Combined measurements of Higgs boson couplings in proton-proton collisions at $\sqrt{s} =$ 13 TeV (1809.10733v2)

Abstract: Combined measurements of the production and decay rates of the Higgs boson, as well as its couplings to vector bosons and fermions, are presented. The analysis uses the LHC proton-proton collision data set recorded with the CMS detector in 2016 at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The combination is based on analyses targeting the five main Higgs boson production mechanisms (gluon fusion, vector boson fusion, and associated production with a W or Z boson, or a top quark-antiquark pair) and the following decay modes: H $\to$ $\gamma\gamma$, ZZ, WW, $\tau\tau$, bb, and $\mu\mu$. Searches for invisible Higgs boson decays are also considered. The best-fit ratio of the signal yield to the standard model expectation is measured to be $\mu$ $=$ 1.17 $\pm$ 0.10, assuming a Higgs boson mass of 125.09 GeV. Additional results are given for parametrizations with varying assumptions on the scaling behavior of the different production and decay modes, including generic ones based on ratios of cross sections and branching fractions or coupling modifiers. The results are compatible with the standard model predictions in all parametrizations considered. In addition, constraints are placed on various two Higgs doublet models.

• The paper presents combined Higgs boson coupling measurements using 35.9 fb⁻¹ of 13 TeV LHC data, reporting a best-fit signal strength of 1.17±0.10.
• It employs a profile likelihood fit that rigorously incorporates statistical and systematic uncertainties across multiple production and decay channels.
• The analysis constrains 2HDM and MSSM scenarios, reinforcing SM predictions while probing potential beyond Standard Model physics.

Overview of the CMS Higgs Boson Coupling Measurements

This paper presents a comprehensive analysis of the combined measurements of the Higgs boson couplings derived from proton-proton collision data collected by the CMS detector at the Large Hadron Collider (LHC) at a center-of-mass energy of 13 TeV. The dataset corresponds to an integrated luminosity of 35.9 fb$^{-1}$ recorded in 2016. The focus is on elucidating the production and decay rates of the Higgs boson and assessing its coupling to vector bosons and fermions. The paper synthesizes measurements across multiple Higgs boson production mechanisms, including gluon fusion (ggF), vector boson fusion (VBF), and associated production with $W$ or $Z$ bosons or a top-quark pair. The analysis considers decay modes such as $\text{H} \rightarrow \gamma\gamma$, $\text{ZZ}$, $\text{WW}$, $\tau\tau$, $b\bar{b}$, and $\mu\mu$, while also accounting for the possibility of invisible decays.

The paper reports a best-fit signal yield ratio to the Standard Model (SM) expectation ($\mu$) of 1.17 ± 0.10, given a Higgs boson mass of 125.09 GeV. This result is compatible with SM predictions across all parametrizations assessed, and constraints are placed on various two Higgs doublet models (2HDM).

Key Findings and Methodological Approach

1. Statistical and Systematic Treatment: The combination of results employs a profile likelihood fit combining vast categories from different analyses in a statistically consistent framework. The analysis takes into account correlations among systematic uncertainties, including theoretical uncertainties on cross-section predictions and calibration factors such as jet energy scale and b-tagging efficiency.
2. Signal Strength Measurements: The paper provides detailed insights into per-production and per-decay signal strength modifiers. The observed precision improvements in the 13 TeV dataset allow for tighter constraints than those obtained in previous runs at lower energies, primarily due to increased signal cross sections and reduced theoretical uncertainties at higher collision energies.
3. Cross-Section Ratios and Coupling Modifiers: The paper employs a generalized $\kappa$-framework to quantify deviations in coupling strengths from SM expectations, both under the assumption of effective loops and resolved loops describing processes like ggF and $\gamma\gamma$ decays. This framework is crucial for probing potential Beyond Standard Model (BSM) physics.
4. Benchmark Constraints on 2HDM and MSSM: The research extends to evaluate constraints on possible BSM scenarios involving an additional Higgs doublet. This includes investigating variations in coupling scenarios such as Type I, II, III, and IV 2HDMs, and the minimal supersymmetric standard model (MSSM) in the hMSSM scenario, providing a broader landscape to explore new physics.

Implications and Future Directions

The measurements reinforce the SM’s predictions and suggest that any potential BSM effects manifest within the current sensitivity bounds. The improved precision in determining Higgs boson properties plays a pivotal role in exploring the electroweak symmetry breaking mechanism and enhances the constraints on new physics models. The research illustrates the LHC's capability to provide critical insights into the Higgs boson's interactions, aiding the development of refined theoretical models.

The paper suggests avenues for future developments in phenomenology and experimental analysis, including enhanced sensitivity to Higgs decays into second-generation fermions and tighter constraints on BSM models. Fully exploiting higher luminosity datasets and potential future upgrades at the LHC will further refine these measurements.