Transverse spin effects in H/A ->tau(+)tau(-); tau(+/-)->nu X-+/- Monte Carlo approach

Abstract

The transverse spin effects may be helpful to distinguish between scalar (J PC = 0++) or pseudoscalar (J PC = 0- + ) nature of the spin zero (Higgs) particle once discovered in future accelerator experiments. The correlations can manifest themselves e.g. in the distribution of acollinearity angle of X ± in the decay chain H/A -A t + t - ; t 1*1 —¥ p X ± . This delicate measurement will require, however, reconstruction of the Higgs boson rest-frame. Then, questions of the combined detection-theoretical effects may be critical to establish the reliability of the method. An appropriate Monte Carlo program is essential. To make such studies possible we have extended the standard universal interface of the TAU0LA r-lepton decay library to include the complete spin effects for r leptons originating from the spin zero particle. The interface is expected to work with any Monte Carlo generator providing Higgs boson production and subsequent decay into a pair of r leptons. Examples of numerical results and cross checks of the program will be also given. In particular, we find th a t effects of beamstrahlung may be critical to the quality of the measurement of the Higgs boson, unless some improvements of the method can be found.