The $Higgs\to b\bar{b},c\bar{c},gg$ 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 $240GeV$, deliver an integrated luminosity of $5.6a{b}^{-1}$, and produce one million Higgs bosons according to the CEPC Conceptual Design Report (CDR). Combining measurements of the ${\ell }^{+}{\ell }^{-}H$, $\nu \bar{\nu }H$, and $q\bar{q}H$ channels, we conclude that the signal strength of $H\to b\bar{b}/c\bar{c}/gg$ can be measured with a relative accuracy (statistic uncertainty only) of 0.27\%/4.03\%/1.56\%. Extrapolating to the recently released TDR operating parameters corresponding to the integrated luminosity of $20a{b}^{-1}$, the relative accuracy of $H\to b\bar{b}/c\bar{c}/gg$ signal strength is 0.14\%/2.13\%/0.82\%. We analyze the dependence of the expected accuracies on the critical detector performances: Color Singlet Identification (CSI) for the $q\bar{q}H$ channel and flavor tagging for both $\nu \bar{\nu }H$ and $q\bar{q}H$ channels. We observe that compared to the baseline CEPC detector performance, ideal flavor tagging increases the $H\to b\bar{b}/c\bar{c}/gg$ signal strength accuracy by 2\%/63\%/13\% in the $\nu \bar{\nu }H$ channel and 35\%/122\%/181\% in the $q\bar{q}H$ channel. In addition, better performance of CSI can significantly improve the anticipated accuracy of signal strength. The relevant systematics are also discussed in this paper.