The Higgs→ boverline{b} , coverline{c} , gg measurement at CEPC

Abstract

Accurately measuring the properties of the Higgs boson is one of the core physics objectives of the Circular Electron Positron Collider (CEPC). As a Higgs factory, the CEPC is expected to operate at a centre-of-mass energy of 240 GeV, deliver an integrated luminosity of 5.6 ab−1, and produce one million Higgs bosons according to the CEPC Conceptual Design Report (CDR). Combining measurements of the ℓ+ℓ−H, nu overline{nu}H , and qoverline{q}H channels, we conclude that the signal strength of Hto boverline{b}/coverline{c}/ gg can be measured with a relative accuracy (relative statistical uncertainty only) of 0.27%/4.03%/1.56%. Extrapolating to the recently released TDR operating parameters corresponding to the integrated luminosity of 20 ab−1, the relative accuracy of Hto boverline{b}/coverline{c}/ gg signal strength is 0.14%/2.13%/0.82% (relative statistical uncertainty only). We analyze the dependence of the expected accuracies on the critical detector performances: Color Singlet Identification (CSI) for the qoverline{q}H channel and flavor tagging for both nu overline{nu}H and qoverline{q}H channels. Compared to the baseline CEPC detector performance, ideal flavor tagging can increase the Hto boverline{b}/coverline{c}/ gg signal strength accuracy by 2%/63%/13% in the nu overline{nu}H channel and 35%/122%/181% in the qoverline{q}H channel. A strong dependence between the CSI performance and anticipated accuracies in qoverline{q}H channel is identified. The relevant systematic uncertainties are also discussed in this paper.