Probing the CP nature of the Higgs boson at linear colliders with tau spin correlations; the case of mixed scalar-pseudoscalar couplings

Abstract

The prospects for the measurement of the pseudoscalar admixture in the hrr coupling to a Standard Model Higgs boson of 120 GeV mass are discussed in a quantitative manner for e + e - collisions of 350 GeV centre-of-mass energy. Specific angular distributions in the h → γ + γ - , γ ± → ρ ± ν̄ γ (ν γ ) decay chain can be used to probe mixing angles of scalar-pseudoscalar hγγ couplings. In the discussion of the feasibility of the method, assumptions on the properties of a future detector for an e + e - linear collider such as TESLA are used. The Standard Model Higgsstrahlung production process is taken as an example. For the expected performance of a typical linear collider set-up, the sensitivity of a measurement of the scalar-pseudoscalar mixing angle turned out to be 6°. It will be straightforward to apply our results to estimate the sensitivity of a measurement, in cases another scenario of the Higgs boson sector (Standard Model or not) is chosen by nature. The experimental error of the method is expected to be limited by the statistics.