Search for invisible decays of a Higgs boson produced through vector boson fusion in proton-proton collisions at $\sqrt{s} =$ 13 TeV

Abstract: A search for invisible decays of a Higgs boson is performed using proton-proton collision data collected with the CMS detector at the LHC in 2016 at a center-of-mass energy $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The search targets the production of a Higgs boson via vector boson fusion. The data are found to be in agreement with the background contributions from standard model processes. An observed (expected) upper limit of 0.33 (0.25), at 95% confidence level, is placed on the branching fraction of the Higgs boson decay to invisible particles, assuming standard model production rates and a Higgs boson mass of 125.09 GeV. Results from a combination of this analysis and other direct searches for invisible decays of the Higgs boson, performed using data collected at $\sqrt{s} =$ 7, 8, and 13 TeV, are presented. An observed (expected) upper limit of 0.19 (0.15), at 95% confidence level, is set on the branching fraction of invisible decays of the Higgs boson. The combined limit represents the most stringent bound on the invisible branching fraction of the Higgs boson reported to date. This result is also interpreted in the context of Higgs-portal dark matter models, in which upper bounds are placed on the spin-independent dark-matter-nucleon scattering cross section.

• The paper presents a novel analysis using VBF to search for invisible Higgs decays and reports an observed (expected) upper limit of 0.33 (0.25) at 95% CL.
• The methodology employs advanced kinematic fitting and jet separation techniques to effectively distinguish signal from background in 13 TeV proton collisions.
• The study constrains Higgs-portal dark matter models by limiting the spin-independent dark matter-nucleon scattering cross section, complementing direct detection efforts.

Analysis of Invisible Higgs Boson Decays via Vector Boson Fusion

This paper presents a detailed investigation into invisible decay modes of the Higgs boson, primarily focusing on the Higgs production through vector boson fusion (VBF) in proton-proton collisions at a center-of-mass energy of 13 TeV. The data, collected using the CMS detector at the LHC in 2016, corresponds to an integrated luminosity of 35.9 fb$^-1$.

Methodology and Results

The research meticulously assesses the invisible branching fraction of the Higgs boson, assuming an SM production mass of 125.09 GeV. The strategy exploits the distinctive properties of the VBF production mechanism, characterized by two jets with large separation in pseudorapidity and significant invariant mass. The analysis incorporates advanced kinematic fitting techniques to discriminate signal from background processes effectively.

The analysis sets an observed (expected) upper limit on the invisible Higgs decay branching fraction of 0.33(0.25) at 95% confidence level (CL). Combining these results with previous data from 7 and 8 TeV, the paper reports a more stringent observed (expected) upper limit of 0.19(0.15) at 95% CL. This represents a substantial improvement over prior constraints.

Interpretation in Dark Matter Context

Significantly, the paper extends the findings to the context of Higgs-portal dark matter models. These models posit the Higgs boson as a mediator between the visible particles of the Standard Model and hypothetical dark matter candidates. Using the derived limits on the Higgs boson invisible width, the study places constraints on the spin-independent dark matter-nucleon scattering cross section.

Implications and Future Directions

The results have pivotal implications for new physics scenarios. This analysis provides constraints on theories beyond the Standard Model, particularly those involving dark matter. While direct detection experiments currently offer stringent limits on dark matter interactions for higher mass ranges, this study enhances sensitivity to lower masses, thus complementing direct detection efforts.

Future work could focus on increasing the integrated luminosity and improving detector technologies to refine these measurements further. The incorporation of advanced machine learning techniques might enhance the separation of signal and background, thereby pushing the boundaries of current limits on invisible Higgs boson decays.

Conclusion

This comprehensive study exemplifies the role of collider experiments in probing fundamental physics questions, offering insights into potential extensions of the Standard Model. The constraints derived here aid in characterizing potential dark matter interactions via the Higgs boson, illustrating the interplay between high-energy physics experiments and cosmological inquiries into dark matter. The methodologies and results presented will undoubtedly serve as a benchmark for future investigations into invisible Higgs boson decay processes.