Measuring the charged Higgs mass and distinguishing between models with top-quark observables

We study the process of single-top production in association with a charged Higgs boson at the LHC and discuss how top-quark polarization and an azimuthal asymmetry $A_\varphi$ of the charged lepton from top decay can be used in some extensions of the Standard Model to determine or constrain the charged Higgs boson mass. We also discuss some scenarios where these variables can be used to distinguish between different models.