Top quark mass definition and t(t)over-bar production near threshold at the Next Linear Collider - art. no. 074012

We suggest an infrared-insensitive quark mass, defined by subtracting the s oft part of the quark self-energy from the pole mass. We demonstrate the de ep relation of this definition with the static quark-antiquark- potential. At leading order in 1/m this mass coincides with the PS mass which is defin ed in a completely different manner. Going beyond the static limit, the sma ll normalization point introduces recoil corrections which are calculated h en as well. Using this mass concept and other concepts for the quark mass w e calculate the cross section of e(+)e(-) --> t (t) over bar near threshold at NNLO accuracy adopting three alternative approaches; namely, (1) fixing the pole mass, (2) fixing the PS mass, and (3) fixing the new mass which w e call the (PS) over bar mass. We demonstrate that perturbative predictions for the cross section become much more stable if we use the PS or the PS m ass for the calculations. A careful analysis suggests that the top quark ma ss can be extracted from a threshold scan at NLC with an accuracy of about 100-200 MeV.