CP violation in a light Higgs boson decay from τ-spin correlations at a linear collider

We present a new method to measure the transverse spin correlation in the H→τ+τ− decay. The method has been devised to be insensitive to the beamstrahlung which affects the definition of the beam energy at a linear collider. In the case of two τ±→π±ν¯τ(ντ) decays, using the anticipated detector performance of the TESLA project, we get a promising estimation of the error expected on the measurement of a CP violating phase.