New angles on top quark decay to a charged Higgs

TL;DR

This paper explores how to analyze the spin and couplings of a charged Higgs boson in top quark decays using spin correlations and Monte Carlo simulations, especially focusing on large $ aneta$ scenarios.

Contribution

It introduces a method to determine the $H^$ couplings via spin correlations in top decays within a Two-Higgs-Doublet Model, emphasizing azimuthal angle observables.

Findings

Azimuthal angle correlations are effective for spin analysis.

The method is most sensitive at large $ aneta$ values.

Monte Carlo simulations support the feasibility of the approach.

Abstract

To properly discover a charged Higgs Boson ($H^\pm$) requires its spin and couplings to be determined. We investigate how to utilize $\ttbar$ spin correlations to analyze the $H^\pm$ couplings in the decay $t\to bH^+\to b\tau^+\nu_\tau$. Within the framework of a general Two-Higgs-Doublet Model, we obtain results on the spin analyzing coefficients for this decay and study in detail its spin phenomenology, focusing on the limits of large and small values for $\tan\beta$. Using a Monte Carlo approach to simulate full hadron-level events, we evaluate systematically how the $H^\pm\to\tau^\pm\nu_\tau$ decay mode can be used for spin analysis. The most promising observables are obtained from azimuthal angle correlations in the transverse rest frames of $t(\bar{t})$. This method is particularly useful for determining the coupling structure of $H^\pm$ in the large $\tan\beta$ limit, where differences from the SM are most significant.