Searching for Charged Higgs Boson in Polarized Top Quark

TL;DR

This paper investigates the potential to detect heavy charged Higgs bosons via top-quark polarization measurements in specific production channels within the Type-II Two-Higgs-Doublet-Model, highlighting the sensitivity to the parameter tanβ.

Contribution

It provides a detailed analysis of top-quark polarization as a probe for tanβ in charged Higgs boson production, especially in the decay channel, using helicity amplitude calculations.

Findings

Top-quark polarization from charged Higgs decay effectively measures tanβ.

Production channels have different sensitivities to top-quark polarization.

Helicity amplitude calculations support the feasibility of this measurement.

Abstract

The charged Higgs boson is quite common in many new physics models. In this study we examine the potential of observing a heavy charged Higgs boson in its decay mode of top-quark and bottom-quark in the Type-II Two-Higgs-Doublet-Model. In this model, the chirality structure of the coupling of charged Higgs boson to the top- and bottom-quark is very sensitive to the value of $\tan\beta$. As the polarization of the top-quark can be measured experimentally from the top-quark decay products, one could make use of the top-quark polarization to determine the value of $\tan\beta$. We preform a detailed analysis of measuring top-quark polarization in the production channels $gb\to tH^-$ and $g\bar{b}\to \bar{t}H^+$. We calculate the helicity amplitudes of the charged Higgs boson production and decay.Our calculation shows that the top-quark from the charged Higgs boson decay provides a good probe for measuring $\tan\beta$, especially for the intermediate $\tan\beta$ region. On the contrary, the top-quark produced in association with the charged Higgs boson cannot be used to measure $\tan\beta$ because its polarization is highly contaminated by the $t$-channel kinematics.