
3 | DELPHI Collaboration | Tuning and test of fragmentation models based on identified particles and precision event shape data | Z. Phys. C 73 (1996) 11 | |
4 | DELPHI Collaboration | A study of the b-quark fragmentation function with the DELPHI detector at LEP I and an averaged distribution obtained at the Z pole | EPJC 71 (2011) 1557 | 1102.4748 |
5 | L3 Collaboration | Studies of hadronic event structure in $ e^{+} e^{-} $ annihilation from 30 GeV to 209 GeV with the L3 detector | Phys. Rep. 399 (2004) 71 | hep-ex/0406049 |
6 | OPAL Collaboration | Measurement of event shape distributions and moments in e+ e- $ \to $ hadrons at 91 GeV - 209 GeV and a determination of $ \alpha_s $ | EPJC 40 (2005) 287 | hep-ex/0503051 |
7 | OPAL Collaboration | Measurements of flavor dependent fragmentation functions in Z$ ^0\to q \bar{q} $ events | EPJC 7 (1999) 369 | hep-ex/9807004 |
8 | SLD Collaboration | Production of $ \pi^+, K^+, K^0, K^{* 0}, \phi, p $ and $ {\lambda}bda^0 $ in hadronic Z$ ^0 $ decays | PRD 59 (1999) 052001 | hep-ex/9805029 |
9 | SLD Collaboration | Measurement of the b quark fragmentation function in Z$ ^0 $ decays | PRD 65 (2002) 092006 | hep-ex/0202031 |
10 | C. Frye, A. J. Larkoski, J. Thaler, and K. Zhou | Casimir Meets Poisson: Improved Quark/Gluon Discrimination with Counting Observables | JHEP 09 (2017) 083 | 1704.06266 |
11 | S. D. Ellis, C. K. Vermilion, and J. R. Walsh | Techniques for improved heavy particle searches with jet substructure | PRD 80 (2009) 051501 | 0903.5081 |
12 | A. Altheimer et al. | Boosted objects and jet substructure at the LHC. Report of BOOST2012, held at IFIC Valencia, 23rd-27th of July 2012 | EPJC 74 (2014) 2792 | 1311.2708 |
13 | D. d'Enterria and P. Z. Skands, eds. | Parton Radiation and Fragmentation from LHC to FCC-ee | 1702.01329 | |
14 | A. J. Larkoski, I. Moult, and B. Nachman | Jet Substructure at the Large Hadron Collider: A Review of Recent Advances in Theory and Machine Learning | 1709.04464 | |
15 | S. Marzani, L. Schunk, and G. Soyez | A study of jet mass distributions with grooming | JHEP 07 (2017) 132 | 1704.02210 |
16 | C. Frye, A. J. Larkoski, M. D. Schwartz, and K. Yan | Factorization for groomed jet substructure beyond the next-to-leading logarithm | JHEP 07 (2016) 064 | 1603.09338 |
17 | ATLAS Collaboration | Study of Jet Shapes in Inclusive Jet Production in $ pp $ Collisions at $ \sqrt{s}= $ 7 TeV using the ATLAS Detector | PRD 83 (2011) 052003 | 1101.0070 |
18 | ATLAS Collaboration | ATLAS Measurements of the Properties of Jets for Boosted Particle Searches | PRD 86 (2012) 072006 | 1206.5369 |
19 | CMS Collaboration | Studies of jet mass in dijet and W/Z + jet events | JHEP 05 (2013) 090 | CMS-SMP-12-019 1303.4811 |
20 | ATLAS Collaboration | A measurement of the soft-drop jet mass in pp collisions at $ \sqrt{s} = $ 13 TeV with the ATLAS detector | Submitted to PRLett | 1711.08341 |
21 | ATLAS Collaboration | Measurement of jet shapes in top-quark pair events at $ \sqrt{s} = $ 7 TeV using the ATLAS detector | EPJC 73 (2013) 2676 | 1307.5749 |
22 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
23 | P. Nason | A New method for combining NLO QCD with shower Monte Carlo algorithms | JHEP 11 (2004) 040 | 0409146 |
24 | S. Frixione, P. Nason, and C. Oleari | Matching NLO QCD computations with Parton Shower simulations: the POWHEG method | JHEP 11 (2007) 070 | 0709.2092 |
25 | S. Alioli, P. Nason, C. Oleari, and E. Re | A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX | JHEP 06 (2010) 043 | 1002.2581 |
26 | S. Frixione, P. Nason, and G. Ridolfi | A Positive-weight next-to-leading-order Monte Carlo for heavy flavour hadroproduction | JHEP 09 (2007) 126 | 0707.3088 |
27 | M. Czakon and A. Mitov | Top++: A program for the calculation of the top-pair cross-section at hadron colliders | CPC 185 (2014) 2930 | |
28 | J. Alwall et al. | The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations | JHEP 07 (2014) 079 | 1405.0301 |
29 | R. Frederix and S. Frixione | Merging meets matching in MC@NLO | JHEP 12 (2012) 061 | 1209.6215 |
30 | J. Alwall et al. | Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions | EPJC 53 (2008) 473 | 0706.2569 |
31 | T. Melia, P. Nason, R. Rontsch, and G. Zanderighi | W$ ^+ $W$ ^- $, WZ and ZZ production in the POWHEG BOX | JHEP 11 (2011) 078 | 1107.5051 |
32 | E. Re | Single-top Wt-channel production matched with parton showers using the POWHEG method | EPJC 71 (2011) 1547 | 1009.2450 |
33 | S. Alioli, P. Nason, C. Oleari, and E. Re | NLO single-top production matched with shower in POWHEG: s- and t-channel contributions | JHEP 09 (2009) 111 | 0907.4076 |
34 | S. Frixione, E. Laenen, P. Motylinski, and B. R. Webber | Angular correlations of lepton pairs from vector boson and top quark decays in Monte Carlo simulations | JHEP 04 (2007) 081 | hep-ph/0702198 |
35 | P. Artoisenet, R. Frederix, O. Mattelaer, and R. Rietkerk | Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations | JHEP 03 (2013) 015 | 1212.3460 |
36 | NNPDF Collaboration | Parton distributions for the LHC Run II | JHEP 04 (2015) 040 | 1410.8849 |
37 | T. Sjostrand et al. | An Introduction to $ PYTHIA 8.2 $ | CPC 191 (2015) 159 | 1410.3012 |
38 | E. Norrbin and T. Sjostrand | QCD radiation off heavy particles | NPB 603 (2001) 297 | hep-ph/0010012 |
39 | B. Andersson, G. Gustafson, G. Ingelman, and T. Sjostrand | Parton Fragmentation and String Dynamics | Phys. Rep. 97 (1983) 31 | |
40 | T. Sjostrand | Jet Fragmentation of Nearby Partons | NPB 248 (1984) 469 | |
41 | M. G. Bowler | e+ e- Production of Heavy Quarks in the String Model | Z. Phys. C 11 (1981) 169 | |
42 | CMS Collaboration | Investigations of the impact of the parton shower tuning in $ PYTHIA 8 $ in the modelling of $ \mathrm{t\overline{t}} $ at $ \sqrt{s}= $ 8 and 13 TeV | CMS-PAS-TOP-16-021 | CMS-PAS-TOP-16-021 |
43 | CMS Collaboration | Event generator tunes obtained from underlying event and multiparton scattering measurements | EPJC 76 (2016) 155 | CMS-GEN-14-001 1512.00815 |
44 | M. Bahr et al. | $ HERWIG++ $ Physics and Manual | EPJC 58 (2008) 639 | 0803.0883 |
45 | S. Gieseke, P. Stephens, and B. Webber | New formalism for QCD parton showers | JHEP 12 (2003) 045 | hep-ph/0310083 |
46 | B. R. Webber | A QCD Model for Jet Fragmentation Including Soft Gluon Interference | NPB 238 (1984) 492 | |
47 | GEANT4 Collaboration | GEANT4: A simulation toolkit | NIMA506 (2003) 250 | |
48 | J. Bellm et al. | $ HERWIG $ 7.0/$ HERWIG++ $ 3.0 release note | EPJC 76 (2016) 196 | 1512.01178 |
49 | T. Gleisberg et al. | Event generation with SHERPA 1.1 | JHEP 02 (2009) 007 | 0811.4622 |
50 | S. Frixione and B. R. Webber | Matching NLO QCD computations and parton shower simulations | JHEP 06 (2002) 029 | hep-ph/0204244 |
51 | S. Hoche and S. Prestel | The midpoint between dipole and parton showers | EPJC 75 (2015) 461 | 1506.05057 |
52 | S. Hoche and S. Prestel | Triple collinear emissions in parton showers | PRD 96 (2017) 074017 | 1705.00742 |
53 | S. Hoche, F. Krauss, and S. Prestel | Implementing NLO DGLAP evolution in Parton Showers | JHEP 10 (2017) 093 | 1705.00982 |
54 | S. Schumann and F. Krauss | A Parton shower algorithm based on Catani-Seymour dipole factorisation | JHEP 03 (2008) 038 | 0709.1027 |
55 | J.-C. Winter, F. Krauss, and G. Soff | A Modified cluster hadronization model | EPJC 36 (2004) 381 | hep-ph/0311085 |
56 | T. Sjostrand and M. van Zijl | A Multiple Interaction Model for the Event Structure in Hadron Collisions | PRD 36 (1987) 2019 | |
57 | J. M. Butterworth, J. R. Forshaw, and M. H. Seymour | Multiparton interactions in photoproduction at HERA | Z. Phys. C 72 (1996) 637 | hep-ph/9601371 |
58 | I. Borozan and M. H. Seymour | An Eikonal model for multiparticle production in hadron hadron interactions | JHEP 09 (2002) 015 | hep-ph/0207283 |
59 | M. Bahr, S. Gieseke, and M. H. Seymour | Simulation of multiple partonic interactions in $ HERWIG++ $ | JHEP 07 (2008) 076 | 0803.3633 |
60 | S. Gieseke, C. Rohr, and A. Siodmok | Colour reconnections in $ HERWIG++ $ | EPJC 72 (2012) 2225 | 1206.0041 |
61 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | JINST 12 (2017) P10003 | CMS-PRF-14-001 1706.04965 |
62 | M. Cacciari, G. P. Salam, and G. Soyez | The Anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
63 | M. Cacciari, G. P. Salam, and G. Soyez | FastJet user manual | EPJC 72 (2012) 1896 | 1111.6097 |
64 | CMS Collaboration | Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV | JINST 12 (2017) P02014 | CMS-JME-13-004 1607.03663 |
65 | CMS Collaboration | Identification of b-quark jets with the CMS experiment | JINST 8 (2013) P04013 | CMS-BTV-12-001 1211.4462 |
66 | CMS Collaboration | Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV | Submitted to JINST | CMS-BTV-16-002 1712.07158 |
67 | A. Buckley et al. | Rivet user manual | 1003.0694 |
Compact Muon Solenoid LHC, CERN |