CMS-PAS-HIG-21-015

CMS-PAS-HIG-21-015
Search for the Higgs boson decay to a pair of electrons in proton-proton collisions at $\sqrt{s}= $ 13 TeV
CMS Collaboration
March 2022

Abstract: A search is presented for the Higgs boson decay to a pair of electrons in proton-proton collisions at $\sqrt{s}= $ 13 TeV. The data set was collected with the CMS experiment at the LHC between 2016 and 2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis uses event categories targeting Higgs boson production via gluon-fusion and vector boson fusion. An upper limit on the Higgs boson branching fraction to an electron pair is determined as 3.0$\times$10$^{-4}$ (3.0$\times$10$^{-4}$ expected) at the 95% confidence level. This is the most stringent limit on the Higgs boson branching fraction to a pair of electrons to date.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PLB. The superseded preliminary plots can be found here.

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Output score of the VBF BDT in simulated background and signal events, and data (left). The ggH and VBF signals are scaled such that they are visible. Category boundaries targeting VBF production are denoted with dashed lines. The shaded region defines events which are not selected to enter VBF analysis categories, but may populate those targeting ggH. The right plot shows the distribution of the output score of the VBF BDT in the Z-mass control region. Good agreement is observed between the DY simulation (filled histogram) and the combination of data taken in 2016, 2017, and 2018 (black points), within the phase space in which analysis categories are constructed.
png pdf	Figure 1-a: Output score of the VBF BDT in simulated background and signal events, and data (left). The ggH and VBF signals are scaled such that they are visible. Category boundaries targeting VBF production are denoted with dashed lines. The shaded region defines events which are not selected to enter VBF analysis categories, but may populate those targeting ggH. The right plot shows the distribution of the output score of the VBF BDT in the Z-mass control region. Good agreement is observed between the DY simulation (filled histogram) and the combination of data taken in 2016, 2017, and 2018 (black points), within the phase space in which analysis categories are constructed.
png pdf	Figure 1-b: Output score of the VBF BDT in simulated background and signal events, and data (left). The ggH and VBF signals are scaled such that they are visible. Category boundaries targeting VBF production are denoted with dashed lines. The shaded region defines events which are not selected to enter VBF analysis categories, but may populate those targeting ggH. The right plot shows the distribution of the output score of the VBF BDT in the Z-mass control region. Good agreement is observed between the DY simulation (filled histogram) and the combination of data taken in 2016, 2017, and 2018 (black points), within the phase space in which analysis categories are constructed.
png pdf	Figure 2: Output score of the ggH BDT in simulated background and signal events, and data (left). The ggH and VBF signals are scaled such that they are visible. Category boundaries targeting ggH Higgs boson production are denoted with dashed lines. Events with scores in the grey shaded region are discarded from the analysis. The right plot shows the distribution of the output score of the ggH BDT in a control region around the Z boson mass. The DY simulation (filled histogram) is compared to the combination of data taken in 2016, 2017, and 2018 (black points). The residual differences between data and simulation are smaller than the ggH cross section uncertainty presented in Section 7.
png pdf	Figure 2-a: Output score of the ggH BDT in simulated background and signal events, and data (left). The ggH and VBF signals are scaled such that they are visible. Category boundaries targeting ggH Higgs boson production are denoted with dashed lines. Events with scores in the grey shaded region are discarded from the analysis. The right plot shows the distribution of the output score of the ggH BDT in a control region around the Z boson mass. The DY simulation (filled histogram) is compared to the combination of data taken in 2016, 2017, and 2018 (black points). The residual differences between data and simulation are smaller than the ggH cross section uncertainty presented in Section 7.
png pdf	Figure 2-b: Output score of the ggH BDT in simulated background and signal events, and data (left). The ggH and VBF signals are scaled such that they are visible. Category boundaries targeting ggH Higgs boson production are denoted with dashed lines. Events with scores in the grey shaded region are discarded from the analysis. The right plot shows the distribution of the output score of the ggH BDT in a control region around the Z boson mass. The DY simulation (filled histogram) is compared to the combination of data taken in 2016, 2017, and 2018 (black points). The residual differences between data and simulation are smaller than the ggH cross section uncertainty presented in Section 7.
png pdf	Figure 3: Signal models for the highest S/B categories targeting ggH and VBF processes, integrated over production processes, for Higgs boson events simulated at ${m_\mathrm{H}} =$ 125 GeV. The contribution from each of the three years are shown by the dashed lines. The models are normalised to unit area. The ${\sigma _{\text {eff}}}$ is the smallest interval containing 68% of the ${m_{\mathrm{e} \mathrm{e}}}$ signal distribution.
png pdf	Figure 3-a: Signal models for the highest S/B categories targeting ggH and VBF processes, integrated over production processes, for Higgs boson events simulated at ${m_\mathrm{H}} =$ 125 GeV. The contribution from each of the three years are shown by the dashed lines. The models are normalised to unit area. The ${\sigma _{\text {eff}}}$ is the smallest interval containing 68% of the ${m_{\mathrm{e} \mathrm{e}}}$ signal distribution.
png pdf	Figure 3-b: Signal models for the highest S/B categories targeting ggH and VBF processes, integrated over production processes, for Higgs boson events simulated at ${m_\mathrm{H}} =$ 125 GeV. The contribution from each of the three years are shown by the dashed lines. The models are normalised to unit area. The ${\sigma _{\text {eff}}}$ is the smallest interval containing 68% of the ${m_{\mathrm{e} \mathrm{e}}}$ signal distribution.
png pdf	Figure 4-a: The signal-plus-background model fit to the ${m_{\mathrm{e} \mathrm{e}}}$ distribution for the highest S/B analysis categories targeting ggH (left) and VBF (right) processes. The signal model for each category is also shown, scaled to the observed limit at $ {m_\mathrm{H}} = $ 125.38 GeV. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The lower panel shows the residuals after subtraction of this background component.
png pdf	Figure 4-b: The signal-plus-background model fit to the ${m_{\mathrm{e} \mathrm{e}}}$ distribution for the highest S/B analysis categories targeting ggH (left) and VBF (right) processes. The signal model for each category is also shown, scaled to the observed limit at $ {m_\mathrm{H}} = $ 125.38 GeV. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The lower panel shows the residuals after subtraction of this background component.
png pdf	Figure 5: Expected and observed limits on ${\mathcal {B}({\mathrm {H}\rightarrow {\mathrm {e}^{+}\mathrm {e}^{-}}})}$ for a Higgs boson mass between 120 and 130 GeV.
png pdf	Figure 6: Expected and observed limits on ${\mathcal {B}({\mathrm {H}\rightarrow {\mathrm {e}^{+}\mathrm {e}^{-}}})}$ for for each constructed analysis category, and all categories combined. The results here assume a SM Higgs boson with a mass of 125.38 GeV.

Summary

A search for the Higgs boson decaying into two electrons is performed using proton-proton collision data collected at $\sqrt{s}= $ 13 TeV with the CMS experiment at the LHC between 2016 and 2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis uses categories targeting Higgs boson production via gluon fusion and vector boson fusion, with dedicated boosted decision tree classifiers trained for each production mode to enhance the sensitivity of the resulting categories. A maximum likelihood fit to the dielectron mass distribution is performed simultaneously to each analysis category to extract an upper limit on the Higgs boson to electron pair branching fraction. The resulting observed (expected) limit at the 95% CL on the branching fraction for H $\to$ ee decays is 3.0$\times $10$^{-4}$ (3.0$\times $10$^{-4}$). This is the most stringent limit on the Higgs boson branching fraction to two electrons to date.

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