The high-precision measurement of Higgs boson properties is one of the primary goals of the Circular Electron Positron Collider (CEPC). The measurements of 
					 decay branching fraction in the CEPC experiment is presented, considering a scenario of analysing 5000 fb-1 collision data with the center-of-mass energy of 250 GeV. In this study the Higgs bosons are produced in association with a pair of leptons, dominantly mediated by the ZH production process. The statistical uncertainty of the signal cross section is estimated to be about 1% in the 
					 final state, and approximately 5%-10% in the 
					 final states. In addition, the main sources of the systematic uncertainties and their impacts to the measurements of branching fractions are discussed. This study demonstrates the potential of precise measurement of the hadronic final states of the Higgs boson decay at the CEPC, and will provide key information to understand the Yukawa couplings between the Higgs boson and quarks, which are predicted to be the origin of quarks’ masses in the standard model.
				

China

Yu Bai

United States

Chun-Hui Chen

Ya-Quan Fang

Gang Li

Man-Qi Ruan

United Kingdom

Jing-Yuan Shi

Bo Wang

Pan-Yu Kong

Bo-Yang Lan

Zhan-Feng Liu

Measurements of decay branching fractions of 
					 in associated 
					 production at the CEPC Supported by the National Key Program for S&T Research and Development (2016YFA0400400), National Natural Science Foundation of China (NSFC) (11705028), Fundamental Research Funds for the Central Universities (2242015K40027 and 2242017K40018), Provincial Innovation and Entrepreneurship Training Program for Undergraduate (201710286068X), and Beijing Municipal Science and Technology Commission project (Z181100004218003)

As a Higgs factory, the CEPC (Circular Electron-Positron Collider) project aims at precision measurements of the Higgs boson properties. A baseline detector concept, APODIS (A PFA Oriented Detector for the HIggS factory), has been proposed for the CEPC CDR (Conceptual Design Report) study. We explore the Higgs signatures for this baseline design with Higgs events. The detector performance for reconstructing charged particles, photons and jets is quantified with and jet final states, respectively. The resolutions of reconstructed Higgs boson mass are comparable for the different decay modes with jets in the final states. We also analyze the * and ZZ* decay modes, where a clear separation between different decay cascades is observed.

Hang Zhao

Yong-Feng Zhu

Cheng-Dong Fu

Dan Yu

The Higgs signatures at the CEPC CDR baseline Supported by National Key Program for S&amp;T Research and Development (2016YFA0400400), the National Natural Science Foundation of China (11675202), and the Hundred Talent programs of Chinese Academy of Science (Y3515540U1)

The Circular Electron-Positron Collider (CEPC) is a future Higgs factory proposed by the Chinese high energy physics community. It is planned to operate at a center-of-mass energy of 240–250 GeV and is expected to accumulate an integrated luminosity of 5 ab−1 over ten years of operation. At the CEPC, Higgs bosons will be dominantly produced from the ZH associated process. The vast number of Higgs events collected will enable precise studies of its properties, including Yukawa couplings to massive particles. With GEANT4-based simulation of detector effects, we study the feasibility of measuring the Higgs boson decaying into a pair of muons at the CEPC. The results with and without information from the Z boson decay products are provided, showing that a signal significance of over 10 standard deviations can be achieved and the H-μ-μ coupling can be measured within 10% accuracy.

Zhen-Wei Cui

Qiang Li

Lei Wang

Da-Neng Yang

Measurement of H → μ+ μ− production in association with a Z boson at the CEPCSupported by National Natural Science Foundation of China (11475190, 11575005), CAS Center for Excellence in Particle Physics (CCEPP) and CAS Hundred Talent Program (Y3515540U1)

The Circular Electron Positron Collider (CEPC) is a future Higgs factory proposed by the Chinese high energy physics community. It will operate at a center-of-mass energy of 240–250 GeV. The CEPC will accumulate an integrated luminosity of 5 ab−1 over ten years of operation, producing one million Higgs bosons via the Higgsstrahlung and vector boson fusion processes. This sample allows a percent or even sub-percent level determination of the Higgs boson couplings. With GEANT4-based full simulation and a dedicated fast simulation tool, we have evaluated the statistical precisions of the Higgstrahlung cross section σZH and the Higgs mass mH measurement at the CEPC in the Z → μ+μ− channel. The statistical precision of σZH (mH) measurement could reach 0.97% (6.9 MeV) in the model-independent analysis which uses only the information from Z boson decays. For the standard model Higgs boson, the mH precision could be improved to 5.4 MeV by including the information from Higgs decays. The impact of the TPC size on these measurements is investigated. In addition, we studied the prospect of measuring the Higgs boson decaying into invisible final states at the CEPC. With the Standard Model ZH production rate, the upper limit of could reach 1.2% at 95% confidence level.

Zhen-Xing Chen

Ying Yang

Da-Yong Wang

Shan Jin

Yong Ban

Cross section and Higgs mass measurement with Higgsstrahlung at the CEPC Supported by the Joint Funds of the NSFC (U1232105) and CAS Hundred Talent Program (Y3515540U1)

The cross sections of the Higgs production and the corresponding backgrounds of e+e− annihilations at the CEPC (Circular Electron and Positron Collider) are calculated by a Monte-Carlo method, and the beamstrahlung effect at the CEPC is carefully investigated. The numerical results and the expected number of events for the CEPC are provided.

Xin Mo

Xin-Chou Lou

Physics cross sections and event generation of e+e− annihilations at the CEPCSupported by CAS/SAFEA International Partnership Program for Creative Research Teams, and funding from CAS and IHEP for the Thousand Talent and Hundred Talent programs, as well as grants from the State Key Laboratory of Nuclear Electronics and Particle Detectors

The surprisingly large value of r , the ratio of power in tensor to scalar density perturbations in the CMB reported by the BICEP2 Collaboration, if confirmed, provides strong evidence for Inflation at the GUT scale. While the Inflationary signal remains the best motivated source, a large value of r alone would still allow for the possibility that a comparable gravitational wave background might result from a self ordering scalar field (SOSF) transition that takes place later at somewhat lower energy. We find that even without detailed considerations of the predicted BICEP signature of such a transition, simple existing limits on the isocurvature contribution to CMB anisotropies would definitively rule out a contribution of more than 5% to râ0.2 . We also present a general relation for the allowed fractional SOSF contribution to r as a function of the ultimate measured value of r . These results point strongly not only to an inflationary origin of the BICEP2 signal, if confirmed, but also to the fact that if the GUT scale is of order 1016Â GeV then either the GUT transition happens before Inflation or the Inflationary transition and the GUT transition must be one and the same.