- The paper observes the Higgs boson decay to bottom quarks with a 58% branching fraction, directly confirming the Yukawa coupling to down-type quarks.
- It employs advanced b jet identification and multivariate discriminant techniques on CMS data at 13 TeV to efficiently extract the signal.
- The findings reinforce the Standard Model predictions and establish a robust method for future searches of rare decay processes and potential new physics.
Analysis of Higgs Boson Decay to Bottom Quarks
The study presented in the paper observes the Standard Model (SM) Higgs boson's decay into a pair of bottom quarks (b quarks), a critical mode given its predicted 58% branching fraction at a Higgs mass of approximately 125 GeV. This decay mode is notable for substantiating the Yukawa coupling of the Higgs boson to down-type quarks, providing insights into the Higgs mechanism's role in mass generation within the charged fermion sector of the SM.
Methodology and Data
The analysis exploits data recorded by the CMS detector in 2017 at the Large Hadron Collider, involving proton-proton collision events at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 41.3 fb−1. The study focuses on processes where Higgs bosons are produced alongside a W or Z boson, selecting final states with 0, 1, or 2 leptons and two b quark jets. The process captures signal and background interplay using improved b jet identification algorithms and advanced multivariate discriminant techniques, yielding a more efficient signal extraction from substantial background noise.
Results and Interpretation
The analysis reveals an excess of events consistent with the Higgs boson decay to b quarks with a significance of 4.8 standard deviations when combined with earlier measurements. The observed signal strength stands at 1.01 ± 0.22, compared to a SM expectation of 4.9 standard deviations, indicating an agreement within experimental uncertainties.
Additionally, the paper highlights the methodology's validation by observing a process analogous to the Higgs production but involving dibosons (WW, WZ, ZZ) with similar event final states. The methodology's consistency and robustness are supported by this observation, which achieved a significance of 5.2 standard deviations.
Implications and Future Directions
The confirmation of the Higgs boson decay channel to b quarks is crucial for validating the Higgs mechanism in the SM, especially regarding fermion mass generation through Yukawa couplings. The observed concordance with SM predictions reinforces existing theoretical paradigms but simultaneously tightens constraints on potential new physics beyond the SM.
Practically, these findings underscore the efficacy of the CMS detector's capabilities and the data analysis frameworks employed, offering a framework applicable to further searches of rare decay processes and new physics phenomena. The research paves the way for future explorations into areas of electroweak symmetry breaking, potential deviations from SM predictions, and investigations into less prevalent Higgs decay modes under increased collision energies and luminosities.
This paper demonstrates the continuous advancement in particle detection and data analysis at LHC experiments, which are essential for probing the SM's limits and seeking evidence for new theoretical frameworks. The results exemplify a methodological template for future inquiries into Higgs interactions, critical for the ongoing evolution of particle physics.
