New angles on top quark decay to a charged Higgs

To properly discover a charged Higgs Boson (H) requires its spin and couplings to be determined. We investigate how to utilize t spin correlations to analyze the H couplings in the decay t bH ⁺ bτ ⁺ ν _τ . 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 β. Using a Monte Carlo approach to simulate full hadron-level events, we evaluate systematically how the H τν _τ 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(). This method is particularly useful for determining the coupling structure of H in the large tan β limit, where differences from the SM are most significant.