Determining the CP parity of Higgs bosons at the LHC in the τ to 1-prong decay channels

We propose a method for determining the CP nature of a neutral Higgs boson or spin-zero resonance ϕ   at the CERN Large Hadron Collider (LHC) in its ϕ→τ−τ+ϕ→τ−τ+ decay channel. The method can be applied to any 1-prong τ-decay mode, which comprise the majority of the τ-lepton decays. The proposed observables allow to discriminate between pure scalar and pseudoscalar Higgs-boson states and/or between a CP-conserving and CP  -violating Higgs sector. We show for the decays τ→πνττ→πντ that the method maintains its discriminating power when measurement uncertainties are taken into account. The method will be applicable also at a future linear e+e−e+e− collider.