CMS-PAS-HIG-17-007 | ||

Search for the standard model Higgs boson in the dilepton plus photon channel in pp collisions at $\sqrt{s}= $ 13 TeV | ||

CMS Collaboration | ||

March 2018 | ||

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Abstract:
A search for a Higgs boson decaying into a pair of electrons or muons plus a photon is described. This final state has contributions from Higgs decays to a $\mathrm{Z}$ boson and a photon ($\mathrm{H}\rightarrow \mathrm{Z}\gamma\rightarrow \ell\ell\gamma, \ell=\mathrm{e}$ or $\mu$), or to two photons, one of which has an internal conversion into a lepton pair ($\mathrm{H}\rightarrow \gamma^{*}\gamma\rightarrow\mu\mu\gamma$). The analysis is performed using a dataset recorded by the CMS experiment at the LHC from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No significant excess above the background prediction has been found in the 120-130 GeV mass range. Limits are set on the cross section for a standard model Higgs boson decaying to opposite-sign electron or muon pairs and a photon. The observed limits on cross section times the corresponding branching fractions fluctuate between 4 and 1.4 (11 and 6) times the standard model cross section for $\mathrm{H}\rightarrow \gamma^{*}\gamma\rightarrow\mu\mu\gamma$ ($\mathrm{H}\to\mathrm{Z}\gamma\to\ell\ell\gamma$). The $\mathrm{H}\to\gamma^*\gamma\to\mu\mu\gamma$ and $\mathrm{H}\to\mathrm{Z}\gamma\to\ell\ell\gamma$ analyses are combined for $m_\mathrm{H}= $ 125 GeV, obtaining an observed (expected) 95% upper limit of 3.9 (2.0) times the standard model cross section.
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 11 (2018) 152.The superseded preliminary plots can be found here. |

Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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Figures | |

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Figure 1:
Dominant diagrams contributing to $ {\mathrm {H}} \to \ell \ell \gamma $ process. |

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Figure 1-a:
A dominant diagram contributing to $ {\mathrm {H}} \to \ell \ell \gamma $ process. |

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Figure 1-b:
A dominant diagram contributing to $ {\mathrm {H}} \to \ell \ell \gamma $ process. |

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Figure 1-c:
A dominant diagram contributing to $ {\mathrm {H}} \to \ell \ell \gamma $ process. |

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Figure 1-d:
A dominant diagram contributing to $ {\mathrm {H}} \to \ell \ell \gamma $ process. |

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Figure 1-e:
A dominant diagram contributing to $ {\mathrm {H}} \to \ell \ell \gamma $ process. |

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Figure 1-f:
A dominant diagram contributing to $ {\mathrm {H}} \to \ell \ell \gamma $ process. |

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Figure 1-g:
A dominant diagram contributing to $ {\mathrm {H}} \to \ell \ell \gamma $ process. |

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Figure 2:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for all event classes for the $ {\mathrm {H}} \to \gamma ^*\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 2-a:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for the EB, High R9 event class for the $ {\mathrm {H}} \to \gamma ^*\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 2-b:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for the EB, Low R9 event class for the $ {\mathrm {H}} \to \gamma ^*\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 2-c:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for the EE event class for the $ {\mathrm {H}} \to \gamma ^*\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 2-d:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for the Dijet Tagged event class for the $ {\mathrm {H}} \to \gamma ^*\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 3:
Background model fit to the $m_{{\mathrm {e}} {\mathrm {e}}\gamma}$ distribution for untagged 1 (top left), untagged 2 (top right), untagged 3 (middle left), untagged 4 (middle right), di-jet tagged (bottom left) and boosted tag (bottom right) for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to {\mathrm {e}} {\mathrm {e}}\gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 3-a:
Background model fit to the $m_{{\mathrm {e}} {\mathrm {e}}\gamma}$ distribution for untagged 1 for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to {\mathrm {e}} {\mathrm {e}}\gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 3-b:
Background model fit to the $m_{{\mathrm {e}} {\mathrm {e}}\gamma}$ distribution for untagged 2 for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to {\mathrm {e}} {\mathrm {e}}\gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 3-c:
Background model fit to the $m_{{\mathrm {e}} {\mathrm {e}}\gamma}$ distribution for untagged 3 for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to {\mathrm {e}} {\mathrm {e}}\gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 3-d:
Background model fit to the $m_{{\mathrm {e}} {\mathrm {e}}\gamma}$ distribution for untagged 4 for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to {\mathrm {e}} {\mathrm {e}}\gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 3-e:
Background model fit to the $m_{{\mathrm {e}} {\mathrm {e}}\gamma}$ distribution for di-jet tag for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to {\mathrm {e}} {\mathrm {e}}\gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 3-f:
Background model fit to the $m_{{\mathrm {e}} {\mathrm {e}}\gamma}$ distribution for boosted tag for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to {\mathrm {e}} {\mathrm {e}}\gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 4:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for untagged 1 (top left), untagged 2 (top right), untagged 3 (middle left), untagged 4 (middle right), di-jet tagged (bottom left) and boosted tag (bottom right) for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

png pdf |
Figure 4-a:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for untagged 1 tag for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 4-b:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for untagged 2 tag for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

png pdf |
Figure 4-c:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for untagged 3 tag for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

png pdf |
Figure 4-d:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for untagged 4 tag for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

png pdf |
Figure 4-e:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for di-jet tagged tag for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

png pdf |
Figure 4-f:
Background model fit to the $m_{\mu \mu \gamma}$ distribution for di-jet boosted tag for the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \mu \mu \gamma $ selection. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 5:
Background model fit to the $m_{\ell \ell \gamma}$ distribution for $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \ell \ell \gamma $ lepton tag category. The green and yellow bands represent the 68% and 95% uncertainties in the fit to the data. |

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Figure 6:
Exclusion limit, at 95% confidence level, on the cross section of $ {\mathrm {H}} \to \gamma ^*\gamma \to \mu \mu \gamma $ as a function of the Higgs boson mass based on 35.9 fb$^{-1}$ of data taken at 13 TeV. |

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Figure 7:
Exclusion limit, at 95% confidence level, on the cross section of $ {\mathrm {H}} \rightarrow Z\gamma \rightarrow \ell \ell \gamma $ as a function of the Higgs boson mass based on 35.9 fb$^{-1}$ of data taken at 13 TeV. |

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Figure 8:
Exclusion limit, at 95% confidence level, on the cross section of $ {\mathrm {H}} \rightarrow \ell \ell \gamma $ for a SM Higgs boson of $m_ {\mathrm {H}} = $ 125 GeV. The upper limits of each analysis category, as well as their combinations, are shown. Black full (empty) circles show the observed (expected) limit. Red circles show the expected upper limit assuming a SM Higgs boson decaying to $\ell \ell \gamma $ decay channel. |

Tables | |

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Table 1:
Categories in $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \ell \ell \gamma $. |

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Table 2:
Expected signal yields for a 125 GeV SM Higgs boson for all the categories in $ {\mathrm {H}} \to \gamma ^*\gamma \to \mu \mu \gamma $ and $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \ell \ell \gamma $, in the narrowest mass window around 125 GeV containing 68.3% of the expected signal distribution. |

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Table 3:
Fit function chosen as a result of the bias study used in the analysis. |

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Table 4:
Sources of systematic uncertainties considered in the $ {\mathrm {H}} \to {\mathrm {Z}}\gamma \to \ell \ell \gamma $ and $ {\mathrm {H}} \to \gamma ^*\gamma \to \mu \mu \gamma $ analyses. The pre-fit values of the nuisance parameters are shown averaged over all the categories in the analysis in the second column which either affect the normalization of the simulated signal event yields or the mean and resolution of $m_{\ell \ell \gamma}$. |

Summary |

A search has been performed for a SM Higgs boson decaying into a dilepton and a photon. The analysis uses a dataset from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No significant excess has been found and the limits on the Higgs production cross section times the corresponding branching fractions at the LHC have been derived. The expected exclusion limits at 95% confidence level are around 2.3-2.1 (9-3) times the SM cross section in the $\mathrm{H}\to\gamma^*\gamma\to\mu\mu\gamma$ ($\mathrm{H}\to\mathrm{Z}\gamma\to\ell\ell\gamma$) channel in the mass range from 120 and 130 GeV, and the observed limit fluctuates between about 4 and 1.4 (11 and 6) times the SM cross section. Finally, the $\mathrm{H}\to\gamma^*\gamma\to\mu\mu\gamma$ and $\mathrm{H}\to\mathrm{Z}\gamma\to\ell\ell\gamma$ analyses have been combined for $m_\mathrm{H} = $ 125 GeV, obtaining an observed (expected) 95% upper limit of 3.9 (2.0) times the standard model cross section. |

Additional Figures | |

png pdf |
Additional Figure 1:
Final selection efficiency of the signal for $\mathrm{H} \rightarrow \gamma ^{*}\gamma \rightarrow \mu \mu \gamma $ for a $m_{\mathrm{H}}$ range from 120 GeV to 130 GeV. The error band is the $1-\sigma $ systematics uncertainty on the signal efficiency. This uncertainty includes uncertainty on lepton and photon identification scale factors (SFs), HLT SFs, pile-up reweighting and underlying event/parton shower. |

png pdf |
Additional Figure 2:
Final selection efficiency of the signal for $\mathrm{H} \rightarrow \mathrm{Z} \gamma \rightarrow \mathrm{e} \mathrm{e} \gamma $ for a $m_{\mathrm{H}}$ range from 120 GeV to 130 GeV. The error band is the $1-\sigma $ systematics uncertainty on the signal efficiency. This uncertainty includes uncertainty on lepton and photon identification scale factors (SFs), HLT SFs, pile-up reweighting and underlying event/parton shower. |

png pdf |
Additional Figure 3:
Final selection efficiency of the signal for $\mathrm{H} \rightarrow \mathrm{Z} \gamma \rightarrow \mu \mu \gamma $ for a $m_{\mathrm{H}}$ range from 120 GeV to 130 GeV. The error band is the $1-\sigma $ systematics uncertainty on the signal efficiency. This uncertainty includes uncertainty on lepton and photon identification scale factors (SFs), HLT SFs, pile-up reweighting and underlying event/parton shower. |

png pdf |
Additional Figure 4:
Combined p-value of the analyses, $\mathrm{H} \to \gamma ^*\gamma \to \mu \mu \gamma $ and $\mathrm{H} \to \mathrm{Z} \gamma \to \ell \ell \gamma $. The expected with signal injected at $m_{\mathrm{H}} = $ 125 GeV is shown in dotted red line. The black line shows the observed. |

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Compact Muon Solenoid LHC, CERN |