New angles on top quark decay to a charged Higgs Boson

Top quarks produced in pairs are predicted to experience spin correlations. Due to the large tt statistics expected for the LHC, it should be possible to search for new physics effects in angular variables sensitive to these correlations. We investigate, for a general two-Higgs Doublet Model (2HDM), the charged Higgs boson decay of the top quark through the channel t → bH → bτντ . Analytic results are presented on the spin analyzing coefficients for this decay mode. We then explore in some detail the correlation phenomenology in the Type II 2HDM. Finally we present a hadron-level Monte Carlo analysis, illustrating distributions in azimuthal angles which are sensitive to correlations in the transverse plane. These observables are accessible also in the τ channel, and are therefore particularly interesting for analyzing the t → bH decay. 1 Spin correlations in tt hadroproduction When top quarks are pair-produced in a hadronic collision, the spin projections of the t and the t can be correlated to a certain degree when a suitable basis is chosen for spin quantization. There exists an extensive earlier literature on this topic; see for example [1–3], or the more recent review [4]. The degree of tt̄ spin correlation can be expressed as C(â, b̂) = 4 〈