How well can we reconstruct the $t\bar{t}$ system near its threshold at future ee linear colliders?

Abstract.

We developed a new method for the full kinematical reconstruction of the $t\bar{t}$ system near its threshold at future linear e ⁺ e ^- colliders. In the core of the method lies likelihood fitting which is designed to improve measurement accuracies of the kinematical variables that specify the final states resulting from $t\bar{t}$ decays. The improvement is demonstrated by applying this method to a Monte Carlo $t\bar{t}$ sample generated with various experimental effects including beamstrahlung, finite acceptance and resolution of the detector system, etc. In most cases the fit takes a broad non-Gaussian distribution of a given kinematical variable to a nearly Gaussian shape, thereby justifying phenomenological analyses based on simple Gaussian smearing of the parton-level momenta. The standard deviations of the resultant distributions of various kinematical variables are given in order to facilitate such phenomenological analyses. A possible application of the kinematical fitting method and its expected impact are also discussed.