Measurements of decay branching fractions of the Higgs boson to hadronic final states at the CEPC

Abstract

The Circular Electron Positron Collider (CEPC) is a large-scale particle accelerator designed to collide electrons and positrons at high energies. One of its primary goals is to achieve high-precision measurements of the properties of the Higgs boson and is facilitated by the large number of Higgs bosons that are produced with significantly low contamination. The measurements of Higgs boson branching fractions into and , where the W or Z bosons decay hadronically, are presented in the context of the CEPC experiment, assuming a scenario with 5600 fb−1 of collision data at a center-of-mass energy of 240 GeV. In this study the Higgs bosons are produced in association with a Z boson, with the Z boson decaying into a pair of muons , which have high efficiency and resolution. To separate all decay channels simultaneously with high accuracy, the Particle Flow Network (PFN), a graph-based machine learning model, is considered. The precise classification provided by the PFN is employed in measuring the branching fractions using the migration matrix method, which accurately corrects for detector effects in each decay channel. The statistical uncertainty of the measured branching ratio is estimated to be 0.55% in the final state and approximately 1.5% − 16% in the final states. In addition, the main sources of systematic uncertainties in the measurement of the branching fractions are discussed.