CMS-PAS-HIG-17-019

CMS-PAS-HIG-17-019
Search for the standard model Higgs boson decaying to two muons in pp collisions at $\sqrt{s}= $ 13 TeV
CMS Collaboration
November 2017

Abstract: A search for the standard model (SM) Higgs boson decaying to two muons is presented using data recorded by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Limits are set on the cross section of the Higgs boson decaying to two muons for mass hypotheses between 120 and 130 GeV. For a Higgs boson with a mass of 125 GeV decaying to two muons, the 95% confidence level (CL) observed (expected) upper limit on the production rate is found to be 2.64 (2.08) times the SM value. The combination with data recorded at center-of-mass energies of 7 and 8 TeV yields a 95% CL observed (expected) upper limit of 2.64 (1.89) times the SM value. This corresponds to an upper limit on the Higgs boson branching fraction to muons of 5.7$ \times 10^{-4} $, assuming the SM production cross sections.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRL 122 (2019) 021801. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The transformed BDT output distribution in data and MC. The stacked solid histograms represent the background processes, while the stacked empty histograms represent the signal distributions. The solid circular markers are the data and the statistical error associated to them.
png pdf	Figure 2: Signal model compared to MC predictions, weigthed sum of the contribution from all process and all categories (left), and for one of the best mass resolution, category 6, (right) normalised to unity.
png pdf	Figure 2-a: Signal model compared to MC predictions, weigthed sum of the contribution from all process and all categories (left), and for one of the best mass resolution, category 6, (right) normalised to unity.
png pdf	Figure 2-b: Signal model compared to MC predictions, weigthed sum of the contribution from all process and all categories (left), and for one of the best mass resolution, category 6, (right) normalised to unity.
png pdf	Figure 3: Signal-plus-background (S+B) fit (solid) and the background-only (B) component (dashed) of the dimuon mass spectrum in events from category 12 (left) with the Modified Breit-Wigner multiplied by a Bernstein polynomial (degree 4) as the functional form and category 14 (right) with the Modified Breit-Wigner functional form. The bottom panels show the dimuon mass spectrum with the fitted background component subtracted (B component subtracted).
png pdf	Figure 3-a: Signal-plus-background (S+B) fit (solid) and the background-only (B) component (dashed) of the dimuon mass spectrum in events from category 12 (left) with the Modified Breit-Wigner multiplied by a Bernstein polynomial (degree 4) as the functional form and category 14 (right) with the Modified Breit-Wigner functional form. The bottom panels show the dimuon mass spectrum with the fitted background component subtracted (B component subtracted).
png pdf	Figure 3-b: Signal-plus-background (S+B) fit (solid) and the background-only (B) component (dashed) of the dimuon mass spectrum in events from category 12 (left) with the Modified Breit-Wigner multiplied by a Bernstein polynomial (degree 4) as the functional form and category 14 (right) with the Modified Breit-Wigner functional form. The bottom panels show the dimuon mass spectrum with the fitted background component subtracted (B component subtracted).
png pdf	Figure 4: The weighted sum of individual fits to each category of the signal-plus-background fits (solid) and the background-only components (dashed). Events are weighted according to the expected signal-to-background ratio in the category to which they belong (left). The 95% CL upper limit on the signal strength modifier, $\mu $, for 13 TeV pp collisions data collected in 2016 together with the expected limit obtained in the background hypothesis and signal-plus-background hypothesis (red line) for a SM Higgs boson with $ {m_\mathrm{H}}= $125 GeV (right).
png pdf	Figure 4-a: The weighted sum of individual fits to each category of the signal-plus-background fits (solid) and the background-only components (dashed). Events are weighted according to the expected signal-to-background ratio in the category to which they belong (left). The 95% CL upper limit on the signal strength modifier, $\mu $, for 13 TeV pp collisions data collected in 2016 together with the expected limit obtained in the background hypothesis and signal-plus-background hypothesis (red line) for a SM Higgs boson with $ {m_\mathrm{H}}= $125 GeV (right).
png pdf	Figure 4-b: The weighted sum of individual fits to each category of the signal-plus-background fits (solid) and the background-only components (dashed). Events are weighted according to the expected signal-to-background ratio in the category to which they belong (left). The 95% CL upper limit on the signal strength modifier, $\mu $, for 13 TeV pp collisions data collected in 2016 together with the expected limit obtained in the background hypothesis and signal-plus-background hypothesis (red line) for a SM Higgs boson with $ {m_\mathrm{H}}= $125 GeV (right).
png pdf	Figure 5: The 95% CL upper limit on the signal strength modifier, $\mu $, for the combination of the 7, 8, and 13 TeV datasets (left) together with the expected limit obtained background hypothesis and in the signal-plus-background hypothesis (red-line) for a SM Higgs boson with $ {m_\mathrm{H}}= $ 125 GeV. The combined local p-value and significance as a function of the SM Higgs boson mass hypothesis (right). The observation (black) is compared to the expectation (red) for the Higgs boson, and (blue) for the Higgs boson mass of 125 GeV.
png pdf	Figure 5-a: The 95% CL upper limit on the signal strength modifier, $\mu $, for the combination of the 7, 8, and 13 TeV datasets (left) together with the expected limit obtained background hypothesis and in the signal-plus-background hypothesis (red-line) for a SM Higgs boson with $ {m_\mathrm{H}}= $ 125 GeV. The combined local p-value and significance as a function of the SM Higgs boson mass hypothesis (right). The observation (black) is compared to the expectation (red) for the Higgs boson, and (blue) for the Higgs boson mass of 125 GeV.
png pdf	Figure 5-b: The 95% CL upper limit on the signal strength modifier, $\mu $, for the combination of the 7, 8, and 13 TeV datasets (left) together with the expected limit obtained background hypothesis and in the signal-plus-background hypothesis (red-line) for a SM Higgs boson with $ {m_\mathrm{H}}= $ 125 GeV. The combined local p-value and significance as a function of the SM Higgs boson mass hypothesis (right). The observation (black) is compared to the expectation (red) for the Higgs boson, and (blue) for the Higgs boson mass of 125 GeV.

Tables

png pdf

Table 1:
The optimized event categories, the product of acceptance and selection efficiency ($A\epsilon $) in% for the different production processes, the expected number of SM signal events ($ {m_\mathrm{H}} = $ 125 GeV), the estimated number of background events at 125 GeV, the full width at half maximum (FWHM) of the signal peak, the background functional fit form as explained in the text and the $S/\sqrt {B}$ within FWHM.

Summary

The combination of the present results with data recorded earlier at center-of-mass energies of 7 and 8 TeV yields a 95% CL observed (expected) upper limit on the production rate of 2.64 (1.89) times the SM value. Theoretical uncertainties are considered correlated across the datasets, while the main experimental uncertainties are considered uncorrelated. The best fit signal strength is obtained for a Higgs mass of 125 GeV, $ \hat{\mu}^{\text{comb}}_{125} = $ 0.9${}^{+1.0}_{-0.9}$, and the observed (expected) combined significance at $m_{\mathrm{H}} = $125 GeV is 0.98 (1.09)$\sigma$. This corresponds to an upper limit on the $ \mathrm{H} \to \mu^{+}\mu^{-}$ branching fraction of 5.7$\times 10^{-4}$, assuming the SM production cross sections.

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