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

TL;DR

This paper demonstrates that the International Linear Collider (ILC) can effectively discover and measure low-mass charged Higgs bosons decaying into charm and bottom quarks, providing a complementary approach to the LHC.

Contribution

It shows that the ILC can detect charged Higgs bosons in multijet final states and determine their mass without prior assumptions, especially when LHC searches are limited.

Findings

ILC can discover charged Higgs bosons with 1 ab$^{-1}$ luminosity.

Mass of $H^+$ can be extracted without prior mass assumptions.

Charged Higgs decay $H^+ o car{b}$ dominates in the studied parameter space.

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