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

The prospects for the measurement of the pseudoscalar admixture in the h tau tau T 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 --> tau(+)tau(-), tau(+/-) --> rho(+/-)(ν) over bar (tau) (nu(tau)) decay chain can be used to probe mixing angles of scalar-pseudoscalar htautau 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 6degrees. 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. (C) 2003 Elsevier B.V. All rights reserved.