Projections for measurements of Higgs boson cross sections, branching ratios and coupling parameters with the ATLAS detector at a HL-LHC

ATL-PHYS-PUB-2013-014

6 October 2013

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Abstract
Studies are presented on the prospects for measuring Higgs boson production cross sections times branching ratios, and determining couplings to individual fermions and bosons in 14 TeV proton-proton collisions at the LHC with 300 fb$^{-1}$ and at the HL-LHC with 3000 fb$^{-1}$. Several studies already presented at the 2012 European Strategy meeting are updated. In addition first analyses are presented of $H \rightarrow Z\gamma$, of $ZH$ production with $H\rightarrow$ invisible final states, and on the measurement of the Higgs width from the interference in $H \rightarrow \gamma \gamma$.
Figures
Figure 01a:
The distribution of the number of b-tagged jets (a) and the number of additional leptons in events with at least one b-tagged (b), for different Higgs production mechanisms and ZZ background.

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Figure 01b:
The distribution of the number of b-tagged jets (a) and the number of additional leptons in events with at least one b-tagged (b), for different Higgs production mechanisms and ZZ background.

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Figure 02a:
The distribution of Δη (a) and the mass mjj (b) of the selected dijet pair, for different Higgs production mechanisms and background.

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Figure 02b:
The distribution of Δη (a) and the mass mjj (b) of the selected dijet pair, for different Higgs production mechanisms and background.

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Figure 03a:
Invariant mass distribution of the 4-lepton system for the ttH-like (a), VH-like (b), VBF-like (c) and ggF-like categories (d).

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Figure 03b:
Invariant mass distribution of the 4-lepton system for the ttH-like (a), VH-like (b), VBF-like (c) and ggF-like categories (d).

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Figure 03c:
Invariant mass distribution of the 4-lepton system for the ttH-like (a), VH-like (b), VBF-like (c) and ggF-like categories (d).

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Figure 03d:
Invariant mass distribution of the 4-lepton system for the ttH-like (a), VH-like (b), VBF-like (c) and ggF-like categories (d).

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Figure 04:
The expected diphoton mass distribution for the inclusive category. The blue line shows the fitted background distribution. The lower plot shows the signal distribution, fitted to the simulated signal events and pseudo-data background distribution, after subtracting the fitted background.

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Figure 05a:
Distribution of Δη and mjj in the 2-jet/VBF category.

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Figure 05b:
Distribution of Δη and mjj in the 2-jet/VBF category.

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Figure 06a:
Diphoton mass spectrum for signal and both reducible and irreducible backgrounds after parametrised photon reconstruction in the 0-jet (a) 1-jet (b) and 2-jet/VBF (c) categories.

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Figure 06b:
Diphoton mass spectrum for signal and both reducible and irreducible backgrounds after parametrised photon reconstruction in the 0-jet (a) 1-jet (b) and 2-jet/VBF (c) categories.

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Figure 06c:
Diphoton mass spectrum for signal and both reducible and irreducible backgrounds after parametrised photon reconstruction in the 0-jet (a) 1-jet (b) and 2-jet/VBF (c) categories.

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Figure 07a:
Distributions of mllγ and mllγ-mll for signal(× 20) and background for the inclusive analysis.

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Figure 07b:
Distributions of mllγ and mllγ-mll for signal(× 20) and background for the inclusive analysis.

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Figure 07c:
Distributions of mllγ and mllγ-mll for signal(× 20) and background for the inclusive analysis.

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Figure 07d:
Distributions of mllγ and mllγ-mll for signal(× 20) and background for the inclusive analysis.

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Figure 08:
Distribution of mllγ-mll for signal and background. The lower panel shows the signal after background subtraction for the inclusive analysis, with the expected data uncertainties.

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Figure 09a:
Distribution of Δη, Δφ and the mass of two jets present in the event.

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Figure 09b:
Distribution of Δη, Δφ and the mass of two jets present in the event.

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Figure 09c:
Distribution of Δη, Δφ and the mass of two jets present in the event.

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Figure 10a:
The real component of the interference (a) is odd around the Higgs boson mass, with a sharp spike but long tails. Smearing this shape with the experimental resolution broadens observed cross section (b), and adding this to the nominal signal model (c) leads to a shift in the apparent mass. The interference and signal line shapes were provided by Dixon and Li, the experimental mγγ resolution corresponds to the Run I resolution.

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Figure 10b:
The real component of the interference (a) is odd around the Higgs boson mass, with a sharp spike but long tails. Smearing this shape with the experimental resolution broadens observed cross section (b), and adding this to the nominal signal model (c) leads to a shift in the apparent mass. The interference and signal line shapes were provided by Dixon and Li, the experimental mγγ resolution corresponds to the Run I resolution.

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Figure 10c:
The real component of the interference (a) is odd around the Higgs boson mass, with a sharp spike but long tails. Smearing this shape with the experimental resolution broadens observed cross section (b), and adding this to the nominal signal model (c) leads to a shift in the apparent mass. The interference and signal line shapes were provided by Dixon and Li, the experimental mγγ resolution corresponds to the Run I resolution.

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Figure 11a:
The mass distributions for the low- and high-pTH regions for 1 × ΓSM and 200 × ΓSM after background subtraction are illustrated: the data points correspond to a randomized sample of 3000 fb-1, the green dashed line corresponds to the BW without any interference, the magenta line shows the interference correction, and the solid yellow line the summed signal and interference contribution. The red curve is a fit with a Gaussian signal PDF to illustrate the apparent mass shift.

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Figure 11b:
The mass distributions for the low- and high-pTH regions for 1 × ΓSM and 200 × ΓSM after background subtraction are illustrated: the data points correspond to a randomized sample of 3000 fb-1, the green dashed line corresponds to the BW without any interference, the magenta line shows the interference correction, and the solid yellow line the summed signal and interference contribution. The red curve is a fit with a Gaussian signal PDF to illustrate the apparent mass shift.

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Figure 11c:
The mass distributions for the low- and high-pTH regions for 1 × ΓSM and 200 × ΓSM after background subtraction are illustrated: the data points correspond to a randomized sample of 3000 fb-1, the green dashed line corresponds to the BW without any interference, the magenta line shows the interference correction, and the solid yellow line the summed signal and interference contribution. The red curve is a fit with a Gaussian signal PDF to illustrate the apparent mass shift.

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Figure 11d:
The mass distributions for the low- and high-pTH regions for 1 × ΓSM and 200 × ΓSM after background subtraction are illustrated: the data points correspond to a randomized sample of 3000 fb-1, the green dashed line corresponds to the BW without any interference, the magenta line shows the interference correction, and the solid yellow line the summed signal and interference contribution. The red curve is a fit with a Gaussian signal PDF to illustrate the apparent mass shift.

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Figure 12a:
Projected 95% upper limits on the Higgs boson width, at 300 fb-1 and 3000 fb-1. The dashed red line depicts the expected shift between the low- and high-pT samples as a function of the true width. The black dashed line at Δ mH = -54.4 MeV is the expected shift for the SM width. The light/dark shaded region denotes allowed 95% one-sided Neyman confidence belt determined via Asimov data sets taking into account statistical (light) or statistical and systematic (dark) uncertainties. The intercepts between the SM value and the blue curves are the expected upper limits on the width, assuming a SM Higgs boson.

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Figure 12b:
Projected 95% upper limits on the Higgs boson width, at 300 fb-1 and 3000 fb-1. The dashed red line depicts the expected shift between the low- and high-pT samples as a function of the true width. The black dashed line at Δ mH = -54.4 MeV is the expected shift for the SM width. The light/dark shaded region denotes allowed 95% one-sided Neyman confidence belt determined via Asimov data sets taking into account statistical (light) or statistical and systematic (dark) uncertainties. The intercepts between the SM value and the blue curves are the expected upper limits on the width, assuming a SM Higgs boson.

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Figure 13:
The m T distributions after all the selection cuts, but before the final m T window cut, in the N jet = 0 (left) and N jet = 1 (right) final states for μp=50 with 300 fb-1 of total integrated luminosity.

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Figure 14:
The m T distributions after all the selection cuts, but before the final m T window cut, in the N jet = 0 (left) and N jet = 1 (right) final states for μp=140 with 3000 fb-1 of total integrated luminosity.

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Figure 15a:
The m T distribution after all the selection cuts, but before the final m T cut, in the N jet >= 2 final state for μp=50 with 300 fb-1 of total integrated luminosity (left) and μp=140 with 3000 fb-1 of total integrated luminosity (right) .

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Figure 15b:
The m T distribution after all the selection cuts, but before the final m T cut, in the N jet >= 2 final state for μp=50 with 300 fb-1 of total integrated luminosity (left) and μp=140 with 3000 fb-1 of total integrated luminosity (right) .

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Figure 16a:
(a) Distribution of the μmu invariant mass of the signal and background processes generated for √s=14 TeV and L=3000 fb-1. (b) Background subtracted invariant mass distribution of a toy MC sample generated under the signal-plus-background hypothesis for L=3000 fb-1.

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Figure 16b:
(a) Distribution of the μmu invariant mass of the signal and background processes generated for √s=14 TeV and L=3000 fb-1. (b) Background subtracted invariant mass distribution of a toy MC sample generated under the signal-plus-background hypothesis for L=3000 fb-1.

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Figure 17:
The invariant mass of the di-muon system in the tt H, H to μμ channel.

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Figure 18a:
ETmiss distributions for 300 and 3000 fb-1 14 TeV data samples.

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Figure 18b:
ETmiss distributions for 300 and 3000 fb-1 14 TeV data samples.

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Figure 19a:
Upper limits (90% CL) on the dark matter-nucleon scattering cross section in Higgs-portal scenarios, extracted from the expected Higgs to invisible branching fraction limit and from direct-search experiments. The results are shown for three spin scenarios of the DM candidate: a scalar, vector or fermion particle. The hatched areas correspond to the uncertainty of the nucleon form factor.

Revised May 13, 2014: this figure has been updated to correct an error in the calculation of the ATLAS upper limits on the dark matter-nucleon scattering cross section in the Higgs-portal model. The result from CDMS II has also been updated to the latest one.


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Figure 19b:
Upper limits (90% CL) on the dark matter-nucleon scattering cross section in Higgs-portal scenarios, extracted from the expected Higgs to invisible branching fraction limit and from direct-search experiments. The results are shown for three spin scenarios of the DM candidate: a scalar, vector or fermion particle. The hatched areas correspond to the uncertainty of the nucleon form factor.

Revised May 13, 2014: this figure has been updated to correct an error in the calculation of the ATLAS upper limits on the dark matter-nucleon scattering cross section in the Higgs-portal model. The result from CDMS II has also been updated to the latest one.


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Figure 20a:
Limits on the Higgs-dark matter couplings in Higgs-portal scenarios, extracted from the expected Higgs to invisible branching fraction limit. The results are shown for three spin scenarios of the DM candidate: a scalar, vector or fermion particle.

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Figure 20b:
Limits on the Higgs-dark matter couplings in Higgs-portal scenarios, extracted from the expected Higgs to invisible branching fraction limit. The results are shown for three spin scenarios of the DM candidate: a scalar, vector or fermion particle.

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Figure 21a:
Relative uncertainty on the total signal strength μ for all Higgs final states in the different experimental categories used in the combination, assuming a SM Higgs Boson with a mass of 125 GeV and LHC at 14 TeV, 300 fb-1 and 3000 fb-1. The hashed areas indicate the increase of the estimated error due to current theory systematic uncertainties. The abbreviation ``(comb.)'' indicates that the precision on μ is obtained from the combination of the measurements from the different experimental sub-categories for the same final state, while ``(incl.)'' indicates that the measurement from the inclusive analysis was used. The left side shows only the combined signal strength in the considered final states, while the right side also shows the signal strength in the main experimental sub-categories within each final state.

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Figure 21b:
Relative uncertainty on the total signal strength μ for all Higgs final states in the different experimental categories used in the combination, assuming a SM Higgs Boson with a mass of 125 GeV and LHC at 14 TeV, 300 fb-1 and 3000 fb-1. The hashed areas indicate the increase of the estimated error due to current theory systematic uncertainties. The abbreviation ``(comb.)'' indicates that the precision on μ is obtained from the combination of the measurements from the different experimental sub-categories for the same final state, while ``(incl.)'' indicates that the measurement from the inclusive analysis was used. The left side shows only the combined signal strength in the considered final states, while the right side also shows the signal strength in the main experimental sub-categories within each final state.

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Figure 22a:
68% and 95% CL likelihood contours for κV and κF in a minimal coupling fit at 14 TeV for an assumed integrated luminosity of 300 fb-1 (Left) and for 3000 fb-1 (Right).

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Figure 22b:
68% and 95% CL likelihood contours for κV and κF in a minimal coupling fit at 14 TeV for an assumed integrated luminosity of 300 fb-1 (Left) and for 3000 fb-1 (Right).

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Figure 23:
Relative uncertainty on the expected precision for the determination of coupling scale factor ratios uplambdaXY in a generic fit without assumptions, assuming a SM Higgs Boson with a mass of 125 GeV and LHC at 14 TeV, 300 fb-1 and 3000 fb-1. The hashed areas indicate the increase of the estimated error due to current theory systematics uncertainties. The numerical values can be found in model Nr. 5 in Table 19.

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Figure 24:
Fit results for mass-scaled coupling ratios Yfγfγ(mf/v) for fermions and YVγVγ(mV/v) for weak bosons as a function of the particle mass, assuming 300 fb-1 and 3000 fb-1 at 14 TeV and a SM Higgs Boson with a mass of 125 GeV. For completeness, the uncertainty on the gluon-coupling ratio measurement κgγ, which can be used as an indirect measurement of the top-coupling through the gg to H process, is also shown next to the expected measurement for Ytγ which uses the direct ttH process. The uncertainty on the coupling ratio κ(Zγ)γ is not shown. The relative uncertainties on the ratios can be found in model Nr. 6 in Table 19.

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2024-03-19 01:28:23