Searching for Charged Higgs Bosons via $e^{+}{e}^{-}\to H^{+}{H}^{-}\to c\bar{b}\bar{c}b$ at Linear Colliders

Abstract

We study a search for the charged Higgs boson via $e^{+}{e}^{-}\to H^{+}{H}^{-}\to c\bar{b}\bar{c}b$ at the 500 GeV ILC. In a general two Higgs doublet model without $Z_2$ symmetry, extra Yukawa couplings ${\rho }_{tt}$ and ${\rho }_{tc}$ can drive baryogenesis, but searches at the HL-LHC may still go empty-handed if the couplings are relatively weak. Taking $m_{H^{+}}\simeq m_H\simeq m_A\simeq 200$ GeV, with ${\rho }_{tt}$, ${\rho }_{tc}\sim 0.1$ and no $h(125)$-$H$ mixing, $H^{+}\to c\bar{b}$ decay is dominant, and the $c\bar{b}\bar{c}b$ final state is likely overwhelmed by QCD background at the LHC. We show that the electroweak production of $H^{+}{H}^{-}$ at the ILC is discoverable with integrated luminosity of 1 ab${}^{-1}$. Furthermore, we show that $m_{H^{+}}$ can be extracted by requiring the two pairs of $b$ and light jets be roughly equal in mass, without assuming the mass value. Thus, ILC can probe low mass Higgs bosons in multijet final states to complement HL-LHC in the future

Comments: 15 pages, 6 figures