CMS-HIG-13-001 ; CERN-PH-EP-2014-117 | ||
Observation of the diphoton decay of the Higgs boson and measurement of its properties | ||
CMS Collaboration | ||
2 July 2014 | ||
Eur. Phys. J. C 74 (2014) 3076 | ||
Abstract: Observation of the diphoton decay mode of the recently discovered Higgs boson and measurement of some of its properties are reported. The analysis uses the entire dataset collected by the CMS experiment in proton-proton collisions during the 2011 and 2012 LHC running periods. The data samples correspond to integrated luminosities of 5.1 fb$ ^{-1} $ at $ \sqrt{s} $ = 7 TeV and 19.7 fb$ ^{-1} $ at 8 TeV. A clear signal is observed in the diphoton channel at a mass close to 125 GeV with a local significance of 5.7$ \sigma $, where a significance of 5.2$ \sigma $ is expected for the standard model Higgs boson. The mass is measured to be 124.70 $\pm$ 0.34 GeV = 124.70 $\pm$ 0.31 (stat) $\pm$ 0.15 (syst) GeV, and the best-fit signal strength relative to the standard model prediction is 1.14 $ ^{+0.26}_{-0.23} $ =1.14 $\pm$ 0.21 (stat) $ ^{+0.09}_{-0.05}$ (syst) $ ^{+0.13}_{-0.09} $ (theo). Additional measurements include the signal strength modifiers associated with different production mechanisms, and hypothesis tests between spin-0 and spin-2 models. | ||
Links: e-print arXiv:1407.0558 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; Public twiki page ; CADI line (restricted) ; |
Cover | |
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Cover of the European Journal or Physics C, Volume 14, Number 10, published October 2014. |
Figures | |
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Figure 1:
Invariant mass of $\mathrm{ e }^- \mathrm{ e }^+ $ pairs in $ {\mathrm{ Z } \to \mathrm{ e }^- \mathrm{ e }^+ } $ events in the 8 TeV data (points), and in simulated events (histogram), in which the electron showers are reconstructed as photons, and the full set of photon corrections and smearings are applied. The comparison is shown for (left) events with both showers in the barrel, and (right) the remaining events. For each bin, the ratio of the number of events in data to the number of simulated events is shown in the lower main plot. |
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Figure 2:
Photon identification BDT score of the lower-scoring photon of diphoton pairs with an invariant mass in the range 100 $ < {m_{\gamma \gamma }} < $ 180 GeV, for events passing the preselection in the 8 TeV dataset (points), and for simulated background events (histogram with shaded error bands showing the statistical uncertainty). Histograms are also shown for different components of the simulated background, in which there are either two, one, or zero prompt signal-like photons. The tall histogram on the right (righthand vertical axis) corresponds to simulated Higgs boson signal events. |
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Figure 3:
Comparison of the photon identification BDT score for electron showers in the barrel in $ { {\mathrm {Z}}\to {\mathrm {e}^+} {\mathrm {e}^-}} $ events in the 8 TeV dataset and MC simulated events, for events passing the preselection, but with the electron veto condition inverted. The systematic uncertainty assigned to the photon identification BDT score is shown as a band. The comparison is shown for two sets of events with different numbers of primary vertices, $ {N_\mathrm {vtx}} $. For each bin, the ratio of the number of events in data to the number of simulated events is shown in the lower plot. |
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Figure 4:
Fraction of diphoton vertices (solid points) assigned, by the vertex assignment BDT, to a reconstructed vertex within 10 mm of their true location in simulated Higgs boson events, $ {m_ {\mathrm {H}} }$ = 125 GeV , $\sqrt {s}$ = 8 TeV , as a function of $ {p_{\mathrm {T}}^{\gamma \gamma }} $. Also shown is a band, the centre of which is the mean prediction, from the vertex probability BDT, of the probability of correctly locating the vertex. The mean is calculated in ${p_{\mathrm {T}}^{\gamma \gamma }} $ bins, and the width of the band represents the event-to-event uncertainty in the estimates. |
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Figure 5:
Distribution of the vertex probability estimate in $ { {\mathrm {Z}}\to {{\mu ^+}} {{\mu ^-}}} $ events. The vertex probability estimates in 8 TeV data (points), are compared to the estimates in MC simulation (histograms). The comparison is made separately for events in which the vertex is assigned to the same (open circles and filled histogram), or to a different vertex (filled circles and outlined histogram), as that identified by the muons. |
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Figure 6:
Transformed diphoton BDT classifier score for events satisfying the full diphoton preselection in the 8 TeV data (points with error bars, left axis), and for simulated signal events from the four production processes (solid filled histograms, right axis). The outlined histogram, following the data points, is for simulated background events. The vertical dashed lines show the boundaries of the untagged event classes, with the leftmost dashed line representing the score below which events are discarded and not used in the final analysis. |
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Figure 7:
Transformed diphoton BDT classifier score for $ { {\mathrm {Z}}\to {\mathrm {e}^+} {\mathrm {e}^-}} $ events in 8 TeV data, and in MC simulation, in which the electrons are reconstructed as photons. The distribution of simulated events is represented by a histogram, and the data by points with error bars. For each bin, the ratio of the number of events in data to the number of simulated events is shown in the lower plot. The bands in the two plots indicate the systematic uncertainty related to the MC cluster shape uncertainty (see text). The vertical dashed lines show the boundaries of the untagged event classes, with the leftmost dashed line representing the score below which events are discarded and not used in the final analysis. |
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Figure 8:
Score of the combined dijet-diphoton BDT for events satisfying the dijet preselection in 8 TeV data (points with error bars, left axis) and for simulated signal events from the four production processes (histograms, right axis). The outlined histogram is for simulated background events; the shaded error bands on the histogram show the statistical uncertainty in the simulation. The vertical dashed lines show the boundaries of the event classes, with the leftmost dashed line representing the score below which events are not included in the VBF dijet-tagged classes, but remain candidates for inclusion in other classes. The classifier score is transformed such that signal events produced by the VBF process have a uniform, flat, distribution. |
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Figure 9-a:
Events in the four untagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 9-b:
Events in the four untagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 9-c:
Events in the four untagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 9-d:
Events in the four untagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 10-a:
Events in the five untagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 10-b:
Events in the five untagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 10-c:
Events in the five untagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 10-d:
Events in the five untagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 10-e:
Events in the five untagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 11-a:
Events in the two VBF dijet-tagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 11-b:
Events in the two VBF dijet-tagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 12-a:
Events in the three VBF dijet-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 12-b:
Events in the three VBF dijet-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 12-c:
Events in the three VBF dijet-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 13-a:
Events in the VH-tagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 13-b:
Events in the VH-tagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 13-c:
Events in the VH-tagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 13-d:
Events in the VH-tagged classes of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 14-a:
Events in the VH-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit are computed from the fit uncertainty in the background yield in bins corresponding to those used to display the data. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 14-b:
Events in the VH-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit are computed from the fit uncertainty in the background yield in bins corresponding to those used to display the data. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 14-c:
Events in the VH-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit are computed from the fit uncertainty in the background yield in bins corresponding to those used to display the data. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 14-d:
Events in the VH-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit are computed from the fit uncertainty in the background yield in bins corresponding to those used to display the data. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 15:
Events in the $ { {\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {H}} } $-tagged class of the 7 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model for $ {m_ {\mathrm {H}} }$ = 124.7 GeV. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of function and the uncertainty in the fitted parameters. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 16-a:
Events in the two $ { {\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {H}} } $-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit are computed from the fit uncertainty in the background yield in bins corresponding to those used to display the data. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 16-b:
Events in the two $ { {\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {H}} } $-tagged classes of the 8 TeV dataset, binned as a function of $ {m_{\gamma \gamma }} $, together with the result of a fit of the signal-plus-background model. The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit are computed from the fit uncertainty in the background yield in bins corresponding to those used to display the data. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. |
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Figure 17:
Sum of the 25 signal-plus-background model fits to the event classes in both the 7 and 8 TeV datasets, together with the data binned as a function of ${m_{\gamma \gamma }}$ . The $1\sigma $ and $2\sigma $ uncertainty bands shown for the background component of the fit are computed from the fit uncertainty in the background yield in bins corresponding to those used to display the data. These bands do not contain the Poisson uncertainty that must be included when the full uncertainty in the number of background events in any given mass range is estimated. The lower plot shows the residual data after subtracting the fitted background component. |
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Figure 18:
Local $p$-values as a function of $ {m_ {\mathrm {H}} }$ for the 7 TeV, 8 TeV, and the combined dataset. The values of the expected significance, calculated using the background expectation obtained from the signal-plus-background fit, are shown as dashed lines. |
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Figure 19:
Diphoton mass spectrum weighted by the ratio $S/(S+B)$ in each event class, together with the background subtracted weighted mass spectrum. |
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Figure 20-a:
Best-fit signal strength, $ \hat{\mu } $, shown as a function of the mass hypothesis, ${m_ {\mathrm {H}} }$. The results are shown for the standard analysis (a), and for the cut-based cross-check analysis (b). |
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Figure 20-b:
Best-fit signal strength, $ \hat{\mu } $, shown as a function of the mass hypothesis, ${m_ {\mathrm {H}} }$. The results are shown for the standard analysis (a), and for the cut-based cross-check analysis (b). |
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Figure 21:
Values of $ \hat{\mu} $ measured individually for all event classes in the 7 and 8 TeV datasets, fixing $ {m_ {\mathrm {H}} }$ =124.7 GeV. The horizontal bars indicate ${\pm }1\sigma $ uncertainties in the values, and the vertical line and band indicate the best-fit signal strength in the combined fit to the data and its uncertainty. |
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Figure 22-a:
(a) Scan of the likelihood ratio, $q$, as a function of the hypothesised mass when $\mu _{ {\mathrm {g}} {\mathrm {g}} {\mathrm {H}} , { {\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {H}} } }$ and $\mu _\text {VBF, VH}$ are allowed to vary independently. (b) Map of $q( {m_ {\mathrm {H}} },\mu )$ showing the $1\sigma $ and $2\sigma $ regions, and the best-fit point $( \hat{m}_{\mathrm{H}} , \hat{\mu} )$ = (124.70 GeV ,1.14). |
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Figure 22-b:
(a) Scan of the likelihood ratio, $q$, as a function of the hypothesised mass when $\mu _{ {\mathrm {g}} {\mathrm {g}} {\mathrm {H}} , { {\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {H}} } }$ and $\mu _\text {VBF, VH}$ are allowed to vary independently. (b) Map of $q( {m_ {\mathrm {H}} },\mu )$ showing the $1\sigma $ and $2\sigma $ regions, and the best-fit point $( \hat{m}_{\mathrm{H}} , \hat{\mu} )$ = (124.70 GeV ,1.14). |
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Figure 23:
Map of the likelihood ratio $q(\mu _{ {\mathrm {g}} {\mathrm {g}} {\mathrm {H}} , { {\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {H}} } },\mu _\text {VBF, VH})$ with ${m_ {\mathrm {H}} }$ treated as an unconstrained parameter. The $1\sigma $ and $2\sigma $ uncertainty contours are shown. The cross indicates the best-fit values, ($ \hat{\mu} _{ {\mathrm {g}} {\mathrm {g}} {\mathrm {H}} , { {\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {H}} } }, \hat{\mu} _\text {VBF, VH})=(1.13, 1.16)$, and the diamond represents the SM expectation. |
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Figure 24:
Best-fit signal strength, $ \hat{\mu} $, measured for each of the production processes in a combined fit where the signal strengths of all four processes have been allowed to vary independently in the fit. The signal mass, common to all four processes, is treated as an unconstrained parameter in the fit. The horizontal bars indicate ${\pm }1\sigma $ uncertainties in the values for the individual processes. The band corresponds to ${\pm }1\sigma $ uncertainties in the value obtained from the combined fit with a single signal strength. |
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Figure 25-a:
Maps of the likelihood ratio $q( {\kappa _\mathrm {V}} , {\kappa _\mathrm {f}} )$ (a), and $q( {\kappa _{\gamma }} , {\kappa _\mathrm {g}} )$ (b), showing the $1\sigma $ and $2\sigma $ uncertainty contours. The crosses indicate the best-fit values, and the diamonds indicate the SM expectation. |
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Figure 25-b:
Maps of the likelihood ratio $q( {\kappa _\mathrm {V}} , {\kappa _\mathrm {f}} )$ (a), and $q( {\kappa _{\gamma }} , {\kappa _\mathrm {g}} )$ (b), showing the $1\sigma $ and $2\sigma $ uncertainty contours. The crosses indicate the best-fit values, and the diamonds indicate the SM expectation. |
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Figure 26:
Scan of the negative-log-likelihood ratio as a function of the Higgs boson decay width. The observed (expected) upper limit on the width is found to be 2.4 (3.1) GeV at a 95% CL. |
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Figure 27:
Exclusion limit on the signal strength, $ {\sigma \mathrm {'}/\sigma _\mathrm {SM}} $, for a second Higgs-boson-like state with SM couplings taking the observed state at 125 GeV as part of the background. The shading indicates a window with a width of 10 GeV , centred at the best-fit mass, where the expected sensitivity to a second Higgs boson is severely degraded due to the presence of the already observed state. |
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Figure 28-a:
Exclusion limits on $ {\sigma \mathrm {'}/\sigma _\mathrm {SM}} $ for a second Higgs-boson-like state produced with gluon-gluon fusion only (left) or VBF and VH only (right) taking the observed state at 125 GeV as part of the background. The shading indicates a window with a width of 10 GeV, centred at the best-fit mass, where the expected sensitivity to a second Higgs boson is severely degraded due to the presence of the already observed state. |
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Figure 28-b:
Exclusion limits on $ {\sigma \mathrm {'}/\sigma _\mathrm {SM}} $ for a second Higgs-boson-like state produced with gluon-gluon fusion only (left) or VBF and VH only (right) taking the observed state at 125 GeV as part of the background. The shading indicates a window with a width of 10 GeV, centred at the best-fit mass, where the expected sensitivity to a second Higgs boson is severely degraded due to the presence of the already observed state. |
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Figure 29-a:
Map of the values of the likelihood ratio $q(x,\Delta m)$ for two near mass-degenerate states parameterized by $x$ (the fraction of signal in the lower mass state) and $\Delta m$ (the mass difference between the states). The black cross shows the best-fit value, and the lines correspond to the $1\sigma $ and $2\sigma $ uncertainty contours for the SM (single state) expectation (upper plot) and the observation (lower plot). |
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Figure 29-b:
Map of the values of the likelihood ratio $q(x,\Delta m)$ for two near mass-degenerate states parameterized by $x$ (the fraction of signal in the lower mass state) and $\Delta m$ (the mass difference between the states). The black cross shows the best-fit value, and the lines correspond to the $1\sigma $ and $2\sigma $ uncertainty contours for the SM (single state) expectation (upper plot) and the observation (lower plot). |
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Figure 30:
Product of acceptance and efficiency $A\times \epsilon $ for ${0^{+}}$ (all SM production modes), ${2^{+}_{m}}$ (gluon-fusion) and $ {2^{+}_{m}} $ ($ {\mathrm {q}} {\overline {\mathrm {q}}}$ production) as a function of $ | \cos{ \theta^*}_{\mathrm{SC} } | $, as calculated for the 8 TeV dataset. The value of $A\times \epsilon $ for the ${2^{+}_{m}}$ models divided by $A\times \epsilon $ for SM is shown below, where the bands indicate the spread of values among the four diphoton classes. The $ | \cos{ \theta^*}_{\mathrm{SC} }| $ bin boundaries are shown by vertical dashed lines. |
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Figure 31:
Histograms showing signal strength in five bins of $ | \cos{ \theta^*}_{\mathrm{SC} }| $ expected for SM, for $ {2^{+}_{m}} $ produced by $ {\mathrm {g}} {\mathrm {g}}$, and for ${2^{+}_{m}}$ produced by $ {\mathrm {q}} {\overline {\mathrm {q}}}$. The signal strength observed in the data is shown by the black points. |
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Figure 32:
Test statistic for pseudo-experiments generated under the SM, $ {0^{+}} $, hypothesis (open squares) and the graviton-like, ${2^{+}_{m}} $, hypothesis (open diamonds), as a function of the fraction, $ {f_{ {\mathrm {q}} {\overline {\mathrm {q}}}}} $, of $ {\mathrm {q}} {\overline {\mathrm {q}}}$ production. The observed distribution in the data is shown by the black points. |
Tables | |
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Table 1:
Photon preselection efficiencies for both the 7 and 8 TeV datasets measured for $ {\mathrm{ Z } \to \mathrm{ e }^- \mathrm{ e }^+ } $ events, where the electrons are reconstructed as photons, in four photon categories. The statistical uncertainties in the efficiencies found in simulated events are negligible, and the uncertainties measured in data are discussed in the text. |
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Table 2:
Event classes for the 7 and 8 TeV datasets and some of their main selection requirements. Events are tested against the selection requirements of the classes in the order they are listed here. |
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Table 3:
Expected number of SM Higgs boson events ($ {m_\mathrm{ H } }= $ 125 GeV) and estimated background (``Bkg.'') at $ {m_{\gamma \gamma }} = $ 125 GeV for all event classes of the 7 and 8 TeV datasets. The composition of the SM Higgs boson signal in terms of the production processes and its mass resolution is also given. The number corresponding to the production process making the largest contribution to each event class is highlighted in boldface. Numbers are omitted for production processes representing less than 0.05% of the total signal. The variables used to characterize the resolution, $\sigma _\text {eff}$ and $\sigma _\mathrm {HM}$, are defined in the text. |
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Table 4:
Selection requirements for the VBF dijet tag in the cut-based and dijet 2D analyses. The variables are defined in the text. |
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Table 5:
Values of the best-fit signal strength, $ {\hat{\mu }} $, when ${m_\mathrm{ H } }$ is treated as an unconstrained parameter, for the 7 TeV , 8 TeV , and combined datasets. The corresponding best-fit value of $ {m_\mathrm{ H } }$, $ { \hat{m}_\mathrm{ H } } $, is also given. |
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Table 6:
Expected and observed best-fit values of the signal strength for a SM Higgs boson signal in the alternative analyses, together with their uncertainties, indicating the expected uncertainty in the measurement at the best-fit values of $ {m_\mathrm{ H } }$, and the best-fit values obtained from the data. The corresponding values for the main analysis are shown for comparison. |
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Table 7:
Magnitude of the uncertainty in the best fit signal strength, $ {\hat{\mu }} $, induced by the systematic uncertainties in the signal model. To obtain the values, the quadratic subtraction, needed to remove the statistical uncertainty, is made for the positive and negative uncertainties separately. The values quoted are the average magnitudes of the positive and negative uncertainties. The statistical uncertainty includes all uncertainties in the background modelling. |
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Table 8:
Magnitude of the uncertainty in the best fit mass induced by the systematic uncertainties in the signal model. These numbers have been obtained by quadratic subtraction of the statistical uncertainty. The statistical uncertainty includes all uncertainties in the background modelling. |
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Table 9:
Expected and observed best-fit values of the signal strength modifiers $\mu _{ \mathrm{ggH } , \mathrm{ ttH } }$ and $\mu _{\text {VBF, VH}}$ for a SM Higgs boson signal together with their uncertainties, indicating the expected uncertainty in the measurement and the best-fit values obtained from the data. |
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Table 10:
Best-fit signal strength modifiers for the four production processes. The total uncertainty for each process is separated into statistical (stat) and systematic contributions. The systematic uncertainty has been separated, where feasible, into the contributions from theoretical (theo), and experimental (exp) uncertainties. To obtain the values, the quadratic subtraction, needed to remove the statistical uncertainty, is made for the positive and negative uncertainties separately. The values quoted are the average magnitudes of the positive and negative uncertainties. |
png pdf |
Table 11:
Expected and observed values of $1- {\mathrm {CL}_\mathrm {s}} $ for the ${2^{+}_{m}}$ signal hypothesis with respect to the ${0^{+}}$ hypothesis, for different mixtures of $\mathrm{gg} $ and $\mathrm{ q } \mathrm{ \bar{q} } $ production. |
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Compact Muon Solenoid LHC, CERN |