CMS-PAS-HIG-23-003

CMS-PAS-HIG-23-003
Search for the SM Higgs boson produced in association with bottom quarks in final states with leptons
CMS Collaboration
25 March 2024

Abstract: This note presents the first search for b quark associated production of the Higgs boson, in final states with leptons. Higgs boson decays to pairs of tau leptons and pairs of leptonically decaying W bosons are considered. The search is performed using data collected from 2016 to 2018 by the CMS experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. Upper limits at the 95% confidence level are placed on the signal strength for Higgs boson production in association with b quarks; the observed (expected) upper limit is 3.7 (6.1) times the value expected in the standard model.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PLB. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Dominant Feynman diagrams contributing to Higgs boson production in association with b quarks. The diagrams initiated by gluons (quarks) are shown in the upper (lower) row. The red circle is used to mark the Higgs boson coupling to b quarks, the green circle marks the Higgs boson coupling to top quarks, and the blue circle marks the coupling between the Higgs boson and vector bosons. In the ggH diagram (upper left), the additional gluon is radiated from within the quark loop, although it can equivalently radiate from one of the initial state gluons.
png pdf	Figure 2: BDT $ H\rightarrow\tau\tau $ class output score distributions for the $ \mathrm{e}\tau_{h} $ (upper left), $ \mu\tau_{h} $ (upper right) and $ \tau_{h}\tau_{h} $ (lower left) channels; and $ \mathrm{ H\rightarrow WW} $ output score for the $ \mathrm{e}\mu $ channel (lower right). The distributions are shown using 138 fb$ ^{-1} $ of data collected by the CMS experiment. The bbH signal is multiplied by a factor 50 while all other processes are scaled according to a combined fit of all BDT categories for all channels and years used in this analysis. The total uncertainty includes the statistical and systematic uncertainties. Electroweak processes in the figure include diboson, W+jets, and single top production. For channels involving $ \tau_\mathrm{h} $ candidates the $ \text{jet}\rightarrow\tau_\mathrm{h} $ fakes have been estimated from data and grouped together; they are removed from the the electroweak, $ \text{DY+jets} $, and $ \mathrm{t} \overline{\mathrm{t}} $ groups. The H(125) group includes processes where a Higgs boson is produced not in association with b-quarks.
png	Figure 2-a: BDT $ H\rightarrow\tau\tau $ class output score distributions for the $ \mathrm{e}\tau_{h} $ (upper left), $ \mu\tau_{h} $ (upper right) and $ \tau_{h}\tau_{h} $ (lower left) channels; and $ \mathrm{ H\rightarrow WW} $ output score for the $ \mathrm{e}\mu $ channel (lower right). The distributions are shown using 138 fb$ ^{-1} $ of data collected by the CMS experiment. The bbH signal is multiplied by a factor 50 while all other processes are scaled according to a combined fit of all BDT categories for all channels and years used in this analysis. The total uncertainty includes the statistical and systematic uncertainties. Electroweak processes in the figure include diboson, W+jets, and single top production. For channels involving $ \tau_\mathrm{h} $ candidates the $ \text{jet}\rightarrow\tau_\mathrm{h} $ fakes have been estimated from data and grouped together; they are removed from the the electroweak, $ \text{DY+jets} $, and $ \mathrm{t} \overline{\mathrm{t}} $ groups. The H(125) group includes processes where a Higgs boson is produced not in association with b-quarks.
png	Figure 2-b: BDT $ H\rightarrow\tau\tau $ class output score distributions for the $ \mathrm{e}\tau_{h} $ (upper left), $ \mu\tau_{h} $ (upper right) and $ \tau_{h}\tau_{h} $ (lower left) channels; and $ \mathrm{ H\rightarrow WW} $ output score for the $ \mathrm{e}\mu $ channel (lower right). The distributions are shown using 138 fb$ ^{-1} $ of data collected by the CMS experiment. The bbH signal is multiplied by a factor 50 while all other processes are scaled according to a combined fit of all BDT categories for all channels and years used in this analysis. The total uncertainty includes the statistical and systematic uncertainties. Electroweak processes in the figure include diboson, W+jets, and single top production. For channels involving $ \tau_\mathrm{h} $ candidates the $ \text{jet}\rightarrow\tau_\mathrm{h} $ fakes have been estimated from data and grouped together; they are removed from the the electroweak, $ \text{DY+jets} $, and $ \mathrm{t} \overline{\mathrm{t}} $ groups. The H(125) group includes processes where a Higgs boson is produced not in association with b-quarks.
png	Figure 2-c: BDT $ H\rightarrow\tau\tau $ class output score distributions for the $ \mathrm{e}\tau_{h} $ (upper left), $ \mu\tau_{h} $ (upper right) and $ \tau_{h}\tau_{h} $ (lower left) channels; and $ \mathrm{ H\rightarrow WW} $ output score for the $ \mathrm{e}\mu $ channel (lower right). The distributions are shown using 138 fb$ ^{-1} $ of data collected by the CMS experiment. The bbH signal is multiplied by a factor 50 while all other processes are scaled according to a combined fit of all BDT categories for all channels and years used in this analysis. The total uncertainty includes the statistical and systematic uncertainties. Electroweak processes in the figure include diboson, W+jets, and single top production. For channels involving $ \tau_\mathrm{h} $ candidates the $ \text{jet}\rightarrow\tau_\mathrm{h} $ fakes have been estimated from data and grouped together; they are removed from the the electroweak, $ \text{DY+jets} $, and $ \mathrm{t} \overline{\mathrm{t}} $ groups. The H(125) group includes processes where a Higgs boson is produced not in association with b-quarks.
png	Figure 2-d: BDT $ H\rightarrow\tau\tau $ class output score distributions for the $ \mathrm{e}\tau_{h} $ (upper left), $ \mu\tau_{h} $ (upper right) and $ \tau_{h}\tau_{h} $ (lower left) channels; and $ \mathrm{ H\rightarrow WW} $ output score for the $ \mathrm{e}\mu $ channel (lower right). The distributions are shown using 138 fb$ ^{-1} $ of data collected by the CMS experiment. The bbH signal is multiplied by a factor 50 while all other processes are scaled according to a combined fit of all BDT categories for all channels and years used in this analysis. The total uncertainty includes the statistical and systematic uncertainties. Electroweak processes in the figure include diboson, W+jets, and single top production. For channels involving $ \tau_\mathrm{h} $ candidates the $ \text{jet}\rightarrow\tau_\mathrm{h} $ fakes have been estimated from data and grouped together; they are removed from the the electroweak, $ \text{DY+jets} $, and $ \mathrm{t} \overline{\mathrm{t}} $ groups. The H(125) group includes processes where a Higgs boson is produced not in association with b-quarks.
png pdf	Figure 3: Upper limits at 95% CL on the signal strength for the the $ pp\rightarrow bbH(y_\mathrm{b},y_\mathrm{t}) $ process. The terms contributing to the estimated relative cross sections are those where the Higgs boson is produced via Yukawa coupling with the top or bottom quarks, accounting also for the interference term. The $ pp\rightarrow Z(\rightarrow \mathrm{b}\mathrm{b})H $ process is treated as a background for this measurement and not included in the limits. The theoretical prediction, shown as a red line placed at 1 corresponds to an estimated cross section of 1.489 pb, the black markers show the observed limits, and the dashed lines with the green and yellow uncertainty bands represent the expected upper limits with their 68% and 95% confidence intervals.
png pdf	Figure 4: Two-dimensional confidence intervals on the $ \kappa_\mathrm{b} $ and $ \kappa_\mathrm{t} $ parameters for the channels studied in this search. Expected limits are shown in red for the $ H\rightarrow\tau\tau $ cross section measurement [53] performed on other production mechanisms and in green for the combination with the presented analysis. The observed limits on data are shown in blue, with a cross marking the best-fit point. A green diamond is placed to mark the SM expectation. Solid lines with shaded areas mark the 68% CL contours, while dashed lines mark the 95% CL ones.

Tables
png pdf	Table 1: Summary of the BDT categories defined for each channel
png pdf	Table 2: Input features to the BDT classifiers used in the studied channels. Each variable is marked with the $ \checkmark $ symbol if it is used for the training of the BDT models in a particular channel or the $ \times $ symbol if it is not used.
png pdf	Table 3: Summary table of the systematic uncertainties affecting the background processes. For uncertainties that vary significantly depending on the kinematic properties of the event, the label \textitevent-dep. is used. The labels lnN and shape are used respectively for uncertainties acting only on the normalization or having a shape altering effects.
png pdf	Table 4: Expected and observed upper limits at 95% CL on the signal strength modifier.

Summary

A search for a Higgs boson produced in association with bottom quarks and decaying into a pair of $ \tau $ leptons or W bosons has been presented. The search was performed on data collected by the CMS experiment in the period 2016--2018 at a centre-of-mass energy of $ \sqrt{s}= $ 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. This search has been performed in four final states: $ \mathrm{e}\mu $, $ \mu\tau_{h} $, $ \mathrm{e}\tau_{h} $, and $ \tau_{h}\tau_{h} $. Higgs boson decays to $ \tau $ leptons were targeted in all four final states, while $ \mathrm{ H\rightarrow WW } $ decays contributed only in the $ \mathrm{e}\mu $ channel. At the current level of precision, the background processes provide an adequate description of the observed data, and no significant excess above the background-only expectation was found. The observed (expected) upper limit on the bbH production cross section is found to be 3.7 times (6.1 times) the standard model (SM) prediction at 95% confidence level (CL). The search also constrains the Higgs Yukawa couplings to bottom and top quarks in the $ \kappa $-model interpretation and yields a best-fit value for the couplings of $ (\kappa_t,\kappa_b)=(-0.73,1.58) $. The observed constraints are compatible with the SM expectation at 95% CL.

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