Probing Electroweak Phase Transition at CEPC via Exotic Higgs Decays with 4b Final States

  • Zhen Wang Tsung-Dao Lee Institute, Shanghai Jiao Tong University
  • Xuliang Zhu Tsung-Dao Lee Institute, Shanghai Jiao Tong University
  • Elham E Khoda University of Washington, Seattle
  • Shih-Chieh Hsu University of Washington, Seattle
  • Nikolaos Konstantinidis University College London
  • Ke Li University of Washington, Seattle
  • Shu Li Tsung-Dao Lee Institute, Shanghai Jiao Tong University
  • Michael J. Ramsey-Musolf University of Massachusetts, Amherst
  • Yanda Wu Tsung-Dao Lee Institute, Shanghai Jiao Tong University
  • Yuwen E. Zhang University College London
DOI: https://doi.org/10.31526/lhep.2023.436
Keywords: Electroweak phase transition, Exotics Higgs decay, Lepton collider, CEPC

Abstract

A strong first-order electroweak phase transition (EWPT) can be induced by light new physics weakly coupled
to the Higgs. This study focuses on a scenario in which the first-order EWPT is driven by a light scalar
s with a mass between 15 and 60 GeV. A search for exotic decays of the Higgs boson into a pair of spin-zero
particles, h → ss, where the s-boson decays into b-quarks promptly is presented. The search is performed
in events where the Higgs is produced in association with a Z boson, giving rise to a signature of two
charged leptons (electrons or muons) and multiple jets from b-quark decays. The analysis is considering a
scenario of analyzing 5000 fb−1 e+e− collision data at
√
s = 240 GeV from the Circular Electron Positron
Collider (CEPC). This study with 4b final state conclusively tests the expected sensitivity of probing the
light scalars in the CEPC experiment. Upper limits are set on the Higgs to double singlet cross-section times
branching ration with 95% CL. The ratio of these limits over the SM production cross-section is estimated
to be around 5 × 10−4 for the mass range of 15–60 GeV. The sensitivity reach is significantly higher than
that can be achieved at the LHC.

Author Biographies

Zhen Wang, Tsung-Dao Lee Institute, Shanghai Jiao Tong University

primary author

Xuliang Zhu, Tsung-Dao Lee Institute, Shanghai Jiao Tong University

primary author

Elham E Khoda, University of Washington, Seattle

primary author

Published
2023-10-30
Issue
Volume 2023
Section
Special Issue on Higgs Physics, and beyond, after 10 Years since the Discovery
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